WorldWideScience

Sample records for attosecond photoelectron spectroscopy

  1. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, I.; Huppert, M.; Wörner, H. J., E-mail: hwoerner@ethz.ch [Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich (Switzerland); Brown, M. A. [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich (Switzerland); Bokhoven, J. A. van [Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1, 8093 Zurich (Switzerland); Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, 5232 Villigen (Switzerland)

    2015-12-15

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  2. Secondary-electron cascade in attosecond photoelectron spectroscopy from metals

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2009-01-01

    Attosecond spectroscopy is currently restricted to photon energies around 100 eV. We show that under these conditions, electron-electron scatterings, as the photoelectrons leave the metal, give rise to a tail of secondary electrons with lower energies and hence a significant background. We develop...

  3. Polarization Effects in Attosecond Photoelectron Spectroscopy

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2010-01-01

    following the field instead. We show that polarization effects may lead to an apparent temporal shift that needs to be properly accounted for in the analysis. The effect may be isolated and studied by angle-resolved photoelectron spectroscopy from oriented polar molecules. We also show that polarization...

  4. Attosecond photoelectron spectroscopy of electron transport in solids

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, Elisabeth

    2011-03-31

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  5. A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, E.; Stanislawski, M.; Uphues, Th. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Neppl, S.; Barth, J. V.; Menzel, D.; Feulner, P. [Physik Department E20, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Cavalieri, A. L. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Max-Planck Research Department for Structural Dynamics, Universitaet Hamburg, Notkestrasse 85, 22607 Hamburg (Germany); Bothschafter, E. M.; Ernstorfer, R.; Kienberger, R. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Physik Department E11, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Hofstetter, M.; Kleineberg, U.; Krausz, F. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet Muenchen, Fakultaet fuer Physik, Am Coulombwall 1, 85748 Garching (Germany)

    2011-06-15

    We describe an apparatus for attosecond photoelectron spectroscopy of solids and surfaces, which combines the generation of isolated attosecond extreme-ultraviolet (XUV) laser pulses by high harmonic generation in gases with time-resolved photoelectron detection and surface science techniques in an ultrahigh vacuum environment. This versatile setup provides isolated attosecond pulses with photon energies of up to 140 eV and few-cycle near infrared pulses for studying ultrafast electron dynamics in a large variety of surfaces and interfaces. The samples can be prepared and characterized on an atomic scale in a dedicated flexible surface science end station. The extensive possibilities offered by this apparatus are demonstrated by applying attosecond XUV pulses with a central photon energy of {approx}125 eV in an attosecond streaking experiment of a xenon multilayer grown on a Re(0001) substrate.

  6. Attosecond streaking of photoelectron emission from disordered solids

    CERN Document Server

    Okell, W A; Fabris, D; Arrell, C A; Hengster, J; Ibrahimkutty, S; Seiler, A; Barthelmess, M; Stankov, S; Lei, D Y; Sonnefraud, Y; Rahmani, M; Uphues, Th; Maier, S A; Marangos, J P; Tisch, J W G

    2014-01-01

    Attosecond streaking of photoelectrons emitted by extreme ultraviolet light has begun to reveal how electrons behave during their transport within simple crystalline solids. Many sample types within nanoplasmonics, thin-film physics, and semiconductor physics, however, do not have a simple single crystal structure. The electron dynamics which underpin the optical response of plasmonic nanostructures and wide-bandgap semiconductors happen on an attosecond timescale. Measuring these dynamics using attosecond streaking will enable such systems to be specially tailored for applications in areas such as ultrafast opto-electronics. We show that streaking can be extended to this very general type of sample by presenting streaking measurements on an amorphous film of the wide-bandgap semiconductor tungsten trioxide, and on polycrystalline gold, a material that forms the basis of many nanoplasmonic devices. Our measurements reveal the near-field temporal structure at the sample surface, and photoelectron wavepacket te...

  7. Theory of attosecond absorption spectroscopy in krypton

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Lindroth, Eva; Madsen, Lars Bojer

    2012-01-01

    A theory for time-domain attosecond pump–attosecond probe photoabsorption spectroscopy is formulated and related to the atomic response. The theory is illustrated through a study of attosecond absorption spectroscopy in krypton. The atomic parameters entering the formulation such as energies...... of the hole in this manner. In a second example, a hole is created in an inner shell by the first pulse, and the second probe pulse couples an even more tightly bound state to that hole. The hole decays in this example by Auger electron emission, and the absorption spectroscopy follows the decay of the hole...

  8. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy

    Science.gov (United States)

    Ramasesha, Krupa; Leone, Stephen R.; Neumark, Daniel M.

    2016-05-01

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions.

  9. Use of photoelectron laser phase determination method for attosecond measurements with quantum-mechanical calculations

    Institute of Scientific and Technical Information of China (English)

    Ge Yu-Cheng

    2008-01-01

    This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural properties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle.

  10. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons

    Science.gov (United States)

    Kowalewski, Markus; Bennett, Kochise; Rouxel, Jérémy R.; Mukamel, Shaul

    2016-07-01

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences. We demonstrate how streaked photoelectrons offer a novel tool for monitoring nonadiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can provide high time resolution direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  11. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons.

    Science.gov (United States)

    Kowalewski, Markus; Bennett, Kochise; Rouxel, Jérémy R; Mukamel, Shaul

    2016-07-22

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences. We demonstrate how streaked photoelectrons offer a novel tool for monitoring nonadiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can provide high time resolution direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  12. Tracing attosecond electron motion inside a molecule by interferences from photoelectron emission

    Energy Technology Data Exchange (ETDEWEB)

    Xu Minghui; Peng Liangyou; Zhang Zheng; Gong Qihuang, E-mail: liangyou.peng@pku.edu.cn, E-mail: qhgong@pku.edu.cn [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)

    2011-01-28

    We present a theoretical study of photoelectron emission of a homonuclear molecule by an attosecond xuv pulse, which can be regarded as a natural double-slit experiment. We show that attosecond electron motion inside the molecule opens one to two 'slits' for photoionization. Interference fringes in the angle-resolved photoelectron momentum distributions exhibit varying visibility (V), depending on the degree of which-path information (P). The complementarity relation, P{sup 2} + V{sup 2} {<=} 1, is verified in the time-dependent molecule double-slit experiment. Hence, the electron motion can be easily mapped out by measuring the interference visibility. This opens up the prospect of employing interferometric techniques to probe ultrafast intramolecular electronic motions. (fast track communication)

  13. Photoelectron photoion molecular beam spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Trevor, D.J.

    1980-12-01

    The use of supersonic molecular beams in photoionization mass spectroscopy and photoelectron spectroscopy to assist in the understanding of photoexcitation in the vacuum ultraviolet is described. Rotational relaxation and condensation due to supersonic expansion were shown to offer new possibilities for molecular photoionization studies. Molecular beam photoionization mass spectroscopy has been extended above 21 eV photon energy by the use of Stanford Synchrotron Radiation Laboratory (SSRL) facilities. Design considerations are discussed that have advanced the state-of-the-art in high resolution vuv photoelectron spectroscopy. To extend gas-phase studies to 160 eV photon energy, a windowless vuv-xuv beam line design is proposed.

  14. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons

    CERN Document Server

    Kowalewski, Markus; Rouxel, Jérémy R; Mukamel, Shaul

    2016-01-01

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry an additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences and demonstrate how it offers a novel tool to monitor non-adiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can enhance the time resolution and provide direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  15. Photoelectron spectroscopy principles and applications

    CERN Document Server

    Hüfner, Stefan

    1995-01-01

    Photoelectron Spectroscopy presents an up-to-date introduction to the field by treating comprehensively the electronic structures of atoms, molecules, solids and surfaces Brief descriptions are given of inverse photoemission, spin-polarized photoemission and photoelectron diffraction Experimental aspects are considered throughout the book, and the results are carefully interpreted by theory A wealth of measured data is presented in the form of tables for easy use by experimentalists

  16. Attosecond dynamics through a Fano resonance: Monitoring the birth of a photoelectron

    Science.gov (United States)

    Gruson, V.; Barreau, L.; Jiménez-Galan, Á.; Risoud, F.; Caillat, J.; Maquet, A.; Carré, B.; Lepetit, F.; Hergott, J.-F.; Ruchon, T.; Argenti, L.; Taïeb, R.; Martín, F.; Salières, P.

    2016-11-01

    The dynamics of quantum systems are encoded in the amplitude and phase of wave packets. However, the rapidity of electron dynamics on the attosecond scale has precluded the complete characterization of electron wave packets in the time domain. Using spectrally resolved electron interferometry, we were able to measure the amplitude and phase of a photoelectron wave packet created through a Fano autoionizing resonance in helium. In our setup, replicas obtained by two-photon transitions interfere with reference wave packets that are formed through smooth continua, allowing the full temporal reconstruction, purely from experimental data, of the resonant wave packet released in the continuum. In turn, this resolves the buildup of the autoionizing resonance on an attosecond time scale. Our results, in excellent agreement with ab initio time-dependent calculations, raise prospects for detailed investigations of ultrafast photoemission dynamics governed by electron correlation, as well as coherent control over structured electron wave packets.

  17. State-of-the-art attosecond metrology

    Energy Technology Data Exchange (ETDEWEB)

    Schultze, M., E-mail: martin.schultze@mpq.mpg.de [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Wirth, A.; Grguras, I.; Uiberacker, M.; Uphues, T.; Verhoef, A.J.; Gagnon, J. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Hofstetter, M.; Kleineberg, U. [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Goulielmakis, E. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Krausz, F. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany)

    2011-04-15

    Research highlights: {yields} We present a complete setup for investigations with attosecond temporal resoultion. {yields} Few-cycle visible laser pulses are used to generate xray pulses approaching the atomic unit of time. {yields} Attosecond XUV pulses explore ultrafast electronic dynamics in atoms. - Abstract: Tracking and controlling electron dynamics in the interior of atoms, molecules as well as in solids is at the forefront of modern ultrafast science . Time-resolved studies of these dynamics require attosecond temporal resolution that is provided by an ensemble of techniques consolidated under the term 'attosecond metrology'. This work reports the development and commissioning of what we refer to as next-generation attosecond beamline technology: the AS-1 attosecond beamline at the Max-Planck Institute of Quantum Optics. It consists of a phase-stabilized few-cycle laser system, for the generation of XUV radiation, and modules tailored for the spectral filtering and isolation of attosecond pulses as well as for their temporal characterization. The setup produces the shortest attosecond pulses demonstrated to date and combines them with advanced spectroscopic instrumentation (electron-, ion- and XUV-spectrometers). These pulses serve as temporally confined trigger events (attosecond streaking and tunneling spectroscopy) or probe pulses (attosecond absorption and photoelectron spectroscopy) enabling attosecond chronoscopy to be applied to a broad range of systems belonging to the microcosm.

  18. Two attosecond pulse transient absorption spectroscopy and extraction of the instantaneous AC Stark shift in helium

    Science.gov (United States)

    Bækhøj, Jens E.; Bojer Madsen, Lars

    2016-07-01

    In two attosecond pulse absorption spectroscopy (TAPAS) the use of two attosecond XUV pulses allows the extraction of atomic and molecular quantum mechanical dipole phases from spectroscopic measurements. TAPAS relies on interference between processes that individually only include a single XUV photon, and therefore does not rely on high intensity attosecond pulses. To show the usefulness and limitations of the TAPAS method we investigate its capability of capturing the instantaneous AC Stark shift induced by a midinfrared 3200 nm pulse in the | 1{{s}}2{{p}}> state of helium.

  19. Photoelectron spectroscopy of phthalocyanine vapors

    Energy Technology Data Exchange (ETDEWEB)

    Berkowitz, J.

    1979-01-01

    The He(I) photoelectron spectra of several metal phthalocyanines and metal-free phthalocyanine vapor shows that: a sharp peak at 4.99 eV is an artifact due to ionization of atomic He by He(II) radiation; the first phthalocyanine peak (metal-containing or metal-free) occurs at 6.4 eV; and the metal-like d orbitals lie at least 1 to 2 eV deeper, except in the case of Fe. (DLC)

  20. Imaging plasmonic fields near gold nanospheres in attosecond time-resolved streaked photoelectron spectra

    Science.gov (United States)

    Li, Jianxiong; Thumm, Uwe

    2016-05-01

    To study time-resolved photoemission from gold nanospheres, we introduce a quantum-mechanical approach, including the plasmonic near-field-enhancement of the streaking field at the surface of the nanosphere. We use Mie theory to calculate the plasmonically enhanced fields near 10 to 200 nm gold nanospheres, driven by incident near infrared (NIR) or visible laser pulses. We model the gold conduction band in terms of a spherical square well potential. Our simulated streaked photoelectron spectra reveal a plasmonic amplitude enhancement and phase shift related to calculations that exclude the induced plasmonic field. The phase shift is due to the plasma resonance. This suggests the use of streaked photoelectron spectroscopy for imaging the dielectric response and plasmonic field near nanoparticles. Supported by the NSD-EPSCoR program, NSF, and the USDoE.

  1. Photoelectron spectroscopy of heavy atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    White, M.G.

    1979-07-01

    The importance of relativistic interactions in the photoionization of heavy atoms and molecules has been investigated by the technique of photoelectron spectroscopy. In particular, experiments are reported which illustrate the effects of the spin-orbit interaction in the neutral ground state, final ionic states and continuum states of the photoionization target.

  2. Photoelectron Spectroscopy in Advanced Placement Chemistry

    Science.gov (United States)

    Benigna, James

    2014-01-01

    Photoelectron spectroscopy (PES) is a new addition to the Advanced Placement (AP) Chemistry curriculum. This article explains the rationale for its inclusion, an overview of how the PES instrument records data, how the data can be analyzed, and how to include PES data in the course. Sample assessment items and analysis are included, as well as…

  3. Spectroscopy of transient neutral species via negative ion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, A.

    1991-12-01

    Negative ion photoelectron spectroscopy has been used to study two types of transient neutral species: bound free radicals (NO{sub 2} and NO{sub 3}) and unstable neutral species ([IHI] and [FH{sub 2}]). The negative ion time-of-flight photoelectron spectrometer used for these experiments is described in detail.

  4. Spectroscopy of transient neutral species via negative ion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, A.

    1991-12-01

    Negative ion photoelectron spectroscopy has been used to study two types of transient neutral species: bound free radicals (NO{sub 2} and NO{sub 3}) and unstable neutral species ((IHI) and (FH{sub 2})). The negative ion time-of-flight photoelectron spectrometer used for these experiments is described in detail.

  5. Photoelectron spectroscopy and the dipole approximation

    Energy Technology Data Exchange (ETDEWEB)

    Hemmers, O.; Hansen, D.L.; Wang, H. [Univ. of Nevada, Las Vegas, NV (United States)] [and others

    1997-04-01

    Photoelectron spectroscopy is a powerful technique because it directly probes, via the measurement of photoelectron kinetic energies, orbital and band structure in valence and core levels in a wide variety of samples. The technique becomes even more powerful when it is performed in an angle-resolved mode, where photoelectrons are distinguished not only by their kinetic energy, but by their direction of emission as well. Determining the probability of electron ejection as a function of angle probes the different quantum-mechanical channels available to a photoemission process, because it is sensitive to phase differences among the channels. As a result, angle-resolved photoemission has been used successfully for many years to provide stringent tests of the understanding of basic physical processes underlying gas-phase and solid-state interactions with radiation. One mainstay in the application of angle-resolved photoelectron spectroscopy is the well-known electric-dipole approximation for photon interactions. In this simplification, all higher-order terms, such as those due to electric-quadrupole and magnetic-dipole interactions, are neglected. As the photon energy increases, however, effects beyond the dipole approximation become important. To best determine the range of validity of the dipole approximation, photoemission measurements on a simple atomic system, neon, where extra-atomic effects cannot play a role, were performed at BL 8.0. The measurements show that deviations from {open_quotes}dipole{close_quotes} expectations in angle-resolved valence photoemission are observable for photon energies down to at least 0.25 keV, and are quite significant at energies around 1 keV. From these results, it is clear that non-dipole angular-distribution effects may need to be considered in any application of angle-resolved photoelectron spectroscopy that uses x-ray photons of energies as low as a few hundred eV.

  6. X-Ray photoelectron Spectroscopy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Engelhard, Mark H.; Droubay, Timothy C.; Du, Yingge

    2017-01-03

    With capability for obtaining quantitative elemental composition, chemical and electronic state, and overlayer thickness information from the top ~10 nm of a sample surface, X-ray Photoelectron Spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA) is a versatile and widely used technique for analyzing surfaces. The technique is applied to a host of materials, from insulators to conductors in virtually every scientific field and sub-discipline. More recently, XPS has been extended under in-situ and operando conditions. Following a brief introduction to XPS principles and instrument components, this article exemplifies widely ranging XPS applications in material and life sciences.

  7. Photoelectron spectroscopy bulk and surface electronic structures

    CERN Document Server

    Suga, Shigemasa

    2014-01-01

    Photoelectron spectroscopy is now becoming more and more required to investigate electronic structures of various solid materials in the bulk, on surfaces as well as at buried interfaces. The energy resolution was much improved in the last decade down to 1 meV in the low photon energy region. Now this technique is available from a few eV up to 10 keV by use of lasers, electron cyclotron resonance lamps in addition to synchrotron radiation and X-ray tubes. High resolution angle resolved photoelectron spectroscopy (ARPES) is now widely applied to band mapping of materials. It attracts a wide attention from both fundamental science and material engineering. Studies of the dynamics of excited states are feasible by time of flight spectroscopy with fully utilizing the pulse structures of synchrotron radiation as well as lasers including the free electron lasers (FEL). Spin resolved studies also made dramatic progress by using higher efficiency spin detectors and two dimensional spin detectors. Polarization depend...

  8. Anion photoelectron spectroscopy of radicals and clusters

    Energy Technology Data Exchange (ETDEWEB)

    Travis, Taylor R. [Univ. of California, Berkeley, CA (United States)

    1999-12-01

    Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying 2Σ and 2π states of C2nH (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree of vibronic coupling in C2H and C4H. Other radicals studied include NCN and I3. The author was able to observe the low-lying singlet and triplet states of NCN for the first time. Measurement of the electron affinity of I3 revealed that it has a bound ground state and attachment of an argon atom to this moiety enabled him to resolve the symmetric stretching progression.

  9. Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

    Science.gov (United States)

    Weatherup, Robert S; Eren, Baran; Hao, Yibo; Bluhm, Hendrik; Salmeron, Miquel B

    2016-05-05

    Atmospheric pressure X-ray photoelectron spectroscopy (XPS) is demonstrated using single-layer graphene membranes as photoelectron-transparent barriers that sustain pressure differences in excess of 6 orders of magnitude. The graphene serves as a support for catalyst nanoparticles under atmospheric pressure reaction conditions (up to 1.5 bar), where XPS allows the oxidation state of Cu nanoparticles and gas phase species to be simultaneously probed. We thereby observe that the Cu(2+) oxidation state is stable in O2 (1 bar) but is spontaneously reduced under vacuum. We further demonstrate the detection of various gas-phase species (Ar, CO, CO2, N2, O2) in the pressure range 10-1500 mbar including species with low photoionization cross sections (He, H2). Pressure-dependent changes in the apparent binding energies of gas-phase species are observed, attributable to changes in work function of the metal-coated grids supporting the graphene. We expect atmospheric pressure XPS based on this graphene membrane approach to be a valuable tool for studying nanoparticle catalysis.

  10. X-ray Photoelectron Spectroscopy Database (Version 4.1)

    Science.gov (United States)

    SRD 20 X-ray Photoelectron Spectroscopy Database (Version 4.1) (Web, free access)   The NIST XPS Database gives access to energies of many photoelectron and Auger-electron spectral lines. The database contains over 22,000 line positions, chemical shifts, doublet splittings, and energy separations of photoelectron and Auger-electron lines.

  11. Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

    Energy Technology Data Exchange (ETDEWEB)

    Bradforth, S.E.

    1992-11-01

    The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound [yields] bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN[sup [minus

  12. Attosecond electronic and nuclear quantum photodynamics of ozone monitored with time and angle resolved photoelectron spectra

    CERN Document Server

    Decleva, P; Perveaux, A; Lauvergnat, D; Gatti, F; Lasorne, B; Halász, G J; Vibók, Á

    2016-01-01

    Recently we reported a series of numerical simulations proving that it is possible in principle to create an electronic wave packet and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds. We considered the ozone molecule: for this system the electronic wave packet leads to a dissociation process. In the present work, we investigate more specifically the time-resolved photoelectron angular distribution of the ozone molecule that provides a much more detailed description of the evolution of the electronic wave packet. We thus show that this experimental technique should be able to give access to observing in real time the creation of an electronic wave packet in a neutral molecule and its impact on a chemical process.

  13. Attosecond electronic and nuclear quantum photodynamics of ozone monitored with time and angle resolved photoelectron spectra

    Science.gov (United States)

    Decleva, Piero; Quadri, Nicola; Perveaux, Aurelie; Lauvergnat, David; Gatti, Fabien; Lasorne, Benjamin; Halász, Gábor J.; Vibók, Ágnes

    2016-11-01

    Recently we reported a series of numerical simulations proving that it is possible in principle to create an electronic wave packet and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds. We considered the ozone molecule: for this system the electronic wave packet leads to a dissociation process. In the present work, we investigate more specifically the time-resolved photoelectron angular distribution of the ozone molecule that provides a much more detailed description of the evolution of the electronic wave packet. We thus show that this experimental technique should be able to give access to observing in real time the creation of an electronic wave packet in a neutral molecule and its impact on a chemical process.

  14. Photoelectron spectroscopy of strongly correlated Yb compounds

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.J.; Andrews, A.B.; Arko, A.J.; Bartlett, R.J.; Blythe, R.I. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Olson, C.G.; Benning, P.J.; Canfield, P.C. [Ames Laboratory, U. S. Department of Energy, Ames, Iowa 50011 (United States); Poirier, D.M. [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    1996-12-01

    The electronic properties of the Yb compounds YBCu{sub 2}Si{sub 2}, YBAgCu{sub 4}, and YbAl{sub 3} along with purely divalent Yb metal, have been investigated by means of high-resolution ultraviolet and x-ray photoelectron spectroscopy. We present the intrinsic characteristic features of the 4{ital f} levels of Yb while accounting for lattice vibrations and the manifestation of corelike energy levels degenerate with the valence states and modified by the temperature-dependent Fermi function. For these strongly correlated Yb-based compounds, the hole occupancy values ({ital n}{sub {ital f}}{approximately}0.6) directly obtained from integration of the divalent and trivalent portions of the 4{ital f} photoemission features indicate that these compounds are strongly mixed valent. The small intensity modulation with temperature in the divalent Yb 4{ital f} levels (0{endash}10{percent} over a {ital T}=20{minus}300 K range) is discussed within the conventional framework of the photoemission process and nominal allowances for lattice variations with temperature. Results from photoemission experiments on the divalent 4{ital f} levels of strongly correlated Yb compounds are remarkably similar to the 4{ital f} levels of purely divalent Yb metal. {copyright} {ital 1996 The American Physical Society.}

  15. Threshold photoelectron spectroscopy of the imidogen radical

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Gustavo A., E-mail: gustavo.garcia@synchrotron-soleil.fr [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette (France); Gans, Bérenger [Institut des Sciences Moléculaires d’Orsay, Univ Paris-Sud, CNRS, Bât 210, Univ Paris-Sud, 91405 Orsay Cedex (France); Tang, Xiaofeng [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette (France); Ward, Michael; Batut, Sébastien [PC2A, Université de Lille 1, UMR CNRS-USTL 8522, Cité Scientifique Bât. C11, F-59655 Villeneuve d’Ascq (France); Nahon, Laurent [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette (France); Fittschen, Christa [PC2A, Université de Lille 1, UMR CNRS-USTL 8522, Cité Scientifique Bât. C11, F-59655 Villeneuve d’Ascq (France); Loison, Jean-Christophe [ISM, Université de Bordeaux, CNRS, 351 cours de la Libération, 33405 Talence Cedex (France)

    2015-08-15

    We present the threshold photoelectron spectroscopy of the imidogen radical (NH) recorded in the photon energy region up to 1 eV above its first ionization threshold. The radical was produced by reaction of NH{sub 3} and F in a microwave discharge flow-tube and photoionized using vacuum ultraviolet (VUV) synchrotron radiation. A double imaging coincidence spectrometer was used to record mass-selected spectra and avoid contributions from the byproducts present in the reactor and background gas. The energy region includes the ground X{sup +2}Π and first electronically excited a{sup +4}Σ{sup −} states of NH{sup +}. Strong adiabatic transitions and weak vibrational progressions up to v{sup +} = 2 are observed for both electronic states. The rotational profile seen in the origin band has been modeled using existing neutral and cationic spectroscopic constants leading to a precise determination of the adiabatic ionization energy at 13.480 ± 0.002 eV.

  16. Photoelectron spectroscopy and Auger electron spectroscopy of solids and surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kowalczyk, S.P.

    1976-01-01

    The use of photoelectron spectroscopy, primarily x-ray photoelectron spectroscopy, to obtain information on the electronic structure of a wide variety of solids (especially the bulk electronic structure of solids) is covered. Both valence band and core-level spectra, as well as a few cases of photon excited Auger electron spectroscopy, are employed in the investigations to derive information on N(E). The effect of several modulations inherent in the measured I(E)'s, such as final state band structure, cross section, and relaxation, is discussed. Examples of many-electron interactions in PES are given. Some experimental aspects of PES and AES studies are given with emphasis on sample preparation techniques. Multiple splitting of core levels is examined using the Mn levels in MnF/sub 2/ as a detailed case study. Core level splittings in transition metals, rare earth metals, transition metal halides and several alloys are also reported. The application of PES to the study of the chemical bond in some crystalline semiconductors and insulators, A/sup N/B/sup 8-N/ and A/sup N/B/sup 10-N/ compounds is treated, and a spectroscopic scale of ionicity for these compounds is developed from the measured ''s-band'' splitting in the valence band density of states. (GHT)

  17. Attosecond Lighthouses

    CERN Document Server

    Vincenti, H

    2011-01-01

    Coherent light beams composed of ultrashort pulses are now increasingly used in different fields of Science, from time-resolved spectroscopy to plasma physics. Under the effect of even simple optical components, the spatial properties of these beams can vary over the duration of the light pulse. In this letter, we show how such spatio-temporally coupled electromagnetic fields can be exploited to produce an attosecond lighthouse, i.e. a source emitting a collection of isolated attosecond pulses, propagating in angularly well-separated light beams. This very general effect not only opens the way to a new generation of attosecond light sources, particularly suitable for pump-probe experiments, but also provides a powerful new tool for ultrafast metrology, for instance giving direct access to fluctuations in the phase of the laser field oscillations with respect to the pulse envelop, right at the focus of even the most intense ultrashort laser beams.

  18. Anion photoelectron imaging spectroscopy of glyoxal

    Science.gov (United States)

    Xue, Tian; Dixon, Andrew R.; Sanov, Andrei

    2016-09-01

    We report a photoelectron imaging study of the radical-anion of glyoxal. The 532 nm photoelectron spectrum provides the first direct spectroscopic determination of the adiabatic electron affinity of glyoxal, EA = 1.10 ± 0.02 eV. This assignment is supported by a Franck-Condon simulation of the experimental spectrum that successfully reproduces the observed spectral features. The vertical detachment energy of the radical-anion is determined as VDE = 1.30 ± 0.04 eV. The reported EA and VDE values are attributed to the most stable (C2h symmetry) isomers of the neutral and the anion.

  19. Threshold photoelectron spectroscopy of acetaldehyde and acrolein

    Energy Technology Data Exchange (ETDEWEB)

    Yencha, Andrew J., E-mail: ayencha@albany.edu [Department of Chemistry, University at Albany, State University of New York, Albany, NY 12222 (United States); Siggel-King, Michele R.F. [Cockcroft Institute, Sci-Tech Daresbury, Warrrington WA4 4AD (United Kingdom); Department of Physics, University of Liverpool, Liverpool L69 3BX (United Kingdom); King, George C. [Department of Physics and Astronomy and Photon Science Institute, Manchester University, Manchester M13 9PL (United Kingdom); Malins, Andrew E.R. [Cockcroft Institute, Sci-Tech Daresbury, Warrrington WA4 4AD (United Kingdom); Eypper, Marie [School of Chemistry, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2013-04-15

    Highlights: •High-resolution threshold photoelectron spectrum of acetaldehyde. •High-resolution threshold photoelectron spectrum of acrolein. •High-resolution total photoion yield spectrum of acetaldehyde. •High-resolution total photoion yield spectrum of acrolein. •Determination of vertical ionization potentials in acetaldehyde and acrolein. -- Abstract: High-resolution (6 meV and 12 meV) threshold photoelectron (TPE) spectra of acetaldehyde and acrolein (2-propenal) have been recorded over the valence binding energy region 10–20 eV, employing synchrotron radiation and a penetrating-field electron spectrometer. These TPE spectra are presented here for the first time. All of the band structures observed in the TPE spectra replicate those found in their conventional HeI photoelectron (PE) spectra. However, the relative band intensities are found to be dramatically different in the two types of spectra that are attributed to the different dominant operative formation mechanisms. In addition, some band shapes and their vertical ionization potentials are found to differ in the two types of spectra that are associated with the autoionization of Rydberg states in the two molecules.

  20. Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

    Energy Technology Data Exchange (ETDEWEB)

    Bradforth, S.E.

    1992-11-01

    The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound {yields} bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN{sup {minus}}, NCO{sup {minus}} and NCS{sup {minus}}. Transition state photoelectron spectra are presented for the following systems Br + HI, Cl + HI, F + HI, F + CH{sub 3}0H,F + C{sub 2}H{sub 5}OH,F + OH and F + H{sub 2}. A time dependent framework for the simulation and interpretation of the bound {yields} free transition state photoelectron spectra is subsequently developed and applied to the hydrogen transfer reactions Br + HI, F + OH {yields} O({sup 3}P, {sup 1}D) + HF and F + H{sub 2}. The theoretical approach for the simulations is a fully quantum-mechanical wave packet propagation on a collinear model reaction potential surface. The connection between the wavepacket time evolution and the photoelectron spectrum is given by the time autocorrelation function. For the benchmark F + H{sub 2} system, comparisons with three-dimensional quantum calculations are made.

  1. Surface Reactions Studied by Synchrotron Based Photoelectron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hrbek, J.

    1998-11-03

    The goal of this article is to illustrate the use of synchrotron radiation for investigating surface chemical reactions by photoelectron spectroscopy. A brief introduction and background information is followed by examples of layer resolved spectroscopy, oxidation and sulfidation of metallic, semiconducting and oxide surfaces.

  2. AXSIS: Exploring the frontiers in attosecond X-ray science, imaging and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kärtner, F.X., E-mail: franz.kaertner@cfel.de [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA (United States); Ahr, F. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); DESY, Hamburg (Germany); Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Calendron, A.-L. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Çankaya, H. [Center for Free-Electron Laser Science, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Carbajo, S. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); DESY, Hamburg (Germany); Chang, G.; Cirmi, G. [Center for Free-Electron Laser Science, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Dörner, K. [Center for Free-Electron Laser Science, Hamburg (Germany); DESY, Hamburg (Germany); Dorda, U. [DESY, Hamburg (Germany); Fallahi, A. [Center for Free-Electron Laser Science, Hamburg (Germany); DESY, Hamburg (Germany); Hartin, A. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); DESY, Hamburg (Germany); Hemmer, M. [Center for Free-Electron Laser Science, Hamburg (Germany); DESY, Hamburg (Germany); and others

    2016-09-01

    X-ray crystallography is one of the main methods to determine atomic-resolution 3D images of the whole spectrum of molecules ranging from small inorganic clusters to large protein complexes consisting of hundred-thousands of atoms that constitute the macromolecular machinery of life. Life is not static, and unravelling the structure and dynamics of the most important reactions in chemistry and biology is essential to uncover their mechanism. Many of these reactions, including photosynthesis which drives our biosphere, are light induced and occur on ultrafast timescales. These have been studied with high time resolution primarily by optical spectroscopy, enabled by ultrafast laser technology, but they reduce the vast complexity of the process to a few reaction coordinates. In the AXSIS project at CFEL in Hamburg, funded by the European Research Council, we develop the new method of attosecond serial X-ray crystallography and spectroscopy, to give a full description of ultrafast processes atomically resolved in real space and on the electronic energy landscape, from co-measurement of X-ray and optical spectra, and X-ray diffraction. This technique will revolutionize our understanding of structure and function at the atomic and molecular level and thereby unravel fundamental processes in chemistry and biology like energy conversion processes. For that purpose, we develop a compact, fully coherent, THz-driven attosecond X-ray source based on coherent inverse Compton scattering off a free-electron crystal, to outrun radiation damage effects due to the necessary high X-ray irradiance required to acquire diffraction signals. This highly synergistic project starts from a completely clean slate rather than conforming to the specifications of a large free-electron laser (FEL) user facility, to optimize the entire instrumentation towards fundamental measurements of the mechanism of light absorption and excitation energy transfer. A multidisciplinary team formed by laser

  3. Photoelectron spectroscopy in heavy fermions: Inconsistencies with the Kondo model

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.; Joyce, J.J.; Blyth, R.R.; Canfield, P.C.; Thompson, J.D.; Bartlett, R.J.; Fisk, Z. [Los Alamos National Lab., NM (United States); Lawrence, J.; Tang, J. [California Univ., Irvine, CA (United States); Riseborough, P. [Polytechnic Univ., Brooklyn, NY (United States)

    1992-09-01

    We have investigated a number of Ce and Yb heavy fermion compounds via photoelectron spectroscopy and compared the results to the predictions of the Imurity Anderson Hamiltonian within the Gunnarson-Schonhammer approach. For the low T{sub K} materials investigated we find little or no correlation with T{sub K}, the only parameter that can be determined independent of photoemission.

  4. Characterization of Ge-nanocrystal films with photoelectron spectroscopy

    CERN Document Server

    Bostedt, C; Willey, T M; Nelson, A J; Franco, N; Möller, T; Terminello, L J

    2003-01-01

    The Ge 3d core-levels of germanium nanocrystal films have been investigated by means of photoelectron spectroscopy. The experiments indicate bulk-like coordinated atoms in the nanocrystals and suggest structured disorder on the nanoparticle surface. The results underline the importance of the surface on the overall electronic structure of this class of nanostructured materials.

  5. Flexible attosecond beamline for high harmonic spectroscopy and XUV/near-IR pump probe experiments requiring long acquisition times

    Energy Technology Data Exchange (ETDEWEB)

    Weber, S. J., E-mail: sebastien.weber@cea.fr; Manschwetus, B.; Billon, M.; Bougeard, M.; Breger, P.; Géléoc, M.; Gruson, V.; Lin, N.; Ruchon, T.; Salières, P.; Carré, B. [Commissariat l’Energie Atomique, Laser, Interactions and Dynamics Laboratory (LIDyL), DSM/IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Böttcher, M.; Huetz, A.; Picard, Y. J. [ISMO, UMR 8214, Université Paris-Sud, Batiment 350, Orsay (France)

    2015-03-15

    We describe the versatile features of the attosecond beamline recently installed at CEA-Saclay on the PLFA kHz laser. It combines a fine and very complete set of diagnostics enabling high harmonic spectroscopy (HHS) through the advanced characterization of the amplitude, phase, and polarization of the harmonic emission. It also allows a variety of photo-ionization experiments using magnetic bottle and COLTRIMS (COLd Target Recoil Ion Momentum Microscopy) electron spectrometers that may be used simultaneously, thanks to a two-foci configuration. Using both passive and active stabilization, special care was paid to the long term stability of the system to allow, using both experimental approaches, time resolved studies with attosecond precision, typically over several hours of acquisition times. As an illustration, applications to multi-orbital HHS and electron-ion coincidence time resolved spectroscopy are presented.

  6. Angular distribution and atomic effects in condensed phase photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Davis, R.F.

    1981-11-01

    A general concept of condensed phase photoelectron spectroscopy is that angular distribution and atomic effects in the photoemission intensity are determined by different mechanisms, the former being determined largely by ordering phenomena such as crystal momentum conservation and photoelectron diffraction while the latter are manifested in the total (angle-integrated) cross section. In this work, the physics of the photoemission process is investigated in several very different experiments to elucidate the mechanisms of, and correlation between, atomic and angular distribution effects. Theoretical models are discussed and the connection betweeen the two effects is clearly established. The remainder of this thesis, which describes experiments utilizing both angle-resolved and angle-integrated photoemission in conjunction with synchrotron radiation in the energy range 6 eV less than or equal to h ..nu.. less than or equal to 360 eV and laboratory sources, is divided into three parts.

  7. Hard X-ray photoelectron spectroscopy: A few recent applications

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, M., E-mail: mtaguchi@spring8.or.jp [RIKEN SPring-8 Center, Sayo, Hyogo 679-5148 (Japan); Takata, Y.; Chainani, A. [RIKEN SPring-8 Center, Sayo, Hyogo 679-5148 (Japan)

    2013-10-15

    Highlights: ► We discuss recent applications of HAXPES carried out at BL29XU in SPring-8. ► We provide a brief description of the salient features of the instrument. ► The recoil effect of photoelectrons in core levels and valence band are discussed. ► We overview HAXPES studies of a series of 3d transition metal compounds. ► The extended cluster model for explaining well-screened feature is presented. -- Abstract: In this report, we discuss a few recent applications of hard X-ray photoelectron spectroscopy (HAXPES) carried out at the RIKEN beamline BL29XU in SPring-8. We first provide a brief description of the salient features of the instrument in operation at BL29 XU in SPring-8. HAXPES studies on the recoil effect of photoelectrons in core levels and valence band states are presented. The experiments show remarkable consistency with theoretical results and indicate the role of phonon excitations in the recoil effect of photoelectrons. We then overview HAXPES applied to the study of a series of 3d transition metal (TM) compounds. The HAXPES experimental results often show an additional well-screened feature in bulk sensitive electronic structure of strongly correlated compounds compared to surface sensitive spectra. The extended cluster model developed by us for explaining this well-screened feature is validated for a series of TM compounds. These results show that HAXPES is a valuable tool for the study of doping and temperature dependent electronic structure of solids with tremendous potential for future activities.

  8. Ambient pressure photoelectron spectroscopy: Practical considerations and experimental frontiers

    Science.gov (United States)

    Trotochaud, Lena; Head, Ashley R.; Karslıoğlu, Osman; Kyhl, Line; Bluhm, Hendrik

    2017-02-01

    Over the past several decades, ambient pressure x-ray photoelectron spectroscopy (APXPS) has emerged as a powerful technique for in situ and operando investigations of chemical reactions under relevant ambient atmospheres far from ultra-high vacuum conditions. This review focuses on exemplary cases of APXPS experiments, giving special consideration to experimental techniques, challenges, and limitations specific to distinct condensed matter interfaces. We discuss APXPS experiments on solid/vapor interfaces, including the special case of 2D films of graphene and hexagonal boron nitride on metal substrates with intercalated gas molecules, liquid/vapor interfaces, and liquid/solid interfaces, which are a relatively new class of interfaces being probed by APXPS. We also provide a critical evaluation of the persistent limitations and challenges of APXPS, as well as the current experimental frontiers.

  9. SPIN POLARIZED PHOTOELECTRON SPECTROSCOPY AS A PROBE OF MAGNETIC SYSTEMS.

    Energy Technology Data Exchange (ETDEWEB)

    JOHNSON, P.D.; GUNTHERODT, G.

    2006-11-01

    Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.

  10. Nuclear-Motion Effects in Attosecond Transient Absorption Spectroscopy of Molecules

    CERN Document Server

    Bækhøj, Jens E; Madsen, Lars Bojer

    2015-01-01

    We investigate the characteristic effects of nuclear motion on attosecond transient absorption spectra in molecules by calculating the spectrum for different model systems. Two models of the hydrogen molecular ion are considered: one where the internuclear separation is fixed, and one where the nuclei are free to vibrate. The spectra for the fixed nuclei model are similar to atomic spectra reported elsewhere, while the spectra obtained in the model including nuclear motion are very different and dominated by extremely broad absorption features. These broad absorption features are analyzed and their relation to molecular dissociation investigated. The study of the hydrogen molecular ion validates an approach based on the Born-Oppenheimer approximation and a finite electronic basis. This latter approach is then used to study the three-dimensional hydrogen molecule including nuclear vibration. The spectrum obtained from H$_2$ is compared to the result of a fixed-nuclei calculation. In the attosecond transient ab...

  11. Towards attosecond measurement in molecules and at surfaces

    Science.gov (United States)

    Marangos, Jonathan

    2015-05-01

    1) We will present a number of experimental approaches that are being developed at Imperial College to make attosecond timescale measurements of electronic dynamics in suddenly photoionized molecules and at surfaces. A brief overview will be given of some of the unanswered questions in ultrafast electron and hole dynamics in molecules and solids. These questions include the existence of electronic charge migration in molecules and how this process might couple to nuclear motion even on the few femtosecond timescale. How the timescale of photoemission from a surface may differ from that of an isolated atom, e.g. due to electron transport phenomena associated with the distance from the surface of the emitting atom and the electron dispersion relation, is also an open question. 2) The measurement techniques we are currently developing to answer these questions are HHG spectroscopy, attosecond pump-probe photoelectron/photoion studies, and attosecond pump-probe transient absorption as well as attosecond streaking for measuring surface emission. We will present recent advances in generating two synchronized isolated attosecond pulses at different colours for pump-probe measurements (at 20 eV and 90 eV respectively). Results on generation of isolated attosecond pulses at 300 eV and higher photon energy using a few-cycle 1800 nm OPG source will be presented. The use of these resources for making pump-probe measurements will be discussed. Finally we will present the results of streaking measurement of photoemission wavepackets from two types of surface (WO3 and a evaporated Au film) that show a temporal broadening of ~ 100 as compared to atomic streaks that is consistent with the electron mean free path in these materials. Work supported by ERC and EPSRC.

  12. Alignment of the photoelectron spectroscopy beamline at NSRL

    CERN Document Server

    Li, Chaoyang; Wen, Shen; Pan, Congyuan; An, Ning; Du, Xuewei; Zhu, Junfa; Wang, Qiuping

    2013-01-01

    The photoelectron spectroscopy beamline at National Synchrotron Radiation Laboratory (NSRL) is equipped with a spherical grating monochromator with the included angle of 174 deg. Three gratings with line density of 200, 700 and 1200 lines/mm are used to cover the energy region from 60 eV to 1000 eV. After several years operation, the spectral resolution and flux throughput were deteriorated, realignment is necessary to improve the performance. First, the wavelength scanning mechanism, the optical components position and the exit slit guide direction are aligned according to the design value. Second, the gratings are checked by Atomic Force Microscopy (AFM). And then the gas absorption spectrum is measured to optimize the focusing condition of the monochromator. The spectral resolving power is recovered to the designed value of 1000@244eV. The flux at the end station for the 200 lines/mm grating is about 10^10 photons/sec/200mA, which is in accordance with the design. The photon flux for the 700 lines/mm grati...

  13. Insights into electrochemical reactions from ambient pressure photoelectron spectroscopy.

    Science.gov (United States)

    Stoerzinger, Kelsey A; Hong, Wesley T; Crumlin, Ethan J; Bluhm, Hendrik; Shao-Horn, Yang

    2015-11-17

    The understanding of fundamental processes in the bulk and at the interfaces of electrochemical devices is a prerequisite for the development of new technologies with higher efficiency and improved performance. One energy storage scheme of great interest is splitting water to form hydrogen and oxygen gas and converting back to electrical energy by their subsequent recombination with only water as a byproduct. However, kinetic limitations to the rate of oxygen-based electrochemical reactions hamper the efficiency in technologies such as solar fuels, fuel cells, and electrolyzers. For these reactions, the use of metal oxides as electrocatalysts is prevalent due to their stability, low cost, and ability to store oxygen within the lattice. However, due to the inherently convoluted nature of electrochemical and chemical processes in electrochemical systems, it is difficult to isolate and study individual electrochemical processes in a complex system. Therefore, in situ characterization tools are required for observing related physical and chemical processes directly at the places where and while they occur and can help elucidate the mechanisms of charge separation and charge transfer at electrochemical interfaces. X-ray photoelectron spectroscopy (XPS), also known as ESCA (electron spectroscopy for chemical analysis), has been used as a quantitative spectroscopic technique that measures the elemental composition, as well as chemical and electronic state of a material. Building from extensive ex situ characterization of electrochemical systems, initial in situ studies were conducted at or near ultrahigh vacuum (UHV) conditions (≤10(-6) Torr) to probe solid-state electrochemical systems. However, through the integration of differential-pumping stages, XPS can now operate at pressures in the torr range, comprising a technique called ambient pressure XPS (AP-XPS). In this Account, we briefly review the working principles and current status of AP-XPS. We use several recent

  14. Comments on photoelectron spectroscopy of high- Tc 's

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.

    1991-01-01

    The photoemission discussion session during the Argonne conference on Fermiology of High-{Tc}'s provided a forum to air a number of unresolved issues in photoelectron spectroscopy. These are: (a) what is the exact energy dependence of the line width of the quasiparticle peaks: (b) are there any chemical potential shifts with hole doping; (c) why is a superconducting gap not observed in Y-123; and (d) different groups report different results in the band structure of Bi-2212. The first issue, while much discussed, essentially becomes a non-issue in the sense that nearly all theories predict a linear as well as a quadratic energy dependence to the quasiparticle lifetime. Furthermore, the data are not yet good enough to distinguish between linear and quadratic dependence in the important region within 0.1 eV of E{sub F}. Regarding chemical potential shifts, they very definitely are observed with hole doping both in Y-123 and Bi-2212 in spite of the claims by RVB enthusiasts to the contrary. In Y-123 the shifts are as large as 0.75 eV. The non-observation of a gap in Y-123 is puzzling, but may be related to surface reconstruction and an overdoped situation. The important question of whether we have one or two bands near E{sub F} in Bi-2212 revolves around the surface quality of the samples studied by different groups. It is difficult to compare data taken at room temperature vs. data taken at low temperature when no documentation exists that a reconstruction did not occur. We suspect that the small second band championed by the Sendai group is a surface impurity band.

  15. Coincident photoelectron spectroscopy on superconductors; Koinzidente Photoelektronenspektroskopie an Supraleitern

    Energy Technology Data Exchange (ETDEWEB)

    Voss, Stefan

    2011-07-01

    Aim of the performed experiments of this thesis was to attempt to detect Cooper pairs as carriers of the superconducting current directly by means of the photoelectric effect. The method of the coincident photoelectron spectroscopy aims thereby at the detection of two coherently emitted electrons by the interaction with a photon. Because electrostatic analyzers typically cover only a very small spatial angle, which goes along with very low coincidence rates, in connection with this thesis a time-of-flight projection system has been developed, which maps nearly the whole spatial angle on a position-resolving detector. The pulsed light source in form of special synchrotron radiation necessary for the measurement has been adjusted so weak, that only single photons could arrive at the sample. Spectroscoped were beside test measurements on silver layers both a lead monocrystal as representative of the classical BCS superconductors and monocrystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} from the family of the high-temperature superconductors. With excitation energies up to 40 eV could be shown that sufficiently smooth and clean surfaces in the superconducting phase exhibit within the resolving power of about 0.5 eV no recognizable differences in comparison to the normally conducting phase. Beside these studies furthermore the simple photoemission at the different samples and especially in the case of the lead crystal is treated, because here no comparable results are known. Thereby the whole momentum space is discussed and the Fermi surface established as three-dimensional model, by means of which the measurement results are discussed. in the theoretical descriptions different models for the Cooper-pair production are presented, whereby to the momentum exchange with the crystal a special role is attributed, because this can only occur in direct excitations via discrete lattice vectors.

  16. The Electron-Phonon Interaction as Studied by Photoelectron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    D.W. Lynch

    2004-09-30

    With recent advances in energy and angle resolution, the effects of electron-phonon interactions are manifest in many valence-band photoelectron spectra (PES) for states near the Fermi level in metals.

  17. Time-resolved photoelectron spectroscopy of non-adiabatic dynamics in polyatomic molecules

    CERN Document Server

    Stolow, Albert

    2015-01-01

    This review article discusses advances in the use of time-resolved photoelectron spectroscopy for the study of non-adiabatic processes in molecules. A theoretical treatment of the experiments is presented together with a number of experimental examples.

  18. Time-resolved photoelectron spectroscopy and ab initio multiple spawning studies of hexamethylcyclopentadiene

    DEFF Research Database (Denmark)

    Wolf, T. J. A.; Kuhlman, Thomas Scheby; Schalk, O.

    2014-01-01

    Time-resolved photoelectron spectroscopy and ab initio multiple spawning were applied to the ultrafast non-adiabatic dynamics of hexamethylcyclopentadiene. The high level of agreement between experiment and theory associates wavepacket motion with a distinct degree of freedom....

  19. Photoelectron spectroscopy on doped organic semiconductors and related interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Olthof, Selina Sandra

    2010-06-08

    Using photoelectron spectroscopy, we show measurements of energy level alignment of organic semiconducting layers. The main focus is on the properties and the influence of doped layers. The investigations on the p-doping process in organic semiconductors show typical charge carrier concentrations up to 2.10{sup 20} cm{sup -3}. By a variation of the doping concentration, an over proportional influence on the position of the Fermi energy is observed. Comparing the number of charge carriers with the amount of dopants present in the layer, it is found that only 5% of the dopants undergo a full charge transfer. Furthermore, a detailed investigation of the density of states beyond the HOMO onset reveals that an exponentially decaying density of states reaches further into the band gap than commonly assumed. For an increasing amount of doping, the Fermi energy gets pinned on these states which suggests that a significant amount of charge carriers is present there. The investigation of metal top and bottom contacts aims at understanding the asymmetric current-voltage characteristics found for some symmetrically built device stacks. It can be shown that a reaction between the atoms from the top contact with the molecules of the layer leads to a change in energy level alignment that produces a 1.16 eV lower electron injection barrier from the top. Further detailed investigations on such contacts show that the formation of a silver top contact is dominated by diffusion processes, leading to a broadened interface. However, upon insertion of a thin aluminum interlayer this diffusion can be stopped and an abrupt interface is achieved. Furthermore, in the case of a thick silver top contact, a monolayer of molecules is found to oat on top of the metal layer, almost independent on the metal layer thickness. Finally, several device stacks are investigated, regarding interface dipoles, formation of depletion regions, energy alignment in mixed layers, and the influence of the built

  20. Real-time analysis for MBE by time-resolved core-level photoelectron spectroscopy.

    Science.gov (United States)

    Maeda, F; Watanabe, Y; Oshima, M; Taguchi, M; Oiwa, R

    1998-05-01

    A system has been developed for the real-time analysis of surface reactions during molecular beam epitaxial growth which uses photoelectron spectroscopy with VUV light taken from synchrotron radiation. This system consists of a synchrotron radiation beamline and growth/analysis apparatus in which photoelectron spectroscopy is performed with sub-second time resolution. In this system, photoelectron spectra are measured in sequence by a 'non-scanning' measurement method that enables the acquisition of snapshot photoelectron spectra using a multi-channel detector. This non-scanning measurement method was enabled by equipping an electric field correction grid. This system was used to monitor the photoelectron spectra of a GaSb(001) surface.

  1. Assignment of benzodiazepine UV absorption spectra by the use of photoelectron spectroscopy

    Science.gov (United States)

    Khvostenko, O. G.; Tzeplin, E. E.; Lomakin, G. S.

    2002-04-01

    Correlations between singlet transition energies and energy gaps of corresponding pairs of occupied and unoccupied molecular orbitals were revealed in a series of benzodiazepines. The occupied orbital energies were taken from the photoelectron spectra of the compound investigated, the unoccupied ones were obtained from MNDO/d calculations, and the singlet energies were taken from the UV absorption spectra. The correspondence of the singlet transitions to certain molecular orbitals was established using MNDO/d calculations and comparing between UV and photoelectron spectra. It has been concluded that photoelectron spectroscopy can be applied for interpretation of UV absorption spectra of various compounds on the basis of similar correlations.

  2. Photoelectron Spectroscopy,Photoionization Mass Spectroscopy,and Theoretical Study on CCI3SSCN

    Institute of Scientific and Technical Information of China (English)

    Lin Du; Li Yao; Mao-fa Ge

    2008-01-01

    Trichloromethanesulfenyl thiocyanate,CCI3SSCN,was generated and studied by photoelectron spectroscoy (PES),photoionization mass spectroscopy(PIMS),and theoretical calculations.This molecule exhibits a gaucho conformation,and the torsional angle around S-S bond is 91.4° due to the sulfur-sulfur lone pair interactions.After ionization,the ground-state cationic-radical form of CC13SSCN+ adopts a trans planar main-atom structure with Cs symmetry.The highest occupied molecular orbital (HOMO) of CCI3SSCN corresponds to the electrons mainly localized on the sulfur 3p lone pair MO.The first ionization energy is determined to be 10.40 eV.

  3. Multiphoton ionization photoelectron spectroscopy of xenon: Experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Bajic, S.J.; Compton, R.N.; Tang, X.; L' Huiller, A.; Lambropoulos, P.

    1988-11-01

    Photoelectron energy and angular distributions for resonantly enhanced multiphoton ionization (REMPI) of xenon via the three-photon-allowed 7s(3/2)/sub 1//sup 0/ and 5d(3/2)/sub 1//sup 0/ states have been studied both experimentally and theoretically. The electron kinetic energy spectra give the probability of leaving Xe/sup +/ in either the /sup 2/P/sub 1/2/ or /sup 2/P/sub 3/2/ core. The measured branching ratio for leaving each ionic core is used to test the theoretical description of the REMPI process. Measurements of both the angular distributions and the (3+1) REMPI via the 5d state are adequately reproduced by multichannel quantum defect theory. However, measurements of angular distributions for the electrons resulting from (3+1) via the 7s(3/2)/sub 1//sup 0/ state into Xe/sup +/ /sup 2/P/sub 3/2/ (core preserving) or Xe/sup +/ /sup 2/P/sub 1/2/ (core changing) are in striking disagreement with theory. 1 ref., 2 figs.

  4. FORTRAN program for x ray photoelectron spectroscopy data reformatting

    Science.gov (United States)

    Abel, Phillip B.

    1989-01-01

    A FORTRAN program has been written for use on an IBM PC/XT or AT or compatible microcomputer (personal computer, PC) that converts a column of ASCII-format numbers into a binary-format file suitable for interactive analysis on a Digital Equipment Corporation (DEC) computer running the VGS-5000 Enhanced Data Processing (EDP) software package. The incompatible floating-point number representations of the two computers were compared, and a subroutine was created to correctly store floating-point numbers on the IBM PC, which can be directly read by the DEC computer. Any file transfer protocol having provision for binary data can be used to transmit the resulting file from the PC to the DEC machine. The data file header required by the EDP programs for an x ray photoelectron spectrum is also written to the file. The user is prompted for the relevant experimental parameters, which are then properly coded into the format used internally by all of the VGS-5000 series EDP packages.

  5. Characterization of EUV irradiation effects on polystyrene derivatives studied by x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS)

    Science.gov (United States)

    Yamamoto, Hiroki; Kozawa, Takahiro; Tagawa, Seiichi

    2011-04-01

    The trade-off among resolution, sensitivity, and line edge roughness (LER) is the most serious problem in actualization of extreme ultraviolet (EUV). As feature sizes are reduced, it becomes very strict to simultaneously meet these requirements. Also, reaction in resist materials induced by EUV photon is more complicate. In chemically amplified EUV resists, not acid generator but polymers mainly adsorbed EUV photons. The secondary electrons are generated from polymer upon exposure to ionizing radiation such as EUV radiation and electron beam. Therefore, the increase in secondary electrons generated by EUV photons adsorbed in resist film is very important factor in the resist design. Therefore, it is essential to know the ionization mechanisms of backbone polymers and understand the reaction mechanism in details in order to accomplish high sensitivity and ultra-fine pattern in EUV lithography. We investigated the photoelectron spectra of typical backbone polymers for chemically amplified EUV resists using ultraviolet photoelectron spectroscopy (UPS). Also, the structure degradations in polystyrene (PS) derivatives thin films induced by EUV radiation were analyzed by X-ray photoelectron spectroscopy (XPS) and UPS.

  6. Photoelectron Spectroscopy under Ambient Pressure and Temperature Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ogletree, D. Frank; Bluhm, Hendrik; Hebenstreit, Eleonore B.; Salmeron, Miquel

    2009-02-27

    We describe the development and applications of novel instrumentation for photoemission spectroscopy of solid or liquid surfaces in the presence of gases under ambient conditions or pressure and temperature. The new instrument overcomes the strong scattering of electrons in gases by the use of an aperture close to the surface followed by a differentially-pumped electrostatic lens system. In addition to the scattering problem, experiments in the presence of condensed water or other liquids require the development of special sample holders to provide localized cooling. We discuss the first two generations of Ambient Pressure PhotoEmission Spectroscopy (APPES) instruments developed at synchrotron light sources (ALS in Berkeley and BESSY in Berlin), with special focus on the Berkeley instruments. Applications to environmental science and catalytic chemical research are illustrated in two examples.

  7. X-ray photoelectron spectroscopy for the study of microbial cell surfaces

    NARCIS (Netherlands)

    van der Mei, Henderina C; de Vries, Jacob; Busscher, Hendrik J

    2000-01-01

    X-ray photoelectron spectroscopy (XPS) is well known for the characterisation of material surfaces, but at first glance, is an unexpected technique to study the composition of microbial cell surfaces. Despite the fact that intimate contact between materials and microbial cell surfaces occurs in many

  8. Evaluating Superconducting YBCO Film Properties Using X-Ray Photoelectron Spectroscopy (Postprint)

    Science.gov (United States)

    2012-02-01

    AFRL-RZ-WP-TP-2012-0093 EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY PHOTOELECTRON SPECTROSCOPY (POSTPRINT) Paul N. Barnes...2012 Conference Paper Postprint 01 January 2002 – 01 January 2004 4. TITLE AND SUBTITLE EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY

  9. Pseudo-bimolecular [2+2] cycloaddition studied by time-resolved photoelectron spectroscopy

    DEFF Research Database (Denmark)

    Brogaard, Rasmus Y; Boguslavskiy, Andrey E; Schalk, Oliver

    2011-01-01

    The first study of pseudo-bimolecular cycloaddition reaction dynamics in the gas phase is presented. We used femtosecond time-resolved photoelectron spectroscopy (TRPES) to study the [2+2] photocycloaddition in the model system pseudo-gem-divinyl[2.2]paracyclophane. From X-ray crystal diffraction...

  10. Photoelectron spectroscopy and modeling of interface properties related to organic photovoltaic cells

    NARCIS (Netherlands)

    Fahlman, Mats; Sehati, Parisa; Osikowicz, Wojciech; Braun, Slawomir; Jong, de Michel P.; Brocks, Geert

    2013-01-01

    In this short review, we will give examples on how photoelectron spectroscopy (PES) assisted by models on interface energetics can be used to study properties important to bulk heterojunction type organic photovoltaic devices focusing on the well-known bulk heterojunction blend of poly(3-hexylthioph

  11. Photoelectron spectroscopy investigations of pyrrolo[1,2-a][1,10]phenanthroline derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Prelipceanu, M.; Prelipceanu, O.S. [University of Applied Sciences Wildau, Department of Engineering, Institute of Photonics and Physics Technologies, Friedrich-Engels Street 63, 15745 Wildau (Germany); Leontie, L. [Faculty of Physics, ' Al.I. Cuza' University, 11 Carol I Boulevard, 700506 Iasi (Romania)], E-mail: lleontie@uaic.ro; Danac, R. [Faculty of Chemistry, ' Al.I. Cuza' University, 11 Carol I Boulevard, 700506 Iasi (Romania)

    2007-08-20

    Thin films of new pyrrolo[1,2-a][1,10]phenanthroline derivatives have been investigated by ultraviolet photoelectron spectroscopy, with a view of future applications in optoelectronic devices. The electronic band structure of investigated compounds (for electron energies {<=}25 eV) is to a great extent determined by substituent (R = NO{sub 2}, Cl) induced transformations of molecular orbitals.

  12. In situ ALD experiments with synchrotron radiation photoelectron spectroscopy

    Science.gov (United States)

    Tallarida, Massimo; Schmeisser, Dieter

    2012-07-01

    In this contribution, we describe some features of atomic layer deposition (ALD) investigated by means of synchrotron radiation photoelemission spectroscopy (SR-PES). In particular, we show how the surface sensitivity of SR-PES combined with the in situ nature of our investigations can point out interactions between the substrate and ALD precursors. We observed changes on all substrates investigated, included Si, GaAs, Ru and their surface oxides. These interactions are extremely important during the first ALD cycles and induce modifications in the substrate, which might lead to its functionality enhancement.

  13. Decoherence in attosecond photoionization.

    Science.gov (United States)

    Pabst, Stefan; Greenman, Loren; Ho, Phay J; Mazziotti, David A; Santra, Robin

    2011-02-04

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration-interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, but it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion. As a consequence, even if the spectral bandwidth of the ionizing pulse exceeds the energy splittings among the hole states involved, perfectly coherent hole wave packets cannot be formed. For sufficiently large spectral bandwidth, the coherence can only be increased by increasing the mean photon energy.

  14. Hard x-ray photoelectron spectroscopy of chalcopyrite solar cell components

    Science.gov (United States)

    Gloskovskii, A.; Jenkins, C. A.; Ouardi, S.; Balke, B.; Fecher, G. H.; Dai, X.-F.; Gruhn, T.; Johnson, B.; Lauermann, I.; Caballero, R.; Kaufmann, C. A.; Felser, C.

    2012-02-01

    Hard x-ray photoelectron spectroscopy is used to examine the partial density of states of Cu(In,Ga)Se2 (CIGSe), a semiconducting component of solar cells. The investigated, thin Cu(In,Ga)Se2 films were produced by multi-stage co-evaporation. Details of the measured core level and valence band spectra are compared to the calculated density of states. The semiconducting type electronic structure of Cu(In,Ga)Se2 is clearly resolved in the hard x-ray photoelectron spectra.

  15. Noncollinear wave mixing of attosecond XUV and few-cycle optical laser pulses in gas-phase atoms: Toward multidimensional spectroscopy involving XUV excitations

    Science.gov (United States)

    Cao, Wei; Warrick, Erika R.; Fidler, Ashley; Neumark, Daniel M.; Leone, Stephen R.

    2016-11-01

    Ultrafast nonlinear spectroscopy, which records transient wave-mixing signals in a medium, is a powerful tool to access microscopic information using light sources in the radio-frequency and optical regimes. The extension of this technique towards the extreme ultraviolet (XUV) or even x-ray regimes holds the promise to uncover rich structural or dynamical information with even higher spatial or temporal resolution. Here, we demonstrate noncollinear wave mixing between weak XUV attosecond pulses and a strong near-infrared (NIR) few-cycle laser pulse in gas phase atoms (one photon of XUV and two photons of NIR). In the noncollinear geometry the attosecond and either one or two NIR pulses interact with argon atoms. Nonlinear XUV signals are generated in a spatially resolved fashion as required by phase matching. Different transition pathways can be identified from these background-free nonlinear signals according to the specific phase-matching conditions. Time-resolved measurements of the spatially gated XUV signals reveal electronic coherences of Rydberg wave packets prepared by a single XUV photon or XUV-NIR two-photon excitation, depending on the applied pulse sequences. These measurements open possible applications of tabletop multidimensional spectroscopy to the study of dynamics associated with valence or core excitation with XUV photons.

  16. Ultrafast Internal Conversion of Aromatic Molecules Studied by Photoelectron Spectroscopy using Sub-20 fs Laser Pulses

    Directory of Open Access Journals (Sweden)

    Toshinori Suzuki

    2014-02-01

    Full Text Available This article describes our recent experimental studies on internal conversion via a conical intersection using photoelectron spectroscopy. Ultrafast S2(ππ*–S1(nπ* internal conversion in pyrazine is observed in real time using sub-20 fs deep ultraviolet pulses (264 and 198 nm. While the photoelectron kinetic energy distribution does not exhibit a clear signature of internal conversion, the photoelectron angular anisotropy unambiguously reveals the sudden change of electron configuration upon internal conversion. An explanation is presented as to why these two observables have different sensitivities to internal conversion. The 198 nm probe photon energy is insufficient for covering the entire Franck-Condon envelopes upon photoionization from S2/S1 to D1/D0. A vacuum ultraviolet free electron laser (SCSS producing 161 nm radiation is employed to solve this problem, while its pulse-to-pulse timing jitter limits the time resolution to about 1 ps. The S2–S1 internal conversion is revisited using the sub-20 fs 159 nm pulse created by filamentation four-wave mixing. Conical intersections between D1(π−1 and D0(n−1 and also between the Rydberg state with a D1 ion core and that with a D0 ion core of pyrazine are studied by He(I photoelectron spectroscopy, pulsed field ionization photoelectron spectroscopy and one-color resonance-enhanced multiphoton ionization spectroscopy. Finally, ultrafast S2(ππ*–S1(ππ* internal conversion in benzene and toluene are compared with pyrazine.

  17. Experimental evidence for extreme surface sensitivity in Auger-Photoelectron Coincidence Spectroscopy (APECS) from solids

    Energy Technology Data Exchange (ETDEWEB)

    Liscio, A.; Gotter, R.; Ruocco, A.; Iacobucci, S.; Danese, A.G.; Bartynski, R.A.; Stefani, G

    2004-07-01

    Core hole creation and subsequent Auger decay processes are studied with unprecedented discrimination by Auger-Photoelectron Coincidence Spectroscopy (APECS). Early works in this field have already pointed out the intrinsic surface sensitivity of these experiments. However, it was not until recently that a model calculation was developed to quantitatively evaluate it. Here we present the first attempt to experimentally establish an effective target thickness for such experiments. The angular distribution of 3p{sub 3/2} photoelectron with kinetic energy of 160 eV is measured in coincidence with the M{sub 3}VV Auger electron with kinetic energy of 55 eV on a Cu (1 1 1) surface. Coincidence and non-coincidence photoelectron angular distributions display differences that, to large extent, are explained by confining the source of the coincident signal within the first two layers of Cu target, thus establishing an experimental upper limit for the effective target thickness of the APECS experiment.

  18. Beyond Attoseconds

    CERN Document Server

    Kaplan, A E

    2012-01-01

    We briefly review the pilot ideas on the generation of EM-pulses much shorter than already available sub-femtosecond pulses, and outline inroads and venues into the physics of pulses mush shorter than an attosecond (10^-18 s), in particular the so called zeptosecond (10^-21 s) and yoctosecond (10^-24 s) pulses that may allow one to operate on QED and nuclear as well as quark-gluon time plasma scales. We also very briefly outline the entire time-scale available in the existing universe, down to the ultimately short the so called Planck time ~ 10^-43 s, which is the time-scale of Big Bang, and the most significant time-scale-posts on the road to it.

  19. Photoelectron spectroscopy of the hydroxymethoxide anion, H2C(OH)O-

    Science.gov (United States)

    Oliveira, Allan M.; Lehman, Julia H.; McCoy, Anne B.; Lineberger, W. Carl

    2016-09-01

    We report the negative ion photoelectron spectroscopy of the hydroxymethoxide anion, H2C(OH)O-. The photoelectron spectra show that 3.49 eV photodetachment produces two distinct electronic states of the neutral hydroxymethoxy radical (H2C(OH)Oṡ). The H2C(OH)Oṡ ground state (X ˜ 2A) photoelectron spectrum exhibits a vibrational progression consisting primarily of the OCO symmetric and asymmetric stretches, the OCO bend, as well as combination bands involving these modes with other, lower frequency modes. A high-resolution photoelectron spectrum aids in the assignment of several vibrational frequencies of the neutral H2C(OH)Oṡ radical, including an experimental determination of the H2C(OH)Oṡ 2ν12 overtone of the H-OCO torsional vibration as 220(10) cm-1. The electron affinity of H2C(OH)Oṡ is determined to be 2.220(2) eV. The low-lying A ˜ 2A excited state is also observed, with a spectrum that peaks ˜0.8 eV above the X ˜ 2A state origin. The A ˜ 2A state photoelectron spectrum is a broad, partially resolved band. Quantum chemical calculations and photoelectron simulations aid in the interpretation of the photoelectron spectra. In addition, the gas phase acidity of methanediol is calculated to be 366(2) kcal mol-1, which results in an OH bond dissociation energy, D0(H2C(OH)O-H), of 104(2) kcal mol-1, using the experimentally determined electron affinity of the hydroxymethoxy radical.

  20. High-throughput Toroidal Grating Beamline for Photoelectron Spectroscopy at CAMD

    Science.gov (United States)

    Kizilkaya, O; Jiles, R W; Patterson, M C; Thibodeaux, C A; Poliakoff, E D; Sprunger, P T; Kurtz, R L; Morikawa, E

    2016-01-01

    A 5 meter toroidal grating (5m-TGM) beamline has been commissioned to deliver 28 mrad of bending magnet radiation to an ultrahigh vacuum endstation chamber to facilitate angle resolved photoelectron spectroscopy. The 5m-TGM beamline is equipped with Au-coated gratings with 300, 600 and 1200 lines/mm providing monochromatized synchrotron radiation in the energy ranges 25-70 eV, 50–120 eV and 100–240 eV, respectively. The beamline delivers excellent flux (~1014-1017 photons/sec/100mA) and a combined energy resolution of 189 meV for the beamline (at 1.0 mm slit opening) and HA-50 hemispherical analyzer was obtained at the Fermi level of polycrystalline gold crystal. Our preliminary photoelectron spectroscopy results of phenol adsorption on TiO2 (110) surface reveals the metal ion (Ti) oxidation. PMID:27134636

  1. Photoelectron and electron momentum spectroscopy of tetrahydrofuran from a molecular dynamical perspective.

    Science.gov (United States)

    Shojaei, S H Reza; Morini, Filippo; Deleuze, Michael S

    2013-03-07

    The results of experimental studies of the valence electronic structure of tetrahydrofuran employing He I photoelectron spectroscopy as well as Electron Momentum Spectroscopy (EMS) have been reinterpreted on the basis of Molecular Dynamical simulations employing the classical MM3 force field and large-scale quantum mechanical simulations employing Born-Oppenheimer Molecular Dynamics in conjunction with the dispersion corrected ωB97XD exchange-correlation functional. Analysis of the produced atomic trajectories demonstrates the importance of thermal deviations from the lowest energy path for pseudorotation, in the form of considerable variations of the ring-puckering amplitude. These deviations are found to have a significant influence on several outer-valence electron momentum distributions, as well as on the He I photoelectron spectrum.

  2. High Resolution Velocity Map Imaging Photoelectron Spectroscopy of the Beryllium Oxide Anion, BeO-

    Science.gov (United States)

    Dermer, Amanda Reed; Mascaritolo, Kyle; Heaven, Michael

    2016-06-01

    The photodetachment spectrum of BeO- has been studied using high resolution velocity map imaging photoelectron spectroscopy. The vibrational contours were imaged and compared with Franck-Condon simulations for the ground and excited states of the neutral. The electron affinity of BeO was measured for the first time, and anisotropies of several transitions were determined. Experimental findings are compared to high level ab initio calculations.

  3. Ultraviolet photoelectron spectroscopy of the valence bands of some Au alloys

    Energy Technology Data Exchange (ETDEWEB)

    Nicholson, J.A.; Riley, J.D.; Leckey, R.C.G.; Jenkin, J.G.; Liesegang, J.; Azoulay, J.

    1978-09-15

    Ultraviolet photoelectron spectra taken with 40.81-eV photons are presented for three series of Au alloys: AuGa, AuIn, and AuCd. The results are discussed with reference to similar work on a series of Ag alloys previously reported and are also compared with x-ray photoelectron spectroscopy data. The results are consistent with the previous work on Ag alloys in that the Au 5d doublet width and splitting are (i) independent of the secondary or alloying metal, and (ii) strongly dependent on the mean number of nearest Au neighbors. The behavior of the Au 5d bandwidth, as a function of Au concentration, as measured here using He II radiation, differs significantly from that measured previously using x-ray photoelectron spectroscopy. This difference cannot be attributed wholly to the difference in linewidth of the two-photon sources or to surface enrichment of the samples. The similar variations of the Ga, In, and Cd d bands as a function of Au concentration are discussed with reference to previous work on the alloys of AgIn and AgCd.

  4. X-ray and photoelectron spectroscopy of the structure, reactivity, and electronic structure of semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Hamad, Kimberly Sue [Univ. of California, Berkeley, CA (United States)

    2000-01-01

    Semiconductor nanocrystals are a system which has been the focus of interest due to their size dependent properties and their possible use in technological applications. Many chemical and physical properties vary systematically with the size of the nanocrystal and thus their study enables the investigation of scaling laws. Due to the increasing surface to volume ratio as size is decreased, the surfaces of nanocrystals are expected to have a large influence on their electronic, thermodynamic, and chemical behavior. In spite of their importance, nanocrystal surfaces are still relatively uncharacterized in terms of their structure, electronic properties, bonding, and reactivity. Investigation of nanocrystal surfaces is currently limited by what techniques to use, and which methods are suitable for nanocrystals is still being determined. This work presents experiments using x-ray and electronic spectroscopies to explore the structure, reactivity, and electronic properties of semiconductor (CdSe, InAs) nanocrystals and how they vary with size. Specifically, x-ray absorption near edge spectroscopy (XANES) in conjunction with multiple scattering simulations affords information about the structural disorder present at the surface of the nanocrystal. X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS) probe the electronic structure in terms of hole screening, and also give information about band lineups when the nanocrystal is placed in electric contact with a substrate. XPS of the core levels of the nanocrystal as a function of photo-oxidation time yields kinetic data on the oxidation reaction occurring at the surface of the nanocrystal.

  5. X-ray and photoelectron spectroscopy of the structure, reactivity, and electronic structure of semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Hamad, K.S.

    2000-05-01

    Semiconductor nanocrystals are a system which has been the focus of interest due to their size dependent properties and their possible use in technological applications. Many chemical and physical properties vary systematically with the size of the nanocrystal and thus their study enables the investigation of scaling laws. Due to the increasing surface to volume ratio as size is decreased, the surfaces of nanocrystals are expected to have a large influence on their electronic, thermodynamic, and chemical behavior. In spite of their importance, nanocrystal surfaces are still relatively uncharacterized in terms of their structure, electronic properties, bonding, and reactivity. Investigation of nanocrystal surfaces is currently limited by what techniques to use, and which methods are suitable for nanocrystals is still being determined. This work presents experiments using x-ray and electronic spectroscopies to explore the structure, reactivity, and electronic properties of semiconductor (CdSe, InAs) nanocrystals and how they vary with size. Specifically, x-ray absorption near edge spectroscopy (XANES) in conjunction with multiple scattering simulations affords information about the structural disorder present at the surface of the nanocrystal. X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS) probe the electronic structure in terms of hole screening, and also give information about band lineups when the nanocrystal is placed in electric contact with a substrate. XPS of the core levels of the nanocrystal as a function of photo-oxidation time yields kinetic data on the oxidation reaction occurring at the surface of the nanocrystal.

  6. Quantitative interpretation of molecular dynamics simulations for X-ray photoelectron spectroscopy of aqueous solutions

    Science.gov (United States)

    Olivieri, Giorgia; Parry, Krista M.; Powell, Cedric J.; Tobias, Douglas J.; Brown, Matthew A.

    2016-04-01

    Over the past decade, energy-dependent ambient pressure X-ray photoelectron spectroscopy (XPS) has emerged as a powerful analytical probe of the ion spatial distributions at the vapor (vacuum)-aqueous electrolyte interface. These experiments are often paired with complementary molecular dynamics (MD) simulations in an attempt to provide a complete description of the liquid interface. There is, however, no systematic protocol that permits a straightforward comparison of the two sets of results. XPS is an integrated technique that averages signals from multiple layers in a solution even at the lowest photoelectron kinetic energies routinely employed, whereas MD simulations provide a microscopic layer-by-layer description of the solution composition near the interface. Here, we use the National Institute of Standards and Technology database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to quantitatively interpret atom-density profiles from MD simulations for XPS signal intensities using sodium and potassium iodide solutions as examples. We show that electron inelastic mean free paths calculated from a semi-empirical formula depend strongly on solution composition, varying by up to 30% between pure water and concentrated NaI. The XPS signal thus arises from different information depths in different solutions for a fixed photoelectron kinetic energy. XPS signal intensities are calculated using SESSA as a function of photoelectron kinetic energy (probe depth) and compared with a widely employed ad hoc method. SESSA simulations illustrate the importance of accounting for elastic-scattering events at low photoelectron kinetic energies (hoc method systematically underestimates the preferential enhancement of anions over cations. Finally, some technical aspects of applying SESSA to liquid interfaces are discussed.

  7. Electron mean free path from angle-dependent photoelectron spectroscopy of aerosol particles

    CERN Document Server

    Goldmann, Maximilian; West, Adam H C; Yoder, Bruce L; Signorell, Ruth

    2015-01-01

    We propose angle-resolved photoelectron spectroscopy of aerosol particles as an alternative way to determine the electron mean free path of low energy electrons in solid and liquid materials. The mean free path is obtained from fits of simulated photoemission images to experimental ones over a broad range of different aerosol particle sizes. The principal advantage of the aerosol approach is twofold. Firstly, aerosol photoemission studies can be performed for many different materials, including liquids. Secondly, the size-dependent anisotropy of the photoelectrons can be exploited in addition to size-dependent changes in their kinetic energy. These finite size effects depend in different ways on the mean free path and thus provide more information on the mean free path than corresponding liquid jet, thin film, or bulk data. The present contribution is a proof of principle employing a simple model for the photoemission of electrons and preliminary experimental data for potassium chloride aerosol particles.

  8. Functional materials for information and energy technology: Insights by photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Müller, Martina [Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich (Germany); JARA Jülich-Aachen Research Alliance, Forschungszentrum Jülich, 52425 Jülich (Germany); Fakultät für Physik, Universität Duisburg-Essen, 47048 Duisburg (Germany); Nemšák, Slavomír; Plucinski, Lukasz [Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich (Germany); JARA Jülich-Aachen Research Alliance, Forschungszentrum Jülich, 52425 Jülich (Germany); Schneider, Claus M., E-mail: c.m.schneider@fz-juelich.de [Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich (Germany); JARA Jülich-Aachen Research Alliance, Forschungszentrum Jülich, 52425 Jülich (Germany); Fakultät für Physik, Universität Duisburg-Essen, 47048 Duisburg (Germany)

    2016-04-15

    Highlights: • Photoemission spectro/microscopy studies of functional material systems. • Hard X-ray photoemission spectroscopy from magnetic semiconductors and insulators. • Information depth studies in hard X-ray photoemission microscopy. • Soft X-ray standing wave ambient pressure photoemission spectroscopy from liquid films. - Abstract: The evolution of both information and energy technology is intimately connected to complex condensed matter systems, the properties of which are determined by electronic and chemical interactions and processes on a broad range of length and time scales. Dedicated photoelectron spectroscopy and spectromicroscopy experiments can provide important insights into fundamental phenomena and applied functionalities. We discuss some recent methodological developments with application to relevant questions in spintronics, and towards operando studies of resistive switching and electrochemical processes.

  9. X-ray photoelectron spectroscopy study of the effects of ultrapure water on GaAs

    Science.gov (United States)

    Massies, J.; Contour, J. P.

    1985-06-01

    X-ray photoelectron spectroscopy has been used to investigate the effects of de-ionized water on chemical etched GaAs surfaces. When the treatment with water is performed in static conditions (stagnant water) a Ga-rich oxide layer is formed on GaAs at the rate of 10-20 Å h-1. In contrast, when the GaAs surface is treated in dynamic conditions (running water), no oxide buildup is observed. Moreover, running water can remove the oxide film formed in static conditions, as well as oxidized layers due to air exposure. These results are discussed in the framework of cleaning prior to molecular beam epitaxy.

  10. Assessment of nanocomposite photonic systems with the X-ray photoelectron spectroscopy

    Institute of Scientific and Technical Information of China (English)

    L. Minati; G. Speranza; M. Anderle; M. Ferrari; A. Chiasera; G. C. Righini

    2007-01-01

    The chemical compositions of Ag-Er co-doped phosphate and silicate glasses were investigated with X-ray photoelectron spectroscopy with the purpose to identify the chemical state of silver. The analysis of the Ag 3d core lines show the presence of nanometer-sized silver particles in each of the annealed samples, even if these Ag 3d lines appear to be very different from each other. We explain these results as a different interaction of silver with the two glasses matrix, which leads to a different nucleation rate of the Ag clusters.

  11. Structural Investigation of SBGESE Glasses by High Resolution X-Ray Photoelectron Spectroscopy

    Directory of Open Access Journals (Sweden)

    R. Golovchak

    2011-01-01

    Full Text Available The evolution of the structure of Sb8Ge32Se60 (Z=2.72 and Sb20Ge20Se60 (Z=2.60 chalcogenide glasses is determined by high resolution X-ray photoelectron spectroscopy. Glasses with Z=2.60 the structure consists of deformed tetrahedra and pyramids, in which at least one Se atom is substituted by Ge or Sb atom. For the Z=2.72 structure consisting of shared pyramids and tetrahedra with two or more Se atoms substituted by the cations. At the same time, Se-Se dimers are present in both compositions.

  12. Single-order laser high harmonics in XUV for ultrafast photoelectron spectroscopy of molecular wavepacket dynamics

    Directory of Open Access Journals (Sweden)

    Mizuho Fushitani

    2016-11-01

    Full Text Available We present applications of extreme ultraviolet (XUV single-order laser harmonics to gas-phase ultrafast photoelectron spectroscopy. Ultrashort XUV pulses at 80 nm are obtained as the 5th order harmonics of the fundamental laser at 400 nm by using Xe or Kr as the nonlinear medium and separated from other harmonic orders by using an indium foil. The single-order laser harmonics is applied for real-time probing of vibrational wavepacket dynamics of I2 molecules in the bound and dissociating low-lying electronic states and electronic-vibrational wavepacket dynamics of highly excited Rydberg N2 molecules.

  13. Hexamethylcyclopentadiene: time-resolved photoelectron spectroscopy and ab initio multiple spawning simulations

    DEFF Research Database (Denmark)

    Wolf, T. J. A.; Kuhlman, Thomas Scheby; Schalk, O.

    2014-01-01

    comparing time-resolved photoelectron spectroscopy (TRPES) with ab initio multiple spawning (AIMS) simulations on the MS-MR-CASPT2 level of theory. We disentangle the relationship between two phenomena that dominate the immediate molecular response upon light absorption: a spectrally dependent delay...... replaced by ‘‘hydrogen atoms’’ having mass 15 and TRPES spectra were calculated. These showed an induction time of (108 10) fs which could directly be assigned to progress along a torsional mode leading to the intersection seam with the molecular ground state. In a stepladder-type approach, the close...

  14. Chemical Reaction Between Polyvinyl Alcohol and Titanate Coupling Agent with X-Ray Photoelectron Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    LI Bei-xing; ZHANG Wen-sheng

    2003-01-01

    The chemical reaction between polyvinyl alcohol (PVA) and tri(dioctylpyrophosphoryloxy) isopropyl titanate (NDZ-201) was studied using X-ray photoelectron spectroscopy (XPS).The results show that some C-OH functional groups of PVA react with the titanate coupling agent to form CPVA-O-Ti-O-CPVA bond.The cross-linking of the PVA chains occurs through the formation of CPVA-O-Ti-O-CPVA bonds and produces a three dimensional hydrophobic polymer network.Accordingly,the mechanism is proposed that the titanate coupling agent improves the moisture sensitivity of high alumina cement/polyvinyl alcohol (HAC/PVA) based macro defect free (MDF) composite material.

  15. Study on RE-Al-Zr-C-N Coating by X-ray Photoelectron Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    韦永德; 马楠; 侯仰龙

    2001-01-01

    Thermal diffusion of coating on 45 steel with rare earths, zirconium, aluminum, carbon and nitrogen was reported. Through X-ray photoelectron spectrum, the binding energy of permeated elements and their existence states were analyzed. Their existence on the surface of treated steel was confirmed by scanning electronic microscopy and energy dispersive spectroscopy. The results show that the rare earth acts as an activator and accelerator of the permeating of other elements. The effect of rare earths on aluminum is greater than that on zirconium.

  16. In situ photoelectron spectroscopy of molecular-beam-epitaxy grown surfaces

    CERN Document Server

    Oshima, M; Okabayashi, J; Ono, K

    2003-01-01

    Two in situ high-resolution synchrotron radiation photoelectron spectroscopy (SRPES) systems combined with a molecular beam epitaxy (MBE) chamber for III-V compound semiconductors and a laser MBE chamber for strongly correlated oxide films, respectively, have been designed and fabricated to analyze intrinsic and surface/interface electronic structures of these unique materials. The importance of the in situ SRPES has been demonstrated by the results of 1) Si surface nanostructures, 2) GaAs surfaces/interfaces and nanostructures, 3) MnAs magnetic nanostructures, and 4) strongly-correlated La sub 1 sub - sub x Sr sub x MnO sub 3 surfaces/interfaces and superstructures.

  17. Study of selected benzyl azides by UV photoelectron spectroscopy and mass spectrometry

    Science.gov (United States)

    Pinto, R. M.; Olariu, R. I.; Lameiras, J.; Martins, F. T.; Dias, A. A.; Langley, G. J.; Rodrigues, P.; Maycock, C. D.; Santos, J. P.; Duarte, M. F.; Fernandez, M. T.; Costa, M. L.

    2010-09-01

    Benzyl azide and the three methylbenzyl azides were synthesized and characterized by mass spectrometry (MS) and ultraviolet photoelectron spectroscopy (UVPES). The electron ionization fragmentation mechanisms for benzyl azide and their methyl derivatives were studied by accurate mass measurements and linked scans at constant B/ E. For benzyl azide, in order to clarify the fragmentation mechanism, labelling experiments were performed. From the mass analysis of methylbenzyl azides isomers it was possible to differentiate the isomers ortho, meta and para. The abundance and nature of the ions resulting from the molecular ion fragmentation, for the three distinct isomers of substituted benzyl azides, were rationalized in terms of the electronic properties of the substituent. Concerning the para-isomer, IRC calculations were performed at UHF/6-31G(d) level. The photoionization study of benzyl azide, with He(I) radiation, revealed five bands in the 8-21 eV ionization energies region. From every photoelectron spectrum of methylbenzyl azides isomers it has been identified seven bands, on the same range as the benzyl azide. Interpretation of the photoelectron spectra was accomplished applying Koopmans' theorem to the SCF orbital energies obtained at HF/6-311++G(d, p) level.

  18. Advancements in time-resolved x-ray laser induced time-of-flight photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A J; Dunn, J; Widmann, K; Ao, T; Ping, Y; Hunter, J; Ng, A

    2005-07-28

    Time-resolved soft x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) metal foils and bulk semiconductors. Single-shot soft x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution was used in combination with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated metal foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.3-2.5 mJ laser energy focused in a large 500 x 700 {micro}m{sup 2} spot to create heated conditions of 0.2-1.8 x 10{sup 12} W cm{sup -2} intensity. The unique LLNL COMET compact tabletop soft x-ray laser source provided the necessary high photon flux, highly monoenergetic, picosecond pulse duration, and coherence for observing the evolution of changes in the valence band electronic structure of laser heated metals and semiconductors with picosecond time resolution. This work demonstrates the continuing development of a powerful new technique for probing reaction dynamics and changes of local order on surfaces on their fundamental timescales including phenomena such as non-thermal melting, chemical bond formation, intermediate reaction steps, and the existence of transient reaction products.

  19. Functionalized tellurols: synthesis, spectroscopic characterization by photoelectron spectroscopy, and quantum chemical study.

    Science.gov (United States)

    Khater, Brahim; Guillemin, Jean-Claude; Bajor, Gábor; Veszprémi, Tamás

    2008-03-03

    Ethene-, cyclopropane-, 3-butene-, and cyclopropanemethanetellurol have been synthesized by reaction of tributyltin hydride with the corresponding ditellurides and characterized by 1H, 13C, and 125Te NMR spectroscopy and high-resolution mass spectrometry. The tellurols of this series, with a gradually increasing distance between the tellurium atom and the unsaturated group, have been studied by photoelectron spectroscopy and quantum chemical calculations. Two stable conformations of ethenetellurol and cyclopropanetellurol, five of allyltellurol, and four of cyclopropanemethanetellurol were found. In the photoelectron spectrum of vinyltellurol, the huge split between the first two bands indicates a direct interaction between the tellurium lone electron pair and the double bond. In the allyl derivative, a hyperconjugation effect was found for the most stable conformers. In contrast to the vinyl compounds, no direct interaction between the lone electron pair of X (X = O, S, Se, and Te) and the three-membered ring could be observed in the cyclopropyl derivatives. A hyperconjugation-like effect, which is independent of the relative orientation of the X-H group, is found to increase from S to Te. Thus, the type and extent of the interaction between the TeH group and an unsaturated or cyclopropyl moiety are clarified while the first comparison of interactions between the nonradioactive unsaturated chalcogen derivatives is performed.

  20. Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lai-Sheng, E-mail: Lai-Sheng-Wang@brown.edu [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)

    2015-07-28

    Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent development in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES.

  1. Probing attosecond pulse structures by XUV-induced hole dynamics

    CERN Document Server

    You, Jhih-An; Dahlström, Jan Marcus

    2015-01-01

    We investigate a two-photon ionization process in neon by an isolated attosecond pump pulse and two coherent extreme ultraviolet probe fields. The probe fields, tuned to the 2s-2p transition in the residual ion, allow for coherent control of the photoelectron via indirect interactions with the hole. We show that the photoelectron-ion coincidence signal contains an interference pattern that can be used to reconstruct the temporal structure of attosecond pump pulses. Our results are supported by simulations based on time-dependent configuration-interaction singles and lowest-order perturbation theory within second quantization.

  2. Ambient pressure photoelectron spectroscopy: a new tool for surface science and nanotechnology

    Energy Technology Data Exchange (ETDEWEB)

    Salmeron, Miquel; Salmeron, Miquel; Schlogl, Robert

    2008-03-12

    Progress in science often follows or parallels the development of new techniques. The optical microscope helped convert medicine and biology from a speculative activity in old times to today's sophisticated scientific disciplines. The telescope changed the study and interpretation of heavens from mythology to science. X-ray diffraction enabled the flourishing of solid state physics and materials science. The technique object of this review, Ambient Pressure Photoelectron Spectroscopy or APPES for short, has also the potential of producing dramatic changes in the study of liquid and solid surfaces, particularly in areas such as atmospheric, environment and catalysis sciences. APPES adds an important missing element to the host of techniques that give fundamental information, i.e., spectroscopy and microscopy, about surfaces in the presence of gases and vapors, as encountered in industrial catalysis and atmospheric environments. APPES brings electron spectroscopy into the realm of techniques that can be used in practical environments. Decades of surface science in ultra high vacuum (UHV) has shown the power of electron spectroscopy in its various manifestations. Their unique property is the extremely short elastic mean free path of electrons as they travel through condensed matter, of the order of a few atomic distances in the energy range from a few eV to a few thousand eV. As a consequence of this the information obtained by analyzing electrons emitted or scattered from a surface refers to the top first few atomic layers, which is what surface science is all about. Low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), Ultraviolet photoelectron spectroscopy (UPS), and other such techniques have been used for decades and provided some of the most fundamental knowledge about surface crystallography, composition and electronic structure available today. Unfortunately the high interaction cross section of

  3. Dealloying of Cu{sub x}Au studied by hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rajput, Parasmani, E-mail: parasmani.rajput@northwestern.edu [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Gupta, Ajay [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 017 (India); Detlefs, Blanka [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Kolb, Dieter M. [Institute for Electrochemistry, University of Ulm, D-89069 Ulm (Germany); Potdar, Satish [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 017 (India); Zegenhagen, Jörg [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France)

    2013-10-15

    Highlights: ► The shift in binding energy of Cu and Au lines in CuAu alloys is opposite to expected from the nobility of the elements. ► The magnitude of the chemical shifts of the metal lines in CuAu alloys is strongly influenced by finite size effects and disorder. ► Cu 3s and/or Au 4f cross-sections are not well described by theory (Scofield). The Cu 3s photoabsorption cross-section seems to be strongly overestimated. ► We find/confirm that (CuAu) dealloying proceeds into depth like a spinodal decomposition. -- Abstract: We studied pristine and leached ultra-thin Cu{sub x}Au (x ≈ 4) films by hard X-ray photoelectron spectroscopy. The Au 4f and Cu 3s core levels show a shift in binding energy which is opposite to expected from the nobility of the elements, which is explained by charge transfer involving differently screening s and d valence levels of the elements [W. Eberhardt, S.C. Wu, R. Garrett, D. Sondericker, F. Jona, Phys. Rev. B 31 (1985) 8285]. The magnitude of the chemical shifts of the metal lines is strongly influenced by the finite size and disorder of the films. Angular dependent photoelectron emission allowed to assess the alloy composition as a function of depth larger than 5 nm. The potential controlled dealloying proceeds into depth like a spinodal decomposition with Cu going into solution and the remaining Au accumulating in the surface region. The compositional gradient did not lead to a significant broadening of the metal photoelectron lines suggesting a non-local screening mechanism.

  4. X-ray photoelectron spectroscopy of graphitic carbon nanomaterials doped with heteroatoms.

    Science.gov (United States)

    Susi, Toma; Pichler, Thomas; Ayala, Paola

    2015-01-01

    X-ray photoelectron spectroscopy (XPS) is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS.

  5. Conformation-Selective Resonant Photoelectron Spectroscopy via Dipole-Bound States of Cold Anions.

    Science.gov (United States)

    Huang, Dao-Ling; Liu, Hong-Tao; Ning, Chuan-Gang; Wang, Lai-Sheng

    2015-06-18

    Molecular conformation is important in chemistry and biochemistry. Conformers connected by low energy barriers can only be observed at low temperatures and are difficult to be separated. Here we report a new method to obtain conformation-selective spectroscopic information about dipolar molecular radicals via dipole-bound excited states of the corresponding anions cooled in a cryogenic ion trap. We observed two conformers of cold 3-hydroxyphenoxide anions [m-HO(C6H4)O(-)] in high-resolution photoelectron spectroscopy and measured different electron affinities, 18,850(8) and 18,917(5) cm(-1), for the syn and anti 3-hydroxyphenoxy radicals, respectively. We also observed dipole-bound excited states for m-HO(C6H4)O(-) with different binding energies for the two conformers due to the different dipole moments of the corresponding 3-hydroxyphenoxy radicals. Excitations to selected vibrational levels of the dipole-bound states result in conformation-selective photoelectron spectra. This method should be applicable to conformation-selective spectroscopic studies of any anions with dipolar neutral cores.

  6. Atomic and Molecular Photoelectron and Auger Electron SpectroscopyStudies Using Synchrotron Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Southworth, Stephen H.

    1982-01-01

    Electron spectroscopy, combined with synchrotron radiation, was used to measure the angular distributions of photoelectrons and Auger electrons from atoms and molecules as functions of photon energy. The branching ratios and partial cross sections were a 130 measured in certain cases. By comparison with theoretical calculations, the experimental results are interpreted in terms of the characteristic electronic structure and ionization dynamics of the atomic or molecular sample. The time structure of the synchrotron radiation source was used to record time-of-flight (TOF) spectra o f the ejected electrons. The ''a double-angle-TOF'' method for the measurement of photoelectron angular distributions is discussed. This technique offers the advantages of increased electron collect ion efficiency and the elimination of certain systematic errors. Several results were obtained for Xe using photon energies in the range hv {approx_equal} 60-190 eV, where excitation and ionization of the inner-subshell 4d electrons dominates. The 4d asymmetry parameter {beta} exhibits strong oscillations with energy, in agreement with several theoretical calculations. As predicted, the 5p asymmetry parameter was observed to deviate strongly from that calculated using the independent-electron model, due to intershell correlation with the 4d electrons.

  7. X-ray photoelectron spectroscopy of graphitic carbon nanomaterials doped with heteroatoms

    Directory of Open Access Journals (Sweden)

    Toma Susi

    2015-01-01

    Full Text Available X-ray photoelectron spectroscopy (XPS is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS.

  8. Ambient-Pressure X-ray Photoelectron Spectroscopy through Electron Transparent Graphene Membranes

    CERN Document Server

    Kraus, Jurgen; Gunther, Sebastian; Gregoratti, Luca; Amati, Matteo; Kiskinova, Maya; Yulaev, Alexander; Vlassiouk, Ivan; Kolmakov, Andrei

    2014-01-01

    Photoelectron spectroscopy (PES) and microscopy are highly demanded for exploring morphologically complex solid-gas and solid-liquid interfaces under realistic conditions, but the very small electron mean free path inside the dense media imposes serious experimental challenges. Currently, near ambient pressure PES is conducted using sophisticated and expensive electron energy analyzers coupled with differentially pumped electron lenses. An alternative economical approach proposed in this report uses ultrathin graphene membranes to isolate the ambient sample environment from the PES detection system. We demonstrate that the graphene membrane separating windows are both mechanically robust and sufficiently transparent for electrons in a wide energy range to allow PES of liquid and gaseous water. The reported proof-of-principle experiments also open a principal possibility to probe vacuum-incompatible toxic or reactive samples enclosed inside the hermetic environmental cells.

  9. Materials characterization by photoelectron spectroscopy; Caracterizacao de materiais por espectroscopia de fotoeletrons

    Energy Technology Data Exchange (ETDEWEB)

    Nascente, P.A.P., E-mail: nascente@ufscar.b [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    Low energy electrons are suitable for investigating surfaces due to their low mean free path in solids, which correspond to a few atomic layers (0.5 to 3.0 nm), and could be used in one of the following ways: incident electrons cause the emission of backscattered and secondary electrons and the electrons are excited by irradiated photons. The first case includes the emission of Auger electrons, while photoemission corresponds to the second case. X-ray photoelectron spectroscopy (XPS) is one of the most used surface analysis techniques since it is able to identify not only the surface constituents but also their chemical states. XPS can be employed in several areas of science and engineering, but in this report it will be presented only few examples of its use in the characterization of metallic materials, with an emphasis on thin films of noble and transition metals. (author)

  10. X-ray photoelectron spectroscopy study of excimer laser treated alumina films

    Science.gov (United States)

    Georgiev, D. G.; Kolev, K.; Laude, L. D.; Mednikarov, B.; Starbov, N.

    1998-01-01

    Amorphous alumina layers are deposited on a single crystal Si substrate by a e-gun evaporation technique. These films are then thermally annealed in oxygen to be crystallized and, further, irradiated with an excimer laser beam. At each stage of the film preparation, an x-ray photoelectron spectroscopy analysis is performed at the film surface and in depth, upon ion beam grinding. Results give evidence for the formation of an aluminosilicate upon thermal annealing of the film in oxygen. At the surface itself, this compound is observed to decompose upon excimer laser irradiation at energy densities exceeding 1.75 J/cm2, giving rise to free Si atoms and SiO2, however with complete disappearance of Al atoms. Model photochemical reactions are proposed to explain such transformations.

  11. Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zanni, Martin Thomas [Univ. of California, Berkeley, CA (United States)

    1999-12-01

    This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents.

  12. [Surface and interface analysis of PTCDA/ITO using X-ray photoelectron spectroscopy (XPS)].

    Science.gov (United States)

    Ou, Gu-ping; Song, Zhen; Gui, Wen-ming; Zhang, Fu-jia

    2006-04-01

    X-ray photoelectron spectroscopy (XPS) of surface and interface of PTCDA/ITO in PTCDA/p-Si organic-on-inorganic photoelectric detector was investigated. From C1s fine spectrum we found that the binding energy of C atoms in perylene rings was 284.6 eV; and the binding energy of C atoms in acid radical was 288.7 eV; moreover, some C atoms were oxidized by O atoms from ITO. The binding energy of O atoms in C=O bonds and C-O-C bonds was 531.5 and 533.4 eV, respectively. At the interface, the peak of high binding energy in C1s spectrum disappeared, and the main peak shifted toward lower binding energy.

  13. Determination of band profiles in GaN films using hard X-ray photoelectron spectroscopy

    Science.gov (United States)

    Saito, Shinji; Yoshiki, Masahiko; Nunoue, Shinya; Sano, Nobuyuki

    2017-02-01

    We investigated band-profile control by introducing interlayers between a semiconductor and metal contact layers to improve the electrical properties of GaN-based semiconductor devices. We evaluated the electronic structure of the semiconductor surface and the metal/semiconductor interface by hard X-ray photoelectron spectroscopy. We also performed Monte Carlo simulations using the Boltzmann transport equation under the potential profile obtained using the Poisson equation. The band profile in the semiconductor substrate was then examined by comparing the energy spectra from the simulations with those from the experiments. We obtained good agreement between the two results. The present experimental and theoretical methods allow one to determine the band profile near the surface of a semiconductor as well as that in a metal interface. This approach may become a useful tool in the design and/or evaluation of processing conditions.

  14. X-Ray Laser Induced Photoelectron Spectroscopy for Single-State Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A J; Dunn, J; van Buuren, T; Hunter, J

    2004-07-14

    We demonstrate single-shot x-ray laser induced time-of-flight photoelectron spectroscopy on metal and semiconductor surfaces with picosecond time resolution. The LLNL COMET compact tabletop x-ray laser source provides the necessary high photon flux (>10{sup 12}/pulse), monochromaticity, picosecond pulse duration, and coherence for probing ultrafast changes in the chemical and electronic structure of these materials. Static valence band and shallow core-level photoemission spectra are presented for ambient temperature polycrystalline Cu foils and Ge(100). Surface contamination was removed by UV ozone cleaning prior to analysis. The ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials.

  15. Structures of cycloserine and 2-oxazolidinone probed by X-ray photoelectron spectroscopy

    CERN Document Server

    Ahmed, Marawan; Acres, Robert G; Prince, Kevin C

    2013-01-01

    The electronic structures and properties of 2-oxazolidinone and the related compound cycloserine (CS) have been investigated using core and valence photoelectron spectroscopy and theoretical calculations. Isomerization of the central oxazolidine heterocycle and the addition of an amino group yields cycloserine. Theory correctly predicts the C, N and O 1s core spectra, and additionally we report theoretical natural bond orbital (NBO) charges. The valence ionization energies are also in agreement with theory and previous measurements. Although the lowest binding energy part of the spectra of the two compounds show superficial similarities, analysis of the charge densities of the frontier orbitals indicates substantial reorganization of the wave functions as a result of isomerization. The Highest Occupied Molecular Orbital of CS has leading carbonyl {\\pi} character with contributions from other heavy atoms in the molecule, while the Highest Occupied Molecular Orbital of 2-oxazolidinone has leading nitrogen, carb...

  16. Coincidence and covariance data acquisition in photoelectron and -ion spectroscopy. II. Analysis and applications

    Science.gov (United States)

    Mikosch, Jochen; Patchkovskii, Serguei

    2013-10-01

    We use an analytical theory of noisy Poisson processes, developed in the preceding companion publication, to compare coincidence and covariance measurement approaches in photoelectron and -ion spectroscopy. For non-unit detection efficiencies, coincidence data acquisition (DAQ) suffers from false coincidences. The rate of false coincidences grows quadratically with the rate of elementary ionization events. To minimize false coincidences for rare event outcomes, very low event rates may hence be required. Coincidence measurements exhibit high tolerance to noise introduced by unstable experimental conditions. Covariance DAQ on the other hand is free of systematic errors as long as stable experimental conditions are maintained. In the presence of noise, all channels in a covariance measurement become correlated. Under favourable conditions, covariance DAQ may allow orders of magnitude reduction in measurement times. Finally, we use experimental data for strong-field ionization of 1,3-butadiene to illustrate how fluctuations in experimental conditions can contaminate a covariance measurement, and how such contamination can be detected.

  17. Self-assembled heterogeneous argon/neon core-shell clusters studied by photoelectron spectroscopy.

    Science.gov (United States)

    Lundwall, M; Pokapanich, W; Bergersen, H; Lindblad, A; Rander, T; Ohrwall, G; Tchaplyguine, M; Barth, S; Hergenhahn, U; Svensson, S; Björneholm, O

    2007-06-01

    Clusters formed by a coexpansion process of argon and neon have been studied using synchrotron radiation. Electrons from interatomic Coulombic decay as well as ultraviolet and x-ray photoelectron spectroscopy were used to determine the heterogeneous nature of the clusters and the cluster structure. Binary clusters of argon and neon produced by coexpansion are shown to exhibit a core-shell structure placing argon in the core and neon in the outer shells. Furthermore, the authors show that 2 ML of neon on the argon core is sufficient for neon valence band formation resembling the neon solid. For 1 ML of neon the authors observe a bandwidth narrowing to about half of the bulk value.

  18. Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zanni, Martin T.

    1999-12-17

    This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents.

  19. Thermal oxidation of vanadium-free Ti alloys: An X-ray photoelectron spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, Maria Francisca, E-mail: mflopez@icmm.csic.es [Department of Surfaces and Coatings, ICMM-CSIC, Sor Juana Ines de la Cruz, 3, Cantoblanco, 28049 Madrid (Spain); Gutierrez, Alejandro [Departamento de Fisica Aplicada and Instituto Nicolas Cabrera, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Jimenez, Jose Antonio [Centro Nacional de Investigaciones Metalurgicas, CSIC, Avda. Gregorio del Amo 8, E-28040 Madrid (Spain); Martinesi, Maria; Stio, Maria; Treves, Cristina [Department of Biochemical Sciences of University of Florence, Viale Morgagni 50, 50134 Florence (Italy)

    2010-04-06

    In the present work, X-ray photoelectron spectroscopy (XPS) was used to study the surface chemical composition of three alloys for biomedical applications: Ti-7Nb-6Al, Ti-13Nb-13Zr and Ti-15Zr-4Nb. The surface of these alloys was modified by annealing in air at 750 deg. C for different times with the aim of developing an oxide thick layer on top. The evolution of surface composition with annealing time was studied by XPS, and compared with the composition of the native oxide layer present on the samples before annealing. Two different oxidation trends were observed depending on the alloying elements and their corresponding diffusion kinetics, which give rise to different chemical species at the topmost layers. These results were linked with an evaluation of the biological response of the alloys by bringing them in contact with human peripheral blood mononuclear cells (PBMC).

  20. Probing electronic properties of molecular engineered zinc oxide nanowires with photoelectron spectroscopy.

    Science.gov (United States)

    Aguilar, Carlos A; Haight, Richard; Mavrokefalos, Anastassios; Korgel, Brian A; Chen, Shaochen

    2009-10-27

    ZnO nanowires (NWs) are emerging as key elements for new lasing, photovoltaic and sensing applications but elucidation of their fundamental electronic properties has been hampered by a dearth of characterization tools capable of probing single nanowires. Herein, ZnO NWs were synthesized in solution and integrated into a low energy photoelectron spectroscopy system, where quantitative optical measurements of the NW work function and Fermi level location within the band gap were collected. Next, the NWs were decorated with several dipolar self-assembled monolayers (SAMs) and control over the electronic properties is demonstrated, yielding a completely tunable hybrid electronic material. Using this new metrology approach, a host of other extraordinary interfacial phenomena could be explored on nanowires such as spatial dopant profiling or heterostructures.

  1. A novel approach to angular-resolved X-ray photoelectron spectroscopy depth-profiling

    Energy Technology Data Exchange (ETDEWEB)

    Stanchev, A.; Ignatova, V.; Ghelev, Ch. E-mail: chghelev@ie.bas.bg

    2000-05-02

    The angular-resolved-X-ray photoelectron spectroscopy (AR-XPS) technique is chosen to investigate the O redistribution on the surface of yttria-stabilized ZrO{sub 2} crystals during 10 keV He{sup +} ion bombardment. The data processing is performed by means of a newly-developed version of the 'Box-car' function method. An energy correction of the inelastic mean free paths (IMFP) of the elements present is performed and the elements peak areas are normalized with respect to surface carbon layer. An algorithm is described, which is tested and applied to the angular-dependent XPS data, and the true elements' depth-profiles are thus obtained.

  2. Disentangling Multichannel Photodissociation Dynamics in Acetone by Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy.

    Science.gov (United States)

    Maierhofer, Paul; Bainschab, Markus; Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E; Koch, Markus

    2016-08-18

    For the investigation of photoinduced dynamics in molecules with time-resolved pump-probe photoionization spectroscopy, it is essential to obtain unequivocal information about the fragmentation behavior induced by the laser pulses. We present time-resolved photoelectron-photoion coincidence (PEPICO) experiments to investigate the excited-state dynamics of isolated acetone molecules triggered by two-photon (269 nm) excitation. In the complex situation of different relaxation pathways, we unambiguously identify three distinct pump-probe ionization channels. The high selectivity of PEPICO detection allows us to observe the fragmentation behavior and to follow the time evolution of each channel separately. For channels leading to fragment ions, we quantitatively obtain the fragment-to-parent branching ratio and are able to determine experimentally whether dissociation occurs in the neutral molecule or in the parent ion. These results highlight the importance of coincidence detection for the interpretation of time-resolved photochemical relaxation and dissociation studies if multiple pathways are present.

  3. Attosecond nanoscale near-field sampling

    CERN Document Server

    Förg, Benjamin; Suessmann, Frederik; Foerster, Michael; Krueger, Michael; Ahn, Byung-Nam; Wintersperger, Karen; Zherebtsov, Sergey; Guggenmos, Alexander; Pervak, Vladimir; Kessel, Alexander; Trushin, Sergei; Azzeer, Abdallah; Stockman, Mark; Kim, Dong-Eon; Krausz, Ferenc; Hommelhoff, Peter; Kling, Matthias

    2015-01-01

    The promise of ultrafast light field driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical nearfields from light interaction with nanostructures with sub cycle resolution. Here, we experimentally demonstrate attosecond nearfield retrieval with a gold nanotip using streaking spectroscopy. By comparison of the results from gold nanotips to those obtained for a noble gas, the spectral response of the nanotip near field arising from laser excitation can be extracted. Monte Carlo MC trajectory simulations in near fields obtained with the macroscopic Maxwells equations elucidate the streaking mechanism on the nanoscale.

  4. High resolution photoelectron spectroscopy and femtosecond intramolecular dynamics using supersonic molecular beams

    Energy Technology Data Exchange (ETDEWEB)

    Niu, B.

    1992-09-01

    High resolution He I[alpha] photoelectron spectroscopy of formaldehyde and ketene and their deuterated compounds, are reported. The combination of a (H2CO) double-pass high-resolution electron-energy analyzer and effective rotational cooling of the sample by supersonic expansion enable the spectroscopy of these molecular cations. The vibrational autocorrelation functions are calculated from the high-resolution photoelectron spectra, shedding light on the ultrafast intramolecular dynamics of the molecular cations. This study reveals much more vibrational structural detail in the first electronic excited state of H2CO cations. The first electronic excited state of H2CO cations may have nonplanar equilibrium geometry. Strong isotope effects on vibronic (vibrational) coupling are observed in the second electronic excited state of H2CO. Vibrational autocorrelation functions are calculated for all four observed electronic states of H2CO. The correlation function of the first electronic excited state of H2CO shows a slow decay rate on the femtosecond time scale. The ultrafast decay of the H2CO cations in the third electronic excited state implies that dissociation and intramolecular processes are the main decay pathways. The present spectra of the ground states of ketene cations have more fine structure than before. The AIEs of the first and fifth excited states are determined unambiguously more accurately. The doublet-like fine structures present in the lint excited state of ketene implies the excitation of a soft'' mode not observed before. The vibrational autocorrelation functions are calculated for 4 of the 6 observed electronic states. The dynamics of the ground states of the cations are characterized by a wave packet oscillating with small amplitude around the minimum on the upper PES. The decay dynamics of the first and the fifth excited states of ketene are characterized by ultra-fast intramolecular processes like predissociation.

  5. High resolution photoelectron spectroscopy and femtosecond intramolecular dynamics using supersonic molecular beams

    Energy Technology Data Exchange (ETDEWEB)

    Niu, B.

    1992-09-01

    High resolution He I{alpha} photoelectron spectroscopy of formaldehyde and ketene and their deuterated compounds, are reported. The combination of a (H2CO) double-pass high-resolution electron-energy analyzer and effective rotational cooling of the sample by supersonic expansion enable the spectroscopy of these molecular cations. The vibrational autocorrelation functions are calculated from the high-resolution photoelectron spectra, shedding light on the ultrafast intramolecular dynamics of the molecular cations. This study reveals much more vibrational structural detail in the first electronic excited state of H2CO cations. The first electronic excited state of H2CO cations may have nonplanar equilibrium geometry. Strong isotope effects on vibronic (vibrational) coupling are observed in the second electronic excited state of H2CO. Vibrational autocorrelation functions are calculated for all four observed electronic states of H2CO. The correlation function of the first electronic excited state of H2CO shows a slow decay rate on the femtosecond time scale. The ultrafast decay of the H2CO cations in the third electronic excited state implies that dissociation and intramolecular processes are the main decay pathways. The present spectra of the ground states of ketene cations have more fine structure than before. The AIEs of the first and fifth excited states are determined unambiguously more accurately. The doublet-like fine structures present in the lint excited state of ketene implies the excitation of a ``soft`` mode not observed before. The vibrational autocorrelation functions are calculated for 4 of the 6 observed electronic states. The dynamics of the ground states of the cations are characterized by a wave packet oscillating with small amplitude around the minimum on the upper PES. The decay dynamics of the first and the fifth excited states of ketene are characterized by ultra-fast intramolecular processes like predissociation.

  6. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, D.W.

    1994-08-01

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O{sub 3}{sup {minus}}. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO{sub 2}, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO{sub 2} molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO{sub 2} reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C{sub 2}{sup {minus}} {minus} C{sub 11}{sup {minus}}), and van der Waals clusters (X{sup {minus}}(CO{sub 2}){sub n}, X = I, Br, Cl; n {le} 13 and I{sup {minus}} (N{sub 2}O){sub n=1--11}). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X{sup {minus}}(CO{sub 2})n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products.

  7. Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

  8. Fundamentals of attosecond optics

    CERN Document Server

    Chang, Zenghu

    2011-01-01

    Attosecond optical pulse generation, along with the related process of high-order harmonic generation, is redefining ultrafast physics and chemistry. A practical understanding of attosecond optics requires significant background information and foundational theory to make full use of these cutting-edge lasers and advance the technology toward the next generation of ultrafast lasers. Fundamentals of Attosecond Optics provides the first focused introduction to the field. The author presents the underlying concepts and techniques required to enter the field, as well as recent research advances th

  9. Advances in attosecond science

    Science.gov (United States)

    Calegari, Francesca; Sansone, Giuseppe; Stagira, Salvatore; Vozzi, Caterina; Nisoli, Mauro

    2016-03-01

    Attosecond science offers formidable tools for the investigation of electronic processes at the heart of important physical processes in atomic, molecular and solid-state physics. In the last 15 years impressive advances have been obtained from both the experimental and theoretical points of view. Attosecond pulses, in the form of isolated pulses or of trains of pulses, are now routinely available in various laboratories. In this review recent advances in attosecond science are reported and important applications are discussed. After a brief presentation of various techniques that can be employed for the generation and diagnosis of sub-femtosecond pulses, various applications are reported in atomic, molecular and condensed-matter physics.

  10. UV-Raman spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption studies of model and bulk heterogeneous catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Tewell, Craig R.

    2002-08-19

    X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (TPD) have been used to investigate the surface structure of model heterogeneous catalysts in ultra-high vacuum (UHV). UV-Raman spectroscopy has been used to probe the structure of bulk model catalysts in ambient and reaction conditions. The structural information obtained through UV-Raman spectroscopy has been correlated with both the UHV surface analysis and reaction results. The present day propylene and ethylene polymerization catalysts (Ziegler-Natta catalysts) are prepared by deposition of TiCl{sub 4} and a Al(Et){sub 3} co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl{sub 2} and ethanol. A model thin film catalyst is prepared by depositing metallic Mg on a Au foil in a UHV chamber in a background of TiCl{sub 4} in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl{sub 2} by TiCl{sub 4} resulting in a thin film of MgCl{sub 2}/TiCl{sub x}, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl{sub 2}/TiCl{sub x} on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to {approx}1 Torr of Al(Et){sub 3}.

  11. UV-Raman spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption studies of model and bulk heterogeneous catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Tewell, Craig Richmond [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (TPD) have been used to investigate the surface structure of model heterogeneous catalysts in ultra-high vacuum (UHV). UV-Raman spectroscopy has been used to probe the structure of bulk model catalysts in ambient and reaction conditions. The structural information obtained through UV-Raman spectroscopy has been correlated with both the UHV surface analysis and reaction results. The present day propylene and ethylene polymerization catalysts (Ziegler-Natta catalysts) are prepared by deposition of TiCl4 and a Al(Et)3 co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl2 and ethanol. A model thin film catalyst is prepared by depositing metallic Mg on a Au foil in a UHV chamber in a background of TiCl4 in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl2 by TiCl4 resulting in a thin film of MgCl2/TiClx, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl2/TiClx on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to ~1 Torr of Al(Et)3.

  12. Electronic structure simulation of chromium aluminum oxynitride by discrete variational-X alpha method and X-ray photoelectron spectroscopy

    CERN Document Server

    Choi, Y; Lee, J D; Kim, E; No, K

    2002-01-01

    We use a first-principles discrete variational (DV)-X alpha method to investigate the electronic structure of chromium aluminum oxynitride. When nitrogen is substituted for oxygen in the Cr-Al-O system, the N2p level appears in the energy range between O2p and Cr3d levels. Consequently, the valence band of chromium aluminum oxynitride becomes broader and the band gap becomes smaller than that of chromium aluminum oxide, which is consistent with the photoelectron spectra for the valence band using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). We expect that this valence band structure of chromium aluminum oxynitride will modify the transmittance slope which is a requirement for photomask application.

  13. Electronic structure of AlCrN films investigated using various photoelectron spectroscopies and ab initio calculations

    Science.gov (United States)

    Tatemizo, N.; Imada, S.; Miura, Y.; Yamane, H.; Tanaka, K.

    2017-03-01

    The valence band (VB) structures of wurtzite AlCrN (Cr concentration: 0-17.1%), which show optical absorption in the ultraviolet-visible-infrared light region, were investigated via photoelectron yield spectroscopy (PYS), x-ray/ultraviolet photoelectron spectroscopy (XPS/UPS), and ab initio density of states (DOS) calculations. An obvious photoelectron emission threshold was observed ~5.3 eV from the vacuum level for AlCrN, whereas no emission was observed for AlN in the PYS spectra. Comparisons of XPS and UPS VB spectra and the calculated DOS imply that Cr 3d states are formed both at the top of the VB and in the AlN gap. These data suggest that Cr doping could be a viable option to produce new materials with relevant energy band structures for solar photoelectric conversion.

  14. Chemical functionalization of nanodiamond by amino groups: an X-ray photoelectron spectroscopy study.

    Science.gov (United States)

    Dhanak, V R; Butenko, Yu V; Brieva, A C; Coxon, P R; Alves, L; Siller, L

    2012-04-01

    The development of chemical functionalization techniques for diamond nanocrystallites opens up ways with a view to altering their solubility in different solvents, improve interfacial adhesion of nanodiamonds with a composite matrix in new materials, and provide new possibilities for the modification of the electronic properties of nanodiamond crystallites. In this work, we present results on the chemical functionalization of nanodiamonds by amino groups using ammonia as a nitrogenation agent. Nanodiamond material used was formed by the detonation technique with average crystallite sizes of 4-5 nm. The final materials and intermediates products were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Chemical functionalization of nanodiamonds by amino groups could enable the preparation of new nylon nano-composite materials. Presence of surface amino groups could alter pH of nanodiamond colloids towards basic values and improve colloidal stability of nanodiamond suspensions at pH close to 7. This could enable syntheses of new drug delivery systems based on nanodiamonds.

  15. X-ray photoelectron spectroscopy as a probe of rhodium-ligand interaction in ionic liquids

    Science.gov (United States)

    Men, Shuang; Lovelock, Kevin R. J.; Licence, Peter

    2016-02-01

    We use X-ray photoelectron spectroscopy (XPS) to identify the interaction between the rhodium atom and phosphine ligands in six 1-octyl-3-methylimidazolium-based ionic liquids ([C8C1Im][X]). The formation of a mono-phosphine rhodium complex based upon addition of triphenylphosphine (PPh3) is confirmed by XPS in all ionic liquids studied herein. Due to the electron donation effect of the ligand, the rhodium atom becomes more negatively charged and thus exhibits a lower measured binding energy. The influence of the anion basicity on the formation of different types of rhodium complexes is also investigated. By introducing a biphosphine ligand, a chelated diphosphine rhodium complex is formed in ionic liquids with more basic anions and verified by both XPS and Infrared Spectroscopy (IR). The measured Rh 3d binding energies are correlated to the reaction selectivity of a hydroformylation reaction which inspires a method to design a metal catalyst to control the chemical reaction towards desired products in the future.

  16. [Characterization of biochar by X-ray photoelectron spectroscopy and 13C nuclear magnetic resonance].

    Science.gov (United States)

    Xu, Dong-yu; Jin, Jie; Yan, Yu; Han, Lan-fang; Kang, Ming-jie; Wang, Zi-ying; Zhao, Ye; Sun, Ke

    2014-12-01

    The wood (willow branch) and grass (rice straw) materials were pyrolyzed at different temperatures (300, 450 and 600 °C) to obtain the biochars used in the present study. The biochars were characterized using elementary analysis, X-ray photoelectron spectroscopy (XPS) and solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (13C NMR) to illuminate the structure and composition of the biochars which were derived from the different thermal temperatures and biomass. The results showed that the H/C, O/C and (O+N)/C ratios of the biochars decreased with the increase in the pyrolysis temperatures. The surface polarity and ash content of the grass-derived biochars were higher than those of the wood-derived biochars. The minerals of the wood-derived biochars were mainly covered by the organic matter; in contrast, parts of the mineral surfaces of the grass-derived biochars were not covered by organic matter? The 13C NMR of the low temperature-derived biochars revealed a large contribution of aromatic carbon, aliphatic carbon, carboxyl and carbonyl carbon, while the high temperature-derived biochars contained a large amount of aromatic carbon. Moreover, the wood-derived biochars produced at low heat treatment temperatures contained more lignin residues than grass-derived ones, probably due to the existence of high lignin content in the feedstock soures of wood-derived biochars. The results of the study would be useful for environmental application of biochars.

  17. Investigating Surface and Interface Phenomena in LiFeBO3 Electrodes Using Photoelectron Spectroscopy Depth Profiling

    DEFF Research Database (Denmark)

    Maibach, Julia; Younesi, Reza; Schwarzburger, Nele

    2014-01-01

    The formation of surface and interface layers at the electrodes is highly important for the performance and stability of lithium ion batteries. To unravel the surface composition of electrode materials, photoelectron spectroscopy (PES) is highly suitable as it probes chemical surface and interfac...

  18. Electronic structure of fluorinated multiwalled carbon nanotubes studied using x-ray absorption and photoelectron spectroscopy

    Science.gov (United States)

    Brzhezinskaya, M. M.; Muradyan, V. E.; Vinogradov, N. A.; Preobrajenski, A. B.; Gudat, W.; Vinogradov, A. S.

    2009-04-01

    This paper presents the results of combined investigation of the chemical bond formation in fluorinated multiwalled carbon nanotubes (MWCNTs) with different fluorine contents (10-55wt%) and reference compounds (highly oriented pyrolytic graphite crystals and “white” graphite fluoride) using x-ray absorption and photoelectron spectroscopy at C1s and F1s thresholds. Measurements were performed at BESSY II (Berlin, Germany) and MAX-laboratory (Lund, Sweden). The analysis of the soft x-ray absorption and photoelectron spectra points to the formation of covalent chemical bonding between fluorine and carbon atoms in the fluorinated nanotubes. It was established that within the probing depth (˜15nm) of carbon nanotubes, the process of fluorination runs uniformly and does not depend on the fluorine concentration. In this case, fluorine atoms interact with MWCNTs through the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton (phase 1) and this bonding is accompanied by a change in the hybridization of the 2s and 2p valence electron states of the carbon atom from the trigonal (sp2) to tetrahedral (sp3) hybridization and by a large electron transfer between carbon an fluorine atoms. In the MWCNT near-surface region the second fluorine-carbon phase with weak electron transfer is formed; it is located mainly within two or three upper graphene monolayers, and its contribution becomes much poorer as the probing depth of fluorinated multiwalled carbon nanotubes (F-MWCNTs) increases. The defluorination process of F-MWCNTs on thermal annealing has been investigated. The conclusion has been made that F-MWCNT defluorination without destruction of graphene layers is possible.

  19. Capturing interfacial photoelectrochemical dynamics with picosecond time-resolved X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Neppl, Stefan; Shavorskiy, Andrey; Zegkinoglou, Ioannis; Fraund, Matthew; Slaughter, Daniel S; Troy, Tyler; Ziemkiewicz, Michael P; Ahmed, Musahid; Gul, Sheraz; Rude, Bruce; Zhang, Jin Z; Tremsin, Anton S; Glans, Per-Anders; Liu, Yi-Sheng; Wu, Cheng Hao; Guo, Jinghua; Salmeron, Miquel; Bluhm, Hendrik; Gessner, Oliver

    2014-01-01

    Time-resolved core-level spectroscopy using laser pulses to initiate and short X-ray pulses to trace photoinduced processes has the unique potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics in complex systems. Time-domain studies using transient X-ray absorption and emission techniques have proven extremely valuable to investigate electronic and structural dynamics in isolated and solvated molecules. Here, we describe the implementation of a picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS) technique at the Advanced Light Source (ALS) and its application to monitor photoinduced electron dynamics at the technologically pertinent interface formed by N3 dye molecules anchored to nanoporous ZnO. Indications for a dynamical chemical shift of the Ru3d photoemission line originating from the N3 metal centre are observed ∼30 ps after resonant HOMO-LUMO excitation with a visible laser pump pulse. The transient changes in the TRXPS spectra are accompanied by a characteristic surface photovoltage (SPV) response of the ZnO substrate on a pico- to nanosecond time scale. The interplay between the two phenomena is discussed in the context of possible electronic relaxation and recombination pathways that lead to the neutralisation of the transiently oxidised dye after ultrafast electron injection. A detailed account of the experimental technique is given including an analysis of the chemical modification of the nano-structured ZnO substrate during extended periods of solution-based dye sensitisation and its relevance for studies using surface-sensitive spectroscopy techniques.

  20. Electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy study of the corrosion behaviour of galvanized steel and electroplating steel

    Energy Technology Data Exchange (ETDEWEB)

    Lebrini, M., E-mail: mlebrini@yahoo.fr [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF-LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Traisnel, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF-LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Gengembre, L. [Unite de Catalyse et Chimie du solide UMR 8181 Bat C3, USTL, F-59655, Villeneuve d' Ascq Cedex (France); Fontaine, G. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF-LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Lerasle, O.; Genet, N. [TOTAL France, Centre de Recherche de Solaize, Chemin du canal, BP 22, F-69360 Solaize (France)

    2011-02-01

    The efficiency of a formula containing 2-{l_brace}(2-hydroxyethyl)[(4-methyl-1H-1,2,3-benzotriazol-1-yl)methyl] amino{r_brace}ethanol (tolyltriazole) and decanoic acid as corrosion inhibitor for galvanized steel and electroplating steel in aqueous solution have been determined by electrochemical impedance spectroscopy (EIS) techniques. The experimental data obtained from this method show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The corrosion behaviour in the presence of different concentration of decanoic acid (DA) in the formula was also investigated by EIS. Results obtained reveal that, the formula is a good inhibitor for galvanized steel and electroplating steel in aqueous solution, the better performance was obtained in the case of galvanized steel. The ability of the inhibitor to be adsorbed on the surface was dependent on the nature of metal. X-ray photoelectron spectroscopy surface analysis with inhibitor shows that it's chemisorbed at the galvanized and electroplating steel/aqueous solution interface.

  1. Ambient pressure photoelectron spectroscopy: a new tool for surface science and nanotechnology

    Energy Technology Data Exchange (ETDEWEB)

    Salmeron, Miquel; Salmeron, Miquel; Schlogl, Robert

    2008-03-12

    Progress in science often follows or parallels the development of new techniques. The optical microscope helped convert medicine and biology from a speculative activity in old times to today's sophisticated scientific disciplines. The telescope changed the study and interpretation of heavens from mythology to science. X-ray diffraction enabled the flourishing of solid state physics and materials science. The technique object of this review, Ambient Pressure Photoelectron Spectroscopy or APPES for short, has also the potential of producing dramatic changes in the study of liquid and solid surfaces, particularly in areas such as atmospheric, environment and catalysis sciences. APPES adds an important missing element to the host of techniques that give fundamental information, i.e., spectroscopy and microscopy, about surfaces in the presence of gases and vapors, as encountered in industrial catalysis and atmospheric environments. APPES brings electron spectroscopy into the realm of techniques that can be used in practical environments. Decades of surface science in ultra high vacuum (UHV) has shown the power of electron spectroscopy in its various manifestations. Their unique property is the extremely short elastic mean free path of electrons as they travel through condensed matter, of the order of a few atomic distances in the energy range from a few eV to a few thousand eV. As a consequence of this the information obtained by analyzing electrons emitted or scattered from a surface refers to the top first few atomic layers, which is what surface science is all about. Low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), Ultraviolet photoelectron spectroscopy (UPS), and other such techniques have been used for decades and provided some of the most fundamental knowledge about surface crystallography, composition and electronic structure available today. Unfortunately the high interaction cross section of

  2. Unified ab initio treatment of attosecond photoionization and Compton scattering

    Science.gov (United States)

    Yudin, G. L.; Bondar, D. I.; Patchkovskii, S.; Corkum, P. B.; Bandrauk, A. D.

    2009-10-01

    We present a new theoretical approach to attosecond laser-assisted photo- and Compton ionization. Attosecond x-ray absorption and scattering are described by \\hat{\\mathscr{S}}^{(1,2)} -matrices, which are coherent superpositions of 'monochromatic' \\skew{3}\\hat{S}^{(1,2)} -matrices in a laser-modified Furry representation. Besides refining the existing theory of the soft x-ray photoelectron attosecond streak camera and spectral phase interferometry (ASC and ASPI), we formulate a theory of hard x-ray photoelectron and Compton ASC and ASPI. The resulting scheme has a simple structure and leads to closed-form expressions for ionization amplitudes. We investigate Compton electron interference in the separable Coulomb-Volkov continuum with both Coulomb and laser fields treated non-perturbatively. We find that at laser-field intensities below 1013 Wcm-2 normalized Compton lines almost coincide with the lines obtained in the laser-free regime. At higher intensities, attosecond interferences survive integration over electron momenta, and feature prominently in the Compton lines themselves. We define a regime where the electron ground-state density can be measured with controllable accuracy in an attosecond time interval. The new theory provides a firm basis for extracting photo- and Compton electron phases and atomic and molecular wavefunctions from experimental data.

  3. Investigation of coloration of SrLaGaO sub 4 single crystals by X-ray photoelectron spectroscopy

    CERN Document Server

    Novosselov, A; Talik, E; Pajaczkowska, A

    2003-01-01

    An investigation of the X-ray photoelectron spectra of single crystals of SrLaGaO sub 4 grown by the Czochralski method at various oxygen pressures is reported. Light yellow, yellow and red colored crystals were grown at an oxygen pressure lower than about 5x10 sup - sup 4 atm while the green colored crystals were grown at an oxygen pressure higher than 5x10 sup - sup 3 atm. The presence of Ga sup 1 sup + ions for green colored crystals was demonstrated and the existence of interstitial oxygen atoms in the green and red colored crystals was proposed by using X-ray photoelectron spectroscopy.

  4. Electronic states localized at surface defects on Cu(755) studied by angle-resolved ultraviolet photoelectron spectroscopy using synchrotron radiation

    CERN Document Server

    Ogawa, K; Namba, H

    2003-01-01

    'Regularly stepped' and 'defective' surfaces of Cu(755) were prepared by low- and high-temperature annealing, respectively, of a clean specimen. Electronic states on both surfaces were studied by angle-resolved ultraviolet photoelectron spectroscopy using synchrotron radiation. On the defective Cu(755), we found a new photoelectron peak due to surface defects just below the Fermi level. The dispersion profile of the defect state is derived to be almost flat, which demonstrates the localized nature of the defects. High activity to oxygen adsorption of the defect state was revealed. (author)

  5. Photoelectron spectroscopy study on Li substituted NiO using PES beamline installed on Indus-1

    CERN Document Server

    Banerjee, A; Phase, D M; Dasannacharya, B A

    2003-01-01

    Photoelectron spectroscopy beamline based on a toroidal grating monochromator (TGM) is recently commissioned on Indus-1 storage ring. It has been used to carry out valence band photoemission study of Li substituted NiO. In this paper initially a brief description of the beamline components and the experimental station for angle integrated photoemission experiment is presented. The later part of this paper is devoted to studies carried out on Li sub x Ni sub 1 sub - sub x O with x=0.0, 0.35 and 0.5 samples. Thin pellets of polycrystalline samples were used for the measurements reported here. Valence band spectra recorded on polycrystalline Li sub x Ni sub 1 sub - sub x O samples show drastic changes in various features as compared to that of pure NiO. The prominent changes are: (i) change in the relative contributions of Ni-3d and O-2p emissions, (ii) change in the peak position of Ni-3d from the top of the valance band of NiO and (iii) no noticeable change in the Ni satellite peak. These results are evaluated...

  6. Quantitative determination of ligand densities on nanomaterials by X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Torelli, Marco D; Putans, Rebecca A; Tan, Yizheng; Lohse, Samuel E; Murphy, Catherine J; Hamers, Robert J

    2015-01-28

    X-ray photoelectron spectroscopy (XPS) is a nearly universal method for quantitative characterization of both organic and inorganic layers on surfaces. When applied to nanoparticles, the analysis is complicated by the strong curvature of the surface and by the fact that the electron attenuation length can be comparable to the diameter of the nanoparticles, making it necessary to explicitly include the shape of the nanoparticle to achieve quantitative analysis. We describe a combined experimental and computational analysis of XPS data for molecular ligands on gold nanoparticles. The analysis includes scattering in both Au core and organic shells and is valid even for nanoparticles having diameters comparable to the electron attenuation length (EAL). To test this model, we show experimentally how varying particle diameter from 1.3 to 6.3 nm leads to a change in the measured AC/AAu peak area ratio, changing by a factor of 15. By analyzing the data in a simple computational model, we demonstrate that ligand densities can be obtained, and, moreover, that the actual ligand densities for these nanoparticles are a constant value of 3.9 ± 0.2 molecules nm(-2). This model can be easily extended to a wide range of core-shell nanoparticles, providing a simple pathway to extend XPS quantitative analysis to a broader range of nanomaterials.

  7. Photoelectron Spectroscopy of YbInCu{sub 4}: Direct Testing of Correlated Electron Models

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.J.; Arko, A.J.; Sarrao, J.L.; Fisk, Z.

    1997-12-31

    The electronic properties of single crystal YbInCu{sub 4} have been investigated by means of high resolution photoelectron spectroscopy. A first order, isostructural phase transition for YbInCu{sub 4} at T{sub v}=42 K leads to changes in the Kondo temperature of more than an order of magnitude (27 K vs. 400 K). This phase transition and accompanying Kondo temperature change provide the most direct test of the single impurity model (SIM) to date. Particle hole symmetry allows the SIM to be used for Yb compounds as well as Ce heavy fermions with the great advantage that the predicted Kondo resonance is found on the occupied side of the spectral weight function for Yb materials and is thus directly observable in photoemission. The photoemission results are incongruous with the single impurity model predictions for temperature dependence, binding energy and 4f occupancy, encouraging a reevaluation of the single impurity model. The experiments were conducted using the PGM undulator and 4 meter NIM beamlines at SRC. The spectra were taken at photon energies of 40 eV and 90 eV and the combined energy resolution of the analyzer and monochromator was 45- 85 meV.

  8. X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes)

    Science.gov (United States)

    Halim, Joseph; Cook, Kevin M.; Naguib, Michael; Eklund, Per; Gogotsi, Yury; Rosen, Johanna; Barsoum, Michel W.

    2016-01-01

    In this work, a detailed high resolution X-ray photoelectron spectroscopy (XPS) analysis is presented for select MXenes-a recently discovered family of two-dimensional (2D) carbides and carbonitrides. Given their 2D nature, understanding their surface chemistry is paramount. Herein we identify and quantify the surface groups present before, and after, sputter-cleaning as well as freshly prepared vs. aged multi-layered cold pressed discs. The nominal compositions of the MXenes studied here are Ti3C2Tx, Ti2CTx, Ti3CNTx, Nb2CTx and Nb4C3Tx, where T represents surface groups that this work attempts to quantify. In all the cases, the presence of three surface terminations, sbnd O, sbnd OH and sbnd F, in addition to OH-terminations relatively strongly bonded to H2O molecules, was confirmed. From XPS peak fits, it was possible to establish the average sum of the negative charges of the terminations for the aforementioned MXenes. Based on this work, it is now possible to quantify the nature of the surface terminations. This information can, in turn, be used to better design and tailor these novel 2D materials for various applications.

  9. Light-induced atom desorption from glass surfaces characterized by X-ray photoelectron spectroscopy

    Science.gov (United States)

    Kumagai, Ryo; Hatakeyama, Atsushi

    2016-07-01

    We analyzed the surfaces of vitreous silica (quartz) and borosilicate glass (Pyrex) substrates exposed to rubidium (Rb) vapor by X-ray photoelectron spectroscopy (XPS) to understand the surface conditions of alkali metal vapor cells. XPS spectra indicated that Rb atoms adopted different bonding states in quartz and Pyrex. Furthermore, Rb atoms in quartz remained in the near-surface region, while they diffused into the bulk in Pyrex. For these characterized surfaces, we measured light-induced atom desorption (LIAD) of Rb atoms. Clear differences in time evolution, photon energy dependence, and substrate temperature dependence were found; the decay of LIAD by continuous ultraviolet irradiation for quartz was faster than that for Pyrex, a monotonic increase in LIAD with increasing photon energy from 1.8 to 4.3 eV was more prominent for quartz, and LIAD from quartz was more efficient at higher temperatures in the range from 300 to 580 K, while that from Pyrex was almost independent of temperature.

  10. Negative ion photoelectron spectroscopy of the copper-aspartic acid anion and its hydrated complexes

    Science.gov (United States)

    Li, Xiang; Wang, Haopeng; Bowen, Kit H.; Martínez, Ana; Salpin, Jean-Yves; Schermann, Jean-Pierre

    2010-08-01

    Negative ions of copper-aspartic acid Cu(Asp)- and its hydrated complexes have been produced in the gas phase and studied by anion photoelectron spectroscopy. The vertical detachment energies (VDE) of Cu(Asp)- and Cu(Asp)-(H2O)1,2 were determined to be 1.6, 1.95, and 2.20 eV, respectively. The spectral profiles of Cu(Asp)-(H2O)1 and Cu(Asp)-(H2O)2 closely resembled that of Cu(Asp)-, indicating that hydration had not changed the structure of Cu(Asp)- significantly. The successive shifts to higher electron binding energies by the spectra of the hydrated species provided measures of their stepwise solvation energies. Density functional calculations were performed on anionic Cu(Asp)- and on its corresponding neutral. The agreement between the calculated and measured VDE values implied that the structure of the Cu(Asp)- complex originated with a zwitterionic form of aspartic acid in which a copper atom had inserted into the N-H bond.

  11. Effect of Space Radiation Processing on Lunar Soil Surface Chemistry: X-Ray Photoelectron Spectroscopy Studies

    Science.gov (United States)

    Dukes, C.; Loeffler, M.J.; Baragiola, R.; Christoffersen, R.; Keller, J.

    2009-01-01

    Current understanding of the chemistry and microstructure of the surfaces of lunar soil grains is dominated by a reference frame derived mainly from electron microscopy observations [e.g. 1,2]. These studies have shown that the outermost 10-100 nm of grain surfaces in mature lunar soil finest fractions have been modified by the combined effects of solar wind exposure, surface deposition of vapors and accretion of impact melt products [1,2]. These processes produce surface-correlated nanophase Feo, host grain amorphization, formation of surface patinas and other complex changes [1,2]. What is less well understood is how these changes are reflected directly at the surface, defined as the outermost 1-5 atomic monolayers, a region not easily chemically characterized by TEM. We are currently employing X-ray Photoelectron Spectroscopy (XPS) to study the surface chemistry of lunar soil samples that have been previously studied by TEM. This work includes modification of the grain surfaces by in situ irradiation with ions at solar wind energies to better understand how irradiated surfaces in lunar grains change their chemistry once exposed to ambient conditions on earth.

  12. X-ray photoelectron spectroscopy studies on core-shell structured nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, M. [Surface Physics Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Basu, S.; Ghosh, B. [Unit on Nano Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Chakravorty, D. [Unit on Nano Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)], E-mail: mlsdc@iacs.res.in

    2007-08-15

    Core-shell nanostructures were grown in silica-based glasses. Copper-copper oxide and iron-iron oxide structures had diameters in the range 3-6 nm, with shell thicknesses {approx}1-2 nm. Silver-lithium niobate core-shell nanostructures had diameters in the range 4.2-46 nm and thicknesses varying from 2.2 to 22 nm. X-ray photoelectron spectroscopy studies were carried out on all these specimens. The analyses of these results show the presence of Cu{sup +}/Cu{sup 2+}, Fe{sup 2+}/Fe{sup 3+} and Nb{sup 4+}/Nb{sup 5+} valence states in the above three systems. Electrical resistivity data were fitted satisfactorily to the small polaron hopping model in the case of copper and iron-containing specimens. The presence of ions in the lithium niobate shell provides direct evidence of the formation of localized states between which variable range hopping conduction can be effected.

  13. Chemistry of carbon polymer composite electrode - An X-ray photoelectron spectroscopy study

    Science.gov (United States)

    Andersen, Shuang Ma; Dhiman, Rajnish; Skou, Eivind

    2015-01-01

    Surface chemistry of the electrodes in a proton exchange membrane fuel cell is of great importance for the cell performance. Many groups have reported that electrode preparation condition has a direct influence on the resulting electrode properties. In this work, the oxidation state of electrode components and the composites (catalyst ionomer mixtures) in various electrode structures were systematically studied with X-ray photoelectron spectroscopy (XPS). Based on the spectra, when catalyst is physically mixed with Nafion ionomer, the resulting electrode surface chemistry is a combination of the two components. When the electrode is prepared with a lamination procedure, the ratio between fluorocarbon and graphitic carbon is decreased. Moreover, ether type oxide content is decreased although carbon oxide is slightly increased. This indicates structure change of the catalyst layer due to an interaction between the ionomer and the catalyst and possible polymer structural change during electrode fabrication. The surface of micro porous layer was found to be much more influenced by the lamination, especially when it is in contact with catalysts in the interphase. Higher amount of platinum oxide was observed in the electrode structures (catalyst ionomer mixture) compared to the catalyst powder. This also indicates a certain interaction between the functional groups in the polymer and platinum surface.

  14. Characterization of peptide attachment on silicon nanowires by X-ray photoelectron spectroscopy and mass spectrometry.

    Science.gov (United States)

    Kurylo, Ievgen; Dupré, Mathieu; Cantel, Sonia; Enjalbal, Christine; Drobecq, Hervé; Szunerits, Sabine; Melnyk, Oleg; Boukherroub, Rabah; Coffinier, Yannick

    2017-02-27

    In this paper, we report an original method to immobilize a model peptide on silicon nanowires (SiNWs) via a photolinker attached to the SiNWs' surface. The silicon nanowires were fabricated by a metal assisted chemical etching (MACE) method. Then, direct characterization of the peptide immobilization on SiNWs was performed either by X-ray photoelectron spectroscopy (XPS) or by laser-desorption/ionization mass spectrometry (LDI-MS). XPS allowed us to follow the peptide immobilization and its photorelease by recording the variation of the signal intensities of the different elements present on the SiNW surface. Mass spectrometry was performed without the use of an organic matrix and peptide ions were produced via a photocleavage mechanism. Indeed, thanks to direct photorelease achieved upon laser irradiation, a recorded predictable peak related to the molecular peptide ion has been detected, allowing the identification of the model peptide. Additional MS/MS experiments confirmed the photodissociation site and confirmed the N-terminal immobilization of the peptide on SiNWs.

  15. Structures of cycloserine and 2-oxazolidinone probed by X-ray photoelectron spectroscopy: theory and experiment.

    Science.gov (United States)

    Ahmed, Marawan; Wang, Feng; Acres, Robert G; Prince, Kevin C

    2014-05-22

    The electronic structures and properties of 2-oxazolidinone and the related compound cycloserine (CS) have been investigated using theoretical calculations and core and valence photoelectron spectroscopy. Isomerization of the central oxazolidine heterocycle and the addition of an amino group yield cycloserine. Theory correctly predicts the C, N, and O 1s core spectra, and additionally, we report theoretical natural bond orbital (NBO) charges. The valence ionization energies are also in agreement with theory and previous measurements. Although the lowest binding energy part of the spectra of the two compounds shows superficial similarities, further analysis of the charge densities of the frontier orbitals indicates substantial reorganization of the wave functions as a result of isomerization. The highest occupied molecular orbital (HOMO) of CS shows leading carbonyl π character with contributions from other heavy (non-H) atoms in the molecule, while the HOMO of 2-oxazolidinone (OX2) has leading nitrogen, carbon, and oxygen pπ characters. The present study further theoretically predicts bond resonance effects of the compounds, evidence for which is provided by our experimental measurements and published crystallographic data.

  16. X-ray photoelectron spectroscopy for characterization of bionanocomposite functional materials for energy-harvesting technologies.

    Science.gov (United States)

    Artyushkova, Kateryna; Atanassov, Plamen

    2013-07-22

    The analysis of hybrid multicomponent bioorganic and bioinorganic composite materials related to energy technologies by using X-ray photoelectron spectroscopy is discussed. The approaches and considerations of overcoming the difficulties of analyzing hybrid multicomponent materials are demonstrated for different types of materials used in bioenzyme fuel cells, that is, enzyme immobilization in a hybrid inorganic-organic matrix, analysis of peptide binding and structure in the mediation of silica nanoparticle formation, analysis of enzyme-polymeric multilayered architectures obtained through layer-by-layer assembly, and study of the mechanism of electropolymerization. Thorough optimization of experimental design through analysis of an adequate set of reference materials, relevant timescales of sample preparation and X-ray exposure, careful peak decomposition and cross-correlation between elemental speciation, results in a detailed understanding of the chemistry of nanocomposite constituents and interactions between them. The methodology presented and examples discussed are of significant importance to the scientific and engineering communities focused on the immobilization of enzymes, proteins, peptides, and other large biological molecules on solid substrates.

  17. Initial processes of proton transfer in salicylideneaniline studied by time-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Sekikawa, Taro; Schalk, Oliver; Wu, Guorong; Boguslavskiy, Andrey E; Stolow, Albert

    2013-04-11

    Excited-state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) and selected derivatives substituted in the para position of the anilino group have been investigated by femtosecond time-resolved photoelectron spectroscopy (TRPES) and time-dependent density functional theory (TDDFT). SA has a twisted structure at the energetic minimum of the ground state, but ESIPT is assumed to take place through a planar structure, although this has not been fully established. The TRPES studies revealed that the excited-state dynamics within the S1 band varied significantly with excitation wavelength. At finite temperatures, the ground state was found to sample a broad range of torsional angles, from planar to twisted. At lower photon energies (370 nm), only the planar ground-state molecules were excited, and the excited-state reaction took place within 50 fs. At higher energies (350 and 330 nm), predominantly twisted ground-state molecules were excited: they had to planarize before ESIPT could occur. This process was found to be slower in methylated SA but did not change significantly in the brominated and nitrated SAs. These substitution effects on the decay dynamics can be explained by modifications of the potential barriers, as predicted by the TDDFT calculations, and support the mechanism of a twisting motion of the anilino ring prior to ESIPT. The contribution of another pathway leading to internal conversion within the enol form was found to be minor at the excitation wavelengths considered here.

  18. CHARACTERIZING SURFACE LAYERS IN NITINOL USING X-RAY PHOTOELECTRON SPECTROSCOPY

    Energy Technology Data Exchange (ETDEWEB)

    Christopfel, R.; Mehta, A.

    2008-01-01

    Nitinol is a shape memory alloy whose properties allow for large reversible deformations and a return to its original geometry. This nickel-titanium (NiTi) alloy has become a material used widely in the biomedical fi eld as a stent to open up collapsed arteries. Both ambient and biological conditions cause surface oxidation in these devices which in turn change its biocompatibility. The thickness of oxidized layers can cause fractures in the material if too large and can allow for penetration if too thin. Depending on the type and abundance of the chemical species on or near the surface, highly toxic metal ions can leak into the body causing cell damage or even cell death. Thus, biocompatibility of such devices is crucial. By using highly surface sensitive x-ray photoelectron spectroscopy to probe the surface of these structures, it is possible to decipher both layer composition and layer thickness. Two samples, both of which were mechanically polished, were investigated. Of the two samples, one was then exposed to a phosphate buffered saline (PBS) solution to mimic the chemical properties of blood, while the other remained unexposed. Although both samples were found to have oxide layers of appropriate thickness (on the order of a few nm), it was found that the sample exposed to the saline solution had a slightly thicker oxide layer and more signifi cantly, a phosphate layer very near the surface suggesting toxic metal components are well contained within the sample. These are considerable indications of a biocompatible device.

  19. Recent progress of soft X-ray photoelectron spectroscopy studies of uranium compounds

    Energy Technology Data Exchange (ETDEWEB)

    Fujimori, Shin-ichi; Takeda, Yukiharu; Okane, Tetsuo; Saitoh, Yuji [Condensed Matter Science Divisions, Japan Atomic Energy Agency, Sayo, Hyogo (Japan); Fujimori, Atsushi [Condensed Matter Science Divisions, Japan Atomic Energy Agency, Sayo, Hyogo (Japan); Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Yamagami, Hiroshi [Condensed Matter Science Divisions, Japan Atomic Energy Agency, Sayo, Hyogo (Japan); Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555 (Japan); Yamamoto, Etsuji; Haga, Yoshinori [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Ōnuki, Yoshichika [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213 (Japan)

    2016-04-15

    Recent progresses in the soft X-ray photoelectron spectroscopy (PES) studies (hν ≳ 100 eV) for uranium compounds are briefly reviewed. The soft X-ray PES has enhanced sensitivities for the bulk U 5f electronic structure, which is essential to understand the unique physical properties of uranium compounds. In particular, the recent remarkable improvement in energy resolutions from an order of 1 eV to 100 meV made it possible to observe fine structures in U 5f density of states. Furthermore, soft X-ray ARPES becomes available due to the increase of photon flux at beamlines in third generation synchrotron radiation facilities.The technique made it possible to observe bulk band structures and Fermi surfaces of uranium compounds and therefore, the results can be directly compared with theoretical models such as band-structure calculations. The core-level spectra of uranium compounds show a systematic behavior depending on their electronic structures, suggesting that they can be utilized to determine basic physical parameters such as the U 5f-ligand hybridizations or Comlomb interaction between U 5f electrons. It is shown that soft X-ray PES provides unique opportunities to understand the electronic structures of uranium compounds.

  20. Near surface composition of some alloys by X-ray photoelectron spectroscopy

    Indian Academy of Sciences (India)

    M Sreemany; T B Ghosh

    2001-10-01

    Chemical compositions of the alloys of CuNi (Cu0.10Ni0.90, Cu0.30Ni0.70, Cu0.70Ni0.30) and BiSb (Bi0.80Sb0.20, Bi0.64Sb0.34, Bi0.55Sb0.45) are determined by X-ray photoelectron spectroscopy. The stoichiometries are determined and are compared with the bulk compositions. Possible sources of systematic errors contributing to the results are discussed. Errors arising out of preferential etching in these alloys have been investigated. It has been inferred from such studies that the preferential etching does not enrich the surface composition with a particular component for the two systems reported here. Quantitative results of CuNi system indicate that the surface regions of the Cu0.70Ni0.30 alloy is Cu-rich, although no such evidence is observed in case of BiSb system.

  1. Hydrazine reduction of transition metal oxides - In situ characterization using X-ray photoelectron spectroscopy

    Science.gov (United States)

    Littrell, D. M.; Tatarchuk, B. J.

    1986-01-01

    The transition metal oxides (TMOs) V2O5, FeO3, Co3O4, NiO, CuO, and ZnO were exposed to hydrazine at various pressures. The metallic surfaces were surveyed by in situ X-ray photoelectron spectroscopy to determine the irrelative rate of reduction by hydrazine. The most easily reducible oxide, CuO, could be reduced to the metallic state at room temperature and 10 to the -6th torr. The reaction is first order with respect to CuO, with an activation energy of about 35 kJ/mol. Two types of adsorption were seen to occur at 295 K: (1) a reversible component in which the measured N:Cu ratio increased to 0.60 at hydrazine pressures up to 0.5 torr, and (2) an irreversible component, with a N:Cu ratio of 0.28, which could not be removed by extended vacuum pumping. The results of this study are useful for the identification of TMO's that can be used as solid neatallizers of hydrazine spills, and for the preparation of metal surfaces for electroplating and evaporative thin-film coating.

  2. X-ray photoelectron spectroscopy for wheat powders: measurement of surface chemical composition.

    Science.gov (United States)

    Saad, Moustafa; Gaiani, Claire; Mullet, Martine; Scher, Joel; Cuq, Bernard

    2011-03-09

    The functional properties of wheat powders depend largely on the surface characteristics of their particles. X-ray photoelectron spectroscopy (XPS) has been considered to investigate the surface composition of wheat powders. The objective of the present study is to evaluate the ability of XPS to discriminate wheat components and to calculate the surface composition of wheat powders. First, XPS surveys for the main wheat isolated components (starch, proteins, arabinoxylans, and lipids) were determined. XPS results demonstrate that it is able to distinguish wheat proteins, polysaccharides, and lipids, but it is not able to distinguish starch and arabinoxylan because of their similarity in chemical structure. The XPS analyses of simple reconstituted wheat flours based on two components (starch and protein) or three components (by adding arabinoxylan) demonstrated the ability of XPS to measure the surface composition of the wheat flours. The surface composition of native wheat flour demonstrated an overrepresentation of protein (54%) and lipids (44%) and an underrepresentation of starch (2%) compared to the bulk composition. Results are discussed with regard to difficulties in discriminating arabinoxylans and starch components.

  3. Photoelectron spectroscopy and density functional theory studies of N-rich energetic materials

    Science.gov (United States)

    Zeng, Zhen; Bernstein, Elliot R.

    2016-10-01

    The geometric and electronic structures of molecular anionic energetic materials (EMs) DAAF (3,3'-diamino-4,4'-azoxyfurazan), FOX-7 (1,1-diamino-2,2-dinitroethene), 5,5'-BT (5,5'-bistetrazole), and 1,5'-BT (1,5'-bistetrazole) are explored employing anionic photoelectron spectroscopy and density functional theory calculations. The electron binding energies of the observed anionic, energetic material related species are determined and their corresponding anionic structures are assigned. Decomposition reactions for negatively charged EMs can proceed with different energy barriers, and thus mechanisms, from those for their related neutral EMs. Reactivity based on the anionic initial fragments of these EM species further reinforces their respective highly reactive and explosive nature. Fragment ions of the form EM--H-X (X = N2, N2+NH, …) are additionally observed. Detection of such species suggests that EM--H could serve as promising new candidates for EMs, assuming that such species are synthetically available, perhaps as energetic salts. Vertical detachment energies for transitions to the ground and first triplet electronic excited states of neutral matrix dye anion DCM- are additionally determined.

  4. Cluster Model Studies of Anion and Molecular Specificities via Electrospray Ionization Photoelectron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue-Bin

    2017-01-30

    Ion specificity, a widely observed macroscopic phenomenon in condensed phases and at interfaces, is essentially a fundamental chemical physical issue. We have been investigating such effects using cluster models in an “atom-by-atom” and “molecule-by-molecule” fashion not possible with condensed-phase methods. We use electrospray ionization (ESI) to generate molecular and ionic clusters to simulate key molecular entities involved in local binding regions, and characterize them employing negative ion photoelectron spectroscopy (NIPES). Inter- and intramolecular interactions and binding configurations are directly obtained as functions of cluster size and composition, providing insightful molecular-level description and characterization over the local active sites that play crucial roles in determining solution chemistry and condensed phase phenomena. The topics covered in this article are relevant to a wide scope of research fields ranging from ion specific effects in electrolyte solutions, ion selectivity/recognition in normal functioning of life, to molecular specificity in aerosol particle formation, as well as in rational material design and synthesis.

  5. Growth and structure of thin platinum films deposited on Co(0001) studied by low-energy electron diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and scanning tunneling microscopy

    Science.gov (United States)

    Cabeza, G. F.; Légaré, P.; Sadki, A.; Castellani, N. J.

    2000-06-01

    The growth of platinum deposited on Co(0001) at room temperature in the range of submonolayer coverage is described. The evolution of very thin Pt films has been studied using low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and scanning tunneling microscopy (STM). The LEED patterns suggested a coherent epitaxial growth mode for Pt on Co(0001). Evidence for an island growth mode has been confirmed by STM together with step decoration. However, the second and third monolayers start growing before the completion of the first Pt layer. The electronic structure of the Pt deposits exhibited original properties with low Fermi level density of states and valence-band broadening. This is in agreement with theoretical calculations presented in this work.

  6. Photoelectron Spectroscopy Study of [Ta2B6]-: a Hexagonal Bipyramdial Cluster

    Science.gov (United States)

    Jian, Tian; Li, Weili; Romanescu, Constantin; Wang, Lai-Sheng

    2014-06-01

    It has been a long-sought goal in cluster science to discover stable atomic clusters as building blocks for cluster-assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses.[1,2] Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid-state chemistry.[3] Herein we report a joint photoelectron spectroscopy and theoretical study on the [Ta2B6]- and [Ta2B6] clusters.[4] The photoelectron spectrum of [Ta2B6]- displays a simple spectral pattern and a large HOMO-LUMO gap, suggesting its high symmetry. Theoretical calculations show that both the neutral and anion are D6h pyramidal. The chemical bonding analyses for [Ta2B6] revealed the nature of the B6 and Ta interactions and uncovered strong covalent bonding between B6 and Ta. The D6h-[TaB6Ta] gaseous cluster is reminiscent of the structural pattern in the ReB6X6Re core in the [(Cp*Re)2B6H4Cl2] and the TiB6Ti motif in the newly synthesized Ti7Rh4Ir2B8 solid-state compound.[5,6] The current work provides an intrinsic link between a gaseous cluster and motifs for solid materials. Continued investigations of the transition-metal boron clusters may lead to the discovery of new structural motifs involving pure boron clusters for the design of novel boride materials. Reference [1] H.W. Kroto, J. R. Heath, S. C. OBrien, R. F. Curl, R. E. Smalley, Nature 1985, 318, 162 - 163. [2] W. Krtschmer, L. D. Lamb, K. Fostiropoulos, D. R. Huffman, Nature 1990, 347, 354 - 358. [3] T. P. Fehlner, J.-F. Halet, J.-Y. Saillard, Molecular Clusters: A Bridge to Solid-State Chemitry, Cambridge University Press, UK, 2007. [4] W. L. Li, L. Xie, T. Jian, C. Romanescu, X. Huang, L.-S. Wang, Angew. Chem. Int. Ed. 2014, 126, 1312 - 1316. [5] B. Le Guennic, H. Jiao, S. Kahlal, J.-Y. Saillard, J.-F. Halet, S. Ghosh, M. Shang, A. M. Beatty, A. L. Rheingold, T. P. Fehlner, J. Am. Chem. Soc. 2004, 126, 3203 - 3217. [6] B. P. T. Fokwa, M. Hermus, Angew

  7. Photoelectron imaging spectroscopy of MoC{sup −} and NbN{sup −} diatomic anions: A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qing-Yu; Li, Zi-Yu; He, Sheng-Gui, E-mail: shengguihe@iccas.ac.cn, E-mail: chenh@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Hu, Lianrui; Chen, Hui, E-mail: shengguihe@iccas.ac.cn, E-mail: chenh@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Ning, Chuan-Gang [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Ma, Jia-Bi [Key Laboratory of Cluster Science, The Institute for Chemical Physics, School of Chemistry, Beijing Institute of Technology, Beijing 100081 (China)

    2015-04-28

    The isoeletronic diatomic MoC{sup −} and NbN{sup −} anions have been prepared by laser ablation and studied by photoelectron imaging spectroscopy combined with quantum chemistry calculations. The photoelectron spectra of NbN{sup −} can be very well assigned on the basis of literature reported optical spectroscopy of NbN. In contrast, the photoelectron spectra of MoC{sup −} are rather complex and the assignments suffered from the presence of many electronically hot bands and limited information from the reported optical spectroscopy of MoC. The electron affinities of NbN and MoC have been determined to be 1.450 ± 0.003 eV and 1.360  ±  0.003 eV, respectively. The good resolution of the imaging spectroscopy provided a chance to resolve the Ω splittings of the X{sup 3}Σ{sup −} (Ω = 0 and 1) state of MoC and the X{sup 4}Σ{sup −} (Ω = 1/2 and 3/2) state of MoC{sup −} for the first time. The spin-orbit splittings of the X{sup 2}Δ state of NbN{sup −} and the a{sup 2}Δ state of MoC{sup −} were also determined. The similarities and differences between the electronic structures of the NbN and MoC systems were discussed.

  8. Broadband multilayer soft X-ray mirrors for attosecond pulse formation at photon energies above 100 eV

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, Michael; Schuster, Joerg; Kleineberg, Ulf [LMU, Physik (Germany); Aquila, Andrew [CXRO (United States); Schulze, Martin; Fiess, Markus; Gouliemakis, Eleftherios; Krausz, Ferenc [MPQ (Germany); Huth, Martin [LMU, Chemie (Germany)

    2009-07-01

    We report on the development, fabrication and application of multilayer mirrors as broadband soft-X-ray optical components for the formation of attosecond (1 asec=10{sup -18}s)pulses from high harmonic radiation. Until recently, attosecond physics was merely confined to the photon energy range below 100 eV due to the properties of Mo/Si multilayer and single isolated pulses of 80 asec pulse duration have been achieved. For many applications, e.g. in the characterization of the photoemission dynamics from solid surfaces or the characterization of ultrafast surface plasmon dynamics in metallic nanostructures by attosecond pump-probe spectroscopy, higher photon energies are desirable to address deeper bound electronic core states or to increase the kinetic energy of the emitted photoelectrons. Here, we introduce new aperiodic broad bandwidth multilayer systems based on lanthanum (e.g. LaMo, LaB{sub 4}CMo, LaB{sub 4}C, MoB{sub 4}C),for the 100-190 eV photon energy range. Multilayer properties like interface roughness, interlayer formation and reflectivity are discussed. Finally, first applications for spectral filtering of the HHG comb above 100 eV are presented.

  9. Study of organic radicals through anion photoelectron velocity-map imaging spectroscopy

    Science.gov (United States)

    Dixon, Andrew Robert

    .30(4) eV. The EA of methylglyoxal is determined as ≤ 0.8 eV based on the signal-to-noise ratio of the X 1A ' ← X 2A'' transition, with a VDE = 1.28(4) eV. The EA of the a 3A'' ← X 2A '' and A 1A'' ← X 2A'' transitions are determined as 3.28(3) eV and 3.614(5) eV respectively. The intrinsically short-lived ethylenedione molecule (OCCO) was observed and investigated using anion photoelectron spectroscopy. The adiabatic electron affinity of its 3Sigmag □ ground state is 1.936(8) eV. The vibrational progression with a 417(15) cm-1 frequency observed within the triplet band corresponds to a trans-bending mode. Several dissociative singlet states are also observed, corresponding to two components of the 1Delta g state and the 1Sigmag + state. The experimental results are in agreement with the theory predictions and constitute the first spectroscopic observation and characterization of the elusive ethylenedione molecule. Two glyoxal derivatives related to the ethylenedione anion (OCCO -), ethynediolide (HOCCO-) and glyoxalide (OHCCO-), were studied. These anions provide access to the corresponding neutral reactive intermediates: the HOCCO and OHCCO radicals. In the HOCCO/OHCCO anion photoelectron spectrum, we identify several electronic states of this radical system and determine the adiabatic electron affinity of HOCCO as 1.763(6) eV. This result is compared to the corresponding 1.936(8) eV value for ethylenedione (OCCO). Initial attempts were made to detect and observe the dicyanoacetylene anion, NCCCCN- , by photoelectron imaging. While it is believed the experimental design path of H2+ abstraction from fumaronitrile is sound, no spectral signature can be assigned to NCCCCN -. Calculations targeting the low-lying transitions from the anion indicate that the molecule should have a significantly positive electron affinity and at least the ground state should be accessible with the currently available laser sources. The cluster ion O2(N2O) of the same nominal mass as

  10. Synchrotron-based double imaging photoelectron/photoion coincidence spectroscopy of radicals produced in a flow tube: OH and OD

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Gustavo A.; Tang, Xiaofeng; Gil, Jean-François; Nahon, Laurent [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette (France); Ward, Michael; Batut, Sebastien; Fittschen, Christa [PC2A, Université de Lille 1, UMR CNRS-USTL 8522, Cité Scientifique Bât. C11, F-59655 Villeneuve d’Ascq (France); Taatjes, Craig A.; Osborn, David L. [Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969 (United States); Loison, Jean-Christophe [ISM, Université Bordeaux 1, CNRS, 351 cours de la Libération, 33405 Talence Cedex (France)

    2015-04-28

    We present a microwave discharge flow tube coupled with a double imaging electron/ion coincidence device and vacuum ultraviolet (VUV) synchrotron radiation. The system has been applied to the study of the photoelectron spectroscopy of the well-known radicals OH and OD. The coincidence imaging scheme provides a high selectivity and yields the spectra of the pure radicals, removing the ever-present contributions from excess reactants, background, or secondary products, and therefore obviating the need for a prior knowledge of all possible byproducts. The photoelectron spectra encompassing the X{sup 3}Σ{sup −} ground state of the OH{sup +} and OD{sup +} cations have been extracted and the vibrational constants compared satisfactorily to existing literature values. Future advantages of this approach include measurement of high resolution VUV spectroscopy of radicals, their absolute photoionization cross section, and species/isomer identification in chemical reactions as a function of time.

  11. Synchrotron-based double imaging photoelectron/photoion coincidence spectroscopy of radicals produced in a flow tube: OH and OD

    Science.gov (United States)

    Garcia, Gustavo A.; Tang, Xiaofeng; Gil, Jean-François; Nahon, Laurent; Ward, Michael; Batut, Sebastien; Fittschen, Christa; Taatjes, Craig A.; Osborn, David L.; Loison, Jean-Christophe

    2015-04-01

    We present a microwave discharge flow tube coupled with a double imaging electron/ion coincidence device and vacuum ultraviolet (VUV) synchrotron radiation. The system has been applied to the study of the photoelectron spectroscopy of the well-known radicals OH and OD. The coincidence imaging scheme provides a high selectivity and yields the spectra of the pure radicals, removing the ever-present contributions from excess reactants, background, or secondary products, and therefore obviating the need for a prior knowledge of all possible byproducts. The photoelectron spectra encompassing the X3Σ- ground state of the OH+ and OD+ cations have been extracted and the vibrational constants compared satisfactorily to existing literature values. Future advantages of this approach include measurement of high resolution VUV spectroscopy of radicals, their absolute photoionization cross section, and species/isomer identification in chemical reactions as a function of time.

  12. Hard X-ray photoelectron spectroscopy of bulk and thin films of Heusler compounds

    Energy Technology Data Exchange (ETDEWEB)

    Kozina, Xeniya

    2012-03-26

    X-ray photoemission spectroscopy (XPS) is one of the most universal and powerful tools for investigation of chemical states and electronic structures of materials. The application of hard X-rays increases the inelastic mean free path of the emitted electrons within the solid and thus makes hard X-ray photoelectron spectroscopy (HAXPES) a bulk sensitive probe for solid state research and especially a very effective nondestructive technique to study buried layers. This thesis focuses on the investigation of multilayer structures, used in magnetic tunnel junctions (MTJs), by a number of techniques applying HAXPES. MTJs are the most important components of novel nanoscale devices employed in spintronics. The investigation and deep understanding of the mechanisms responsible for the high performance of such devices and properties of employed magnetic materials that are, in turn, defined by their electronic structure becomes feasible applying HAXPES. Thus the process of B diffusion in CoFeB-based MTJs was investigated with respect to the annealing temperature and its influence on the changes in the electronic structure of CoFeB electrodes that clarify the behaviour and huge TMR ratio values obtained in such devices. These results are presented in chapter 6. The results of investigation of the changes in the valence states of buried off-stoichiometric Co{sub 2}MnSi electrodes were investigated with respect to the Mn content {alpha} and its influence on the observed TMR ratio are described in chapter 7. Magnetoelectronic properties such as exchange splitting in ferromagnetic materials as well as the macroscopic magnetic ordering can be studied by magnetic circular dichroism in photoemission (MCDAD). It is characterized by the appearance of an asymmetry in the photoemission spectra taken either from the magnetized sample with the reversal of the photon helicity or by reversal of magnetization direction of the sample when the photon helicity direction is fixed. Though

  13. Assessment of Quantum Mechanical Methods for Copper and Iron Complexes by Photoelectron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Shuqiang; Huang, Dao-Ling; Dau, Phuong D.; Liu, Hong-Tao; Wang, Lai S.; Ichiye, Toshiko

    2014-03-11

    Broken-symmetry density functional theory (BS-DFT) calculations are assessed for redox energetics [Cu(SCH3)2]1–/0, [Cu(NCS)2]1–/0, [FeCl4]1–/0, and [Fe(SCH3)4]1–/0 against vertical detachment energies (VDE) from valence photoelectron spectroscopy (PES), as a prelude to studies of metalloprotein analogs. The M06 and B3LYP hybrid functionals give VDE that agree with the PES VDE for the Fe complexes, but both underestimate it by 400 meV for the Cu complexes; other hybrid functionals give VDEs that are an increasing function of the amount of Hartree–Fock (HF) exchange and so cannot show good agreement for both Cu and Fe complexes. Range-separated (RS) functionals appear to give a better distribution of HF exchange since the negative HOMO energy is approximately equal to the VDEs but also give VDEs dependent on the amount of HF exchange, sometimes leading to ground states with incorrect electron configurations; the LRC-ωPBEh functional reduced to 10% HF exchange at short-range give somewhat better values for both, although still 150 meV too low for the Cu complexes and 50 meV too high for the Fe complexes. Overall, the results indicate that while HF exchange compensates for self-interaction error in DFT calculations of both Cu and Fe complexes, too much may lead to more sensitivity to nondynamical correlation in the spin-polarized Fe complexes.

  14. Energy band alignment in chalcogenide thin film solar cells from photoelectron spectroscopy.

    Science.gov (United States)

    Klein, Andreas

    2015-04-10

    Energy band alignment plays an important role in thin film solar cells. This article presents an overview of the energy band alignment in chalcogenide thin film solar cells with a particular focus on the commercially available material systems CdTe and Cu(In,Ga)Se2. Experimental results from two decades of photoelectron spectroscopy experiments are compared with density functional theory calculations taken from literature. It is found that the experimentally determined energy band alignment is in good agreement with theoretical predictions for many interfaces. These alignments, in particular the theoretically predicted alignments, can therefore be considered as the intrinsic or natural alignments for a given material combination. The good agreement between experiment and theory enables a detailed discussion of the interfacial composition of Cu(In,Ga)Se2/CdS interfaces in terms of the contribution of ordered vacancy compounds to the alignment of the energy bands. It is furthermore shown that the most important interfaces in chalcogenide thin film solar cells, those between Cu(In,Ga)Se2 and CdS and between CdS and CdTe are quite insensitive to the processing of the layers. There are plenty of examples where a significant deviation between experimentally-determined band alignment and theoretical predictions are evident. In such cases a variation of band alignment of sometimes more than 1 eV depending on interface preparation can be obtained. This variation can lead to a significant deterioration of device properties. It is suggested that these modifications are related to the presence of high defect concentrations in the materials forming the contact. The particular defect chemistry of chalcogenide semiconductors, which is related to the ionicity of the chemical bond in these materials and which can be beneficial for material and device properties, can therefore cause significant device limitations, as e.g. in the case of the CuInS2 thin film solar cells or for new

  15. Energetics and dissociation pathways of dimethyl disulfide and dimethyl diselenide using photoelectron photoion coincidence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Borkar, Sampada [Department of Chemistry, University of the Pacific, Stockton, CA 95211 (United States); Sztáray, Bálint, E-mail: bsztaray@pacific.edu [Department of Chemistry, University of the Pacific, Stockton, CA 95211 (United States); Bodi, Andras, E-mail: andras.boedi@psi.ch [Molecular Dynamics Group, Paul Scherrer Institut, Villigen 5232 (Switzerland)

    2014-10-15

    Internal energy selected dimethyl disulfide and dimethyl diselenide cations were prepared by vacuum ultraviolet threshold photoionization in Imaging Photoelectron Photoion Coincidence (iPEPICO) spectroscopy experiments. XH-, CH{sub 3}- and CH{sub n}X-loss reactions (n = 2–4, X = S, Se) were observed in both samples with varying branching ratios. SH loss from dimethyl disulfide, DMDS, and SeH loss from dimethyl diselenide were both found to be slow at threshold, and proceed through a tight transition state. By modeling the breakdown diagram and the ion time-of-flight distributions to extract unimolecular dissociation rates to account for kinetic shifts, we obtained a new, significantly revised 0 K SH-loss CH{sub 3}SCH{sub 2}{sup +} appearance energy. At slightly higher energies, CH{sub n}X{sup +} (n = 2–4) fragments are observed, still in the metastable energy range of the parent ion. Later, CH{sub 3}-loss outcompetes the lower energy channels and becomes dominant. At yet higher energies, the CH{sub 3}-loss fragment ion, probably CH{sub 3}X{sub 2}{sup +}, forms CHX{sup +} by H{sub 2}X abstraction. The newly obtained 0 K appearance energies are used in the ion cycle to discuss the heats of formation of CH{sub 3}SCH{sub 2}{sup +}, CH{sub 3}S{sub 2}{sup +}, CH{sub 2}S{sup +}, C{sub 2}H{sub 5}Se{sup +}, and CH{sub 3}Se{sub 2}{sup +}.

  16. Examining the Amine Functionalization in Dicarboxylates: Photoelectron Spectroscopy and Theoretical Studies of Aspartate and Glutamate

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Shihu; Hou, Gao-Lei; Kong, Xiangyu; Valiev, Marat; Wang, Xue B.

    2014-06-30

    Aspartate (Asp2-) and Glutamate (Glu2-), two doubly charged conjugate bases of the corresponding amino acids were investigated using low temperature negative ion photoelectron spectroscopy (NIPES) and ab-initio calculations. The effect of amine functionalization was studied by a direct comparison to the parent dicarboxylate species (-CO2–(CH2)n–CO2-, DCn2-) -- succinate (DC22-) and propionate (DC32-). Experimentally the addition of amine group for n = 2 case (DC22-, Asp2-) significantly improves the stability of the resultant Asp2- dianionic species, albeit that NIPES shows only a small increase in adiabatic electron detachment energy (ADE) (+0.05eV). In contrast, for n = 3 (DC32-, Glu2-), much larger ADE increase is observed (+0.15eV). Similar results are obtained through ab-initio calculations. The latter indicates that increased stability of Asp2- can be attributed to the lowering of the energy of singlet dianion state due to hydrogen bonding effects. The effect of the amino group on the doublet monoanion state is more complicated, and results in the weakening of the binding of the adjacent carboxylate group due to electronic structure resonance effects. This conclusion is confirmed by the analysis of NIPES results that show enhanced production of near zero kinetic energy electrons observed experimentally for amine-functionalized species.

  17. Birth of a resonant attosecond wavepacket

    Science.gov (United States)

    Argenti, L.; Gruson, V.; Barreau, L.; Jimenez-Galan, A.; Risoud, F.; Caillat, J.; Maquet, A.; Carre, B.; Lepetit, F.; Hergott, J.-F.; Ruchon, T.; Taieb, R.; Martin, F.; Salieres, P.

    2016-05-01

    Both amplitude and phase are needed to characterize the dynamics of a wavepacket. However, such characterization is difficult when both attosecond and femtosecond timescales are involved, as it is the case for broadband photoionization to a continuum encompassing autoionizing states. Here we demonstrate that Rainbow RABBIT, a new attosecond interferometry, allows the measurement of amplitude and phase of a photoelectron wavepacket created through a Fano resonance with unprecedented precision. In the experiment, a tunable attosecond pulse train is combined with the fundamental laser pulse to induce two-photon transitions in helium via an intermediate autoionizing state. From the energy and time-delay resolved signal, we fully reconstruct the resonant electron wavepacket as it builds up in the continuum. Measurements accurately match the predictions of a new time-resolved multi-photon resonant model, known to reproduce ab initio calculations. This agreement confirms the potential of Rainbow RABBIT to investigate photoemission delays in ultrafast processes governed by electron correlation, as well as to control structured electron wavepackets. now at Univ. Central Florida, Orlando, FL (USA).

  18. Interface Energy Alignment of Atomic-Layer-Deposited VOx on Pentacene: an in Situ Photoelectron Spectroscopy Investigation.

    Science.gov (United States)

    Zhao, Ran; Gao, Yuanhong; Guo, Zheng; Su, Yantao; Wang, Xinwei

    2017-01-18

    Ultrathin atomic-layer-deposited (ALD) vanadium oxide (VOx) interlayer has recently been demonstrated for remarkably reducing the contact resistance in organic electronic devices (Adv. Funct. Mater. 2016, 26, 4456). Herein, we present an in situ photoelectron spectroscopy investigation (including X-ray and ultraviolet photoelectron spectroscopies) of ALD VOx grown on pentacene to understand the role of the ALD VOx interlayer for the improved contact resistance. The in situ photoelectron spectroscopy characterizations allow us to monitor the ALD growth process of VOx and trace the evolutions of the work function, pentacene HOMO level, and VOx defect states during the growth. The initial VOx growth is found to be partially delayed on pentacene in the first ∼20 ALD cycles. The underneath pentacene layer is largely intact after ALD. The ALD VOx is found to contain a high density of defect states starting from 0.67 eV below the Fermi level, and the energy level of these defect states is in excellent alignment with the HOMO level of pentacene, which therefore allows these VOx defect states to provide an efficient hole-injection pathway at the contact interface.

  19. Implementation of Inverse Photoelectron Spectroscopy for Measuring the Empty Electronic States of Metal Oxide Surfaces

    Science.gov (United States)

    2014-11-05

    turbomolecular pump were also purchased from the DURIP funds. This equipment was installed in an existing photoelectron spectrometer in the Whitten group...auxiliary equipment, including a mass spectrometer for thermal desorption and a Kelvin probe. Figure 1: Photograph of the photoelectron spectrometer at...hydroxides and oxides and how this is affected by adsorption of hazardous gases. Ultimately, we are interested in correlating adsorbate-induced changes in

  20. Franck-Condon simulation of the anion photoelectron spectroscopy of CrO{sub 2} by coherent state method

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Guohua, E-mail: ghxu711@sohu.com; Yu, Feng

    2015-11-15

    Highlights: • A program to calculate multidimensional Franck-Condon integrals was developed. • The anion photoelectron spectroscopy of CrO{sub 2} was simulated and analyzed. • The calculated electron affinity of CrO{sub 2} is in agreement with the experiment. - Abstract: The equilibrium geometries and harmonic vibrational frequencies of CrO{sub 2}(X{sup 3}B{sub 1}) and CrO{sub 2}{sup -}(X{sup 4}B{sub 1}) were calculated using density functional theory and couple cluster method with various basis sets. A program was developed to calculate multidimensional Franck-Condon factors based on coherent state method. Its application to the photoelectron spectroscopy of the CrO{sub 2}(X{sup 3}B{sub 1})←CrO{sub 2}{sup -}(X{sup 4}B{sub 1}) photodetachment process was presented. The simulation at the CCSD(T)/aug-cc-pwCVTZ level of theory is in good agreement with the experimental spectroscopy, revealing that the hot bands contribute to the spectroscopy remarkably. All peaks of the experimental spectroscopy were assigned explicitly according to the theoretical modeling. Our calculations support original experimental assignments. In addition, the agreement between the calculated and experimental adiabatic electron affinities of CrO{sub 2}(X{sup 3}B{sub 1}) is excellent.

  1. Phase Determination Method to Directly Measure Intensity and Frequency of Temporal Profiles of Attosecond EUV Pulses

    Institute of Scientific and Technical Information of China (English)

    GE Yu-Cheng

    2005-01-01

    @@ A new method of phase determination is presented to directly measure the intensity and frequency temporalprofiles of attosecond EUV pulses. The profiles can be reconstructed from the photoelectron energy spectra measured with two different laser intensities at 0° and 180° with respect to the linear laser polarization using a cross correlation between the femtosecond laser and the attosecond EUV. The method has a temporal measurement range from a quarter to about half of a laser oscillation period. The time resolution depends on the jitter and control precision of laser and EUV pulses. This method improves the time resolution in measuring attosecond EUV pulses.

  2. Direct work function measurement by gas phase photoelectron spectroscopy and its application on PbS nanoparticles.

    Science.gov (United States)

    Axnanda, Stephanus; Scheele, Marcus; Crumlin, Ethan; Mao, Baohua; Chang, Rui; Rani, Sana; Faiz, Mohamed; Wang, Suidong; Alivisatos, A Paul; Liu, Zhi

    2013-01-01

    Work function is a fundamental property of a material's surface. It is playing an ever more important role in engineering new energy materials and efficient energy devices, especially in the field of photovoltaic devices, catalysis, semiconductor heterojunctions, nanotechnology, and electrochemistry. Using ambient pressure X-ray photoelectron spectroscopy (APXPS), we have measured the binding energies of core level photoelectrons of Ar gas in the vicinity of several reference materials with known work functions (Au(111), Pt(111), graphite) and PbS nanoparticles. We demonstrate an unambiguously negative correlation between the work functions of reference samples and the binding energies of Ar 2p core level photoelectrons detected from the Ar gas near the sample surface region. Using this experimentally determined linear relationship between the surface work function and Ar gas core level photoelectron binding energy, we can measure the surface work function of different materials under different gas environments. To demonstrate the potential applications of this ambient pressure XPS technique in nanotechnology and solar energy research, we investigate the work functions of PbS nanoparticles with various capping ligands: methoxide, mercaptopropionic acid, and ethanedithiol. Significant Fermi level position changes are observed for PbS nanoparticles when the nanoparticle size and capping ligands are varied. The corresponding changes in the valence band maximum illustrate that an efficient quantum dot solar cell design has to take into account the electrochemical effect of the capping ligand as well.

  3. Effects of electronic coherence in ultrafast spectroscopy

    Science.gov (United States)

    Bennett, Kochise

    Electronic dynamics takes place at the attosecond timescale. Recent technological advancements permit the creation of light pulses with durations in the attosecond regime, opening up the possibility of monitoring this ultrafast dynamics in real time. In particular, it becomes possible to observe the time-dependent interference between material electronic states, thus tracking the electronic energies temporally. This information, originating in the coherence terms in the electronic density matrix, can provide spectral information in the time-domain. Such an approach is particularly useful when the desired information is transient. In this thesis, we examine how electronic coherences contribute to photoelectron and a variety of x-ray Raman signals. We then utilize photoelectron spectroscopy and linear off-resonant Raman (TRUECARS) to track the dynamics of a model system by way of example.

  4. Study on the ultrafast dynamics of o-xylene cation by combined fs-photoelectron imaging-photofragmentation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yuzhu, E-mail: yuzhu.liu@psi.ch; Radi, Peter; Gerber, Thomas; Knopp, Gregor, E-mail: gregor.knopp@psi.ch

    2014-10-17

    Highlights: • Photoelectron imaging and photofragment spectroscopy are combined. • Photoelectron imaging has been measured to characterize the prepared cation states. • Ultrafast signal decay with time constant of 734 (±61) fs has been observed. - Abstract: Ultrafast dynamics of o-xylene cation has been studied by time resolved fs-photofragmentation (PF) spectroscopy in combination with photoelectron imaging (PEI). In the experiment, multiphoton ionization is used to prepare the o-xylene cation characterized by PEI. The ultrafast dynamics of o-xylene ions are measured by monitoring the time dependent parent-ion depletion and the fragment-ion formation, simultaneously. An ultrafast relaxation time of the parent ion of 734 (±61) fs has been observed. The PEI-PF measurements support the interpretation of this relaxation channel to a combination of internal conversion between the two ionic states (D{sub 0} and D{sub 1}) and intramolecular vibrational-energy redistribution process within the D{sub 0} state.

  5. The Ultraviolet Photoelectron Spectroscopy of Group IV 2-15 Atom Cluster Anions

    Science.gov (United States)

    Craycraft, Mary Jo.

    The ability to map valence electronic structure is the result of a recent advance in photoelectron spectroscopy; its union with cluster molecular beam technology. The task of interpreting the spectra is hampered by a serious lack of understanding of cluster electronic structure in general. Recently progress has been made in finding models for single s valence electron systems. Alkali and noble metal clusters can be treated as free electron systems and simple interatomic potentials can be used with rare gas clusters. Neither a smeared jellium background nor a simple interatomic potential is adequate to describe covalent bonding, however. The isoelectronic Group IV members have a valence configuration of ns^2 np^2. All readily form clusters, and the elements differ in both their atomic and bulk properties; thus the series provides an ideal system for studying electronic structure. The mass selected cluster ion beam is crossed with a beam (6.42 or 7.9eV) and the resulting photodetached electrons collected with the aid of judiciously arranged magnetic fields. The spectra are found to be unique for each size cluster. Some spectra show a significant gap between the two lowest binding energy features, indicating that the neutral cluster is a closed shell species. The clusters with such gaps are minima in a plot of EA as a function of cluster size. The UPS also vary with the cluster composition. Carbon is unique; an even -odd alternation in electron affinities switches from odd minima for clusters containing less than ten atoms to odd maxima for larger clusters. This corresponds with an alternation in singlet and triplet ground states and a switch from chain to ring structures previously predicted by theory (K. S. Pitzer, E. Clementi, J. Amer. Chem. Soc. 81 4477 (1958) and R. Hoffmann, Tetrahedron 22 521 (1965)). The spectra of the remaining group IV members are remarkably similar to each other for clusters of up to ten atoms, as is the trend in the electron affinities as

  6. Femtosecond photoelectron spectroscopy: a new tool for the study of anion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Greenblatt, Benjamin J. [Univ. of California, Berkeley, CA (United States)

    1999-02-01

    A new experimental technique for the time-resolved study of anion reactions is presented. Using femtosecond laser pulses, which provide extremely fast (~100 fs) time resolution, in conjunction with photoelectron spectroscopy, which reveals differences between anion and neutral potential energy surfaces, a complex anion reaction can be followed from its inception through the formation of asymptotic products. Experimental data can be modeled quantitatively using established theoretical approaches, allowing for the refinement of potential energy surfaces as well as dynamical models. After a brief overview, a detailed account of the construction of the experimental apparatus is presented. Documentation of the data acquisition program is contained in the Appendix. The first experimental demonstration of the technique is then presented for I2- photodissociation, modeled using a simulation program which is also detailed in the Appendix. The investigation of I2- photodissociation in several size-selected I2-(Ar)n (n = 6-20) and I2-(CO2)n (n = 4-16) clusters forms the heart of the dissertation. In a series of chapters, the numerous effects of solvation on this fundamental bond-breaking reaction are explored, the most notable of which is the recombination of I2- on the ground $\\tilde{X}$(2Σu+) state in sufficiently large clusters. Recombination and trapping of I2- on the excited $\\tilde{A}$(2π3/2,g) state is also observed in both types of clusters. The studies have revealed electronic state transitions, the first step in recombination, on a ~500 fs to ~10 ps timescale. Accompanying the changes in electronic state is solvent reorganization, which occurs on a similar timescale. Over longer periods (~1 ps to >200 ps), energy is transferred from vibrationally

  7. Femtosecond photoelectron spectroscopy: a new tool for the study of anion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Greenblatt, B.J.

    1999-02-01

    A new experimental technique for the time-resolved study of anion reactions is presented. Using femtosecond laser pulses, which provide extremely fast ({approx} 100 fs) time resolution, in conjunction with photoelectron spectroscopy, which reveals differences between anion and neutral potential energy surfaces, a complex anion reaction can be followed from its inception through the formation of asymptotic products. Experimental data can be modeled quantitatively using established theoretical approaches, allowing for the refinement of potential energy surfaces as well as dynamical models. After a brief overview, a detailed account of the construction of the experimental apparatus is presented. Documentation of the data acquisition program is contained in the Appendix. The first experimental demonstration of the technique is then presented for I{sub 2}{sup -} photodissociation, modeled using a simulation program which is also detailed in the Appendix. The investigation of I{sub 2}{sup -} photodissociation in several size-selected I{sub 2}{sup -}(Ar){sub n} (n = 6-20) and I{sub 2}{sup -}(CO{sub 2}){sub n} (n = 4-16) clusters forms the heart of the dissertation. In a series of chapters, the numerous effects of solvation on this fundamental bond-breaking reaction are explored, the most notable of which is the recombination of I{sub 2}{sup -} on the ground {tilde X}({sup 2}{Sigma}{sub u}{sup +}) state in sufficiently large clusters. Recombination and trapping of I{sub 2}{sup -} on the excited {tilde A}({sup 2}{Pi}{sub 3/2,g}) state is also observed in both types of clusters. The studies have revealed electronic state transitions, the first step in recombination, on a {approx}500 fs to {approx}10 ps timescale. Accompanying the changes in electronic state is solvent reorganization, which occurs on a similar timescale. Over longer periods ({approx}1 ps to >200 ps), energy is transferred from vibrationally excite d I{sub 2}{sup -} to modes of the solvent, which in turn leads

  8. Radiation effects and metalloproteins studied by x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wurzbach, J.A.

    1975-07-01

    X-ray photoelectron spectroscopy (XPS) is used to study the bonding structure at the iron site of cytochrome c and the bonding of rare earth ions to the phosphate oxygens of ATP. Radiation effects are studied on several amino acid and simple peptide model systems. The emission spectrum of the x-ray source is calculated from literature references. The distributions of photon energy as a function of photon frequency and as a function of take-off angle are obtained. From these distributions, the radiation dose absorbed by an organic sample is found to be 10/sup 6/ rads/sec. The C 1s and N 1s spectra of amino acids and peptides are studied to characterize an internal reference standard for protein XPS spectra. Samples of native cytochrome c prepared from solutions of pH 1.5, 3, 7, and 11 are studied. Control samples include porphyrin cytochrome c (PCC), the metal free analogue of the native protein, and microperoxidase (MP), a mixture of heme peptides derived from the peptic digestion of cytochrome c. These samples show two S 2p peaks. The first peak has a binding energy (BE) of 163 eV, which corresponds to the S containing amino acids; the second peak is shifted to 167 eV. This large shift may be the result of Fe-S binding, or oxidation, or both. Low spin ferricytochrome c and ferri-MP were found to have Fe 3p BE's that are unusually low (51 eV) compared to other ferric compounds (54 to 58 eV) and even Fe metal (53 eV). X-ray crystal structures of these compounds show that low spin heme Fe lies in the porphyrin plane; while, high spin heme Fe is displaced above the plane. The N 1s and P 2p spectra of ATP show no change except slight broadening when Nd/sup 3 +/ is substituted for Na/sup +/. Thus, there is no inconsistency with proposals that rare earth ions might be useful as substitutes for alkali metal ions and alkaline earth ions in proteins.

  9. Band structures of 4f and 5f materials studied by angle-resolved photoelectron spectroscopy

    Science.gov (United States)

    Fujimori, Shin-ichi

    2016-04-01

    Recent remarkable progress in angle-resolved photoelectron spectroscopy (ARPES) has enabled the direct observation of the band structures of 4f and 5f materials. In particular, ARPES with various light sources such as lasers (hν ∼ 7~\\text{eV} ) or high-energy synchrotron radiations (hν ≳ 400~\\text{eV} ) has shed light on the bulk band structures of strongly correlated materials with energy scales of a few millielectronvolts to several electronvolts. The purpose of this paper is to summarize the behaviors of 4f and 5f band structures of various rare-earth and actinide materials observed by modern ARPES techniques, and understand how they can be described using various theoretical frameworks. For 4f-electron materials, ARPES studies of \\text{Ce}M\\text{I}{{\\text{n}}5} (M=\\text{Rh} , \\text{Ir} , and \\text{Co} ) and \\text{YbR}{{\\text{h}}2}\\text{S}{{\\text{i}}2} with various incident photon energies are summarized. We demonstrate that their 4f electronic structures are essentially described within the framework of the periodic Anderson model, and that the band-structure calculation based on the local density approximation cannot explain their low-energy electronic structures. Meanwhile, electronic structures of 5f materials exhibit wide varieties ranging from itinerant to localized states. For itinerant \\text{U}~5f compounds such as \\text{UFeG}{{\\text{a}}5} , their electronic structures can be well-described by the band-structure calculation assuming that all \\text{U}~5f electrons are itinerant. In contrast, the band structures of localized \\text{U}~5f compounds such as \\text{UP}{{\\text{d}}3} and \\text{U}{{\\text{O}}2} are essentially explained by the localized model that treats \\text{U}~5f electrons as localized core states. In regards to heavy fermion \\text{U} -based compounds such as the hidden-order compound \\text{UR}{{\\text{u}}2}\\text{S}{{\\text{i}}2} , their electronic structures exhibit complex behaviors. Their overall band structures

  10. Nanocrystalline tin oxide: Possible origin of its weak ferromagnetism deduced from nuclear magnetic resonance and X-ray photoelectron spectroscopies

    Science.gov (United States)

    Zhang, Feng; Lian, Yadong; Gu, Min; Yu, Ji; Tang, Tong B.; Sun, Jian; Zhang, Weiyi

    2016-09-01

    Nanocrystalline tin oxide was fabricated, with molar ratio O/Sn determined as 1.40, 1.55, 1.79, 1.92 and 1.96 from X-ray photoelectron spectroscopy. They displayed weak ferromagnetism, the sample with O/Sn = 1.55 showing the maximum saturation magnetization reaching almost 8 ×10-3 emu /g at room temperature. 119Sn nuclear magnetic resonance allowed the deduction, based on four resolved resonance peaks, that their Sn ions had four possible coordination numbers, namely 3, 4, 5 and 6. The relative fraction of 4-coordinated cations was the one found to bear positive linear correlation with saturation magnetization of the sample. It is surmised that magnetism in tin oxide results mainly from 4-coordination Sn ions, of valance about +3, as estimated from the binding energies of their 3d photoelectron emission levels.

  11. Metal-polymer interfaces studied with adsorption microcalorimetry and photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bebensee, Fabian

    2010-06-21

    The interface formation between calcium and two different semiconducting, ?-conjugated polymers, namely poly(3-hexylthiophene) (P3HT) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovilylene)phenylene] (CN-MEH-PPV), was investigated using adsorption microcalorimetry, low energy ion scattering spectroscopy (LEIS), atomic beam scattering and X-ray photoelectron spectroscopy. In addition to the interface formation on pristine, i.e., untreated polymer surfaces, the influence of electron irradiation prior to calcium deposition and the effect of dosing calcium at a low substrate temperature was studied. The reactive site for the interaction of calcium atoms impinging on a pristine P3HT surface appears to be the sulfur in the thiophene ring, as is concluded from a combination of XPS, adsorption calorimetry and theory results. The interaction, in fact, is strong enough that the sulfur atoms abstracted from the thiophene ring under formation of calcium sulfide with an overall reaction energy of this process of 405 kJ per mol. Quantitative evaluation of XPS data reveal that the depth up to which Ca atoms react with sulfur in the polymer is 3 nm, irrespective of increasing the amount of Ca dosed onto the substrate. A closed layer of Ca is only formed at a Ca coverage exceeding 11 ML, as suggested by LEIS. Irradiation of P3HT with electrons with a kinetic energy of 100 eV results in dehydrogenation of the hexyl side chains and formation of new C=C double bonds. This in turn results in a higher initial sticking probability of 0.63 for Ca, while no other significant changes could be observed: XPS indicates that the thiophene rings remain intact and the measured heat of adsorption is the same as observed for the deposition of Ca on pristine P3HT. Dosing Ca onto P3HT held at low temperature (130 K) is found to result in a very low saturation thickness of the reacted layer of approximately 0.3 nm. Upon warming the sample up to room temperature, the thickness of the reacted layer

  12. Ultrafast dynamics of o-fluorophenol studied with femtosecond time-resolved photoelectron and photoion spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The ultrafast dynamics of o-fluorophenol via the excited states has been studied by femtosecond time-resolved photoelectron imaging. The photoion and photoelectron spectra taken with a time delay between 267 nm pump laser and 800 nm probe laser provide a longer-lived S1 electronic state of about ns timescale. In comparison,the spectra obtained by exciting the S2 state with femtosecond laser pulses at 400 nm and ionizing with pulses at 800 nm suggest that the S2 state has an ultrashort lifetime about 102 fs and reflects the internal conversion dynamics of the S2 state to the S1 state.

  13. Oxidation of nanostructured Ti films produced by low energy cluster beam deposition: An X-ray Photoelectron Spectroscopy characterization

    Energy Technology Data Exchange (ETDEWEB)

    Simone, Monica de, E-mail: desimone@tasc.infm.it [CNR-IOM Laboratorio TASC, Area Science Park Basovizza, 34149 Trieste (Italy); Snidero, Elena [CNR-IOM Laboratorio TASC, Area Science Park Basovizza, 34149 Trieste (Italy); Coreno, Marcello [CNR-IMIP, c/o Laboratorio TASC Area Science Park Basovizza, 34149 Trieste (Italy); Sincrotrone Trieste ScpA, Area Science Park Basovizza, 34149 Trieste (Italy); Bongiorno, Gero [Fondazione Filarete, v.le Ortles 22/4, 20139 Milano (Italy); Giorgetti, Luca [Istituto Europeo di Oncologia, Dip. di Oncologia Sperimentale, Via Adamello 16, 20139, Milano (Italy); Amati, Matteo [Sincrotrone Trieste ScpA, Area Science Park Basovizza, 34149 Trieste (Italy); Cepek, Cinzia [CNR-IOM Laboratorio TASC, Area Science Park Basovizza, 34149 Trieste (Italy)

    2012-05-01

    We used in-situ X-ray Photoelectron Spectroscopy (XPS) to study the oxidation process of a cluster-assembled metallic titanium film exposed to molecular oxygen at room temperature. The nanostructured film has been grown on a Si(111) substrate, in ultra high vacuum conditions, by coupling a supersonic cluster beam deposition system with an XPS experimental chamber. Our results show that upon in-situ oxygen exposure Ti{sup 3+} is the first oxidation state observed, followed by Ti{sup 4+}, whereas Ti{sup 2+} is practically absent during the whole process. Our results compare well with the existing literature on Ti films produced using other techniques.

  14. Highly polarized emission in spin resolved photoelectron spectroscopy of alpha-Fe(001)/GaAs(001)

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, James; Yu, Sung Woo; Morton, Simon; Waddill, George; Thompson, Jamie; Neal, James; Spangenberg, Matthais; Shen, T.H.

    2009-05-19

    Highly spin-polarized sources of electrons, Integrated into device design, remain of great interest to the spintronic and magneto-electronic device community Here, the growth of Fe upon GaAs(001) has been studied with photoelectron spectroscopy (PES), including Spin Resolved PES. Despite evidence of atomic level disorder such as intermixing, an over-layer with the spectroscopic signature of alpha-Fe(001), with a bcc real space ordering, Is obtained The results will be discussed in light of the possibility of using such films as a spin-polarized source in device applications.

  15. Band alignment at the interface of PbTe/SnTe heterojunction determined by X-ray photoelectron spectroscopy

    Science.gov (United States)

    Shu, Tianyu; Ye, Zhenyu; Lu, Pengqi; Chen, Lu; Xu, Gangyi; Zhou, Jie; Wu, Huizhen

    2016-11-01

    We report the determination of band alignment of PbTe/SnTe (111) heterojunction interfaces using X-ray photoelectron spectroscopy (XPS). Multiple core levels of Pb and Sn were utilized to determine the valence band offset (VBO) of the heterojunction. The XPS result shows a type-III band alignment with the VBO of 1.37+/- 0.18 \\text{eV} and the conduction band offset (CBO) of 1.23+/- 0.18 \\text{eV} . The experimental determination of the band alignment of the PbTe/SnTe heterojunction shall benefit the improvement of PbTe/SnTe-related optoelectronic and electronic devices.

  16. Application of maximum-entropy spectral estimation to deconvolution of XPS data. [X-ray Photoelectron Spectroscopy

    Science.gov (United States)

    Vasquez, R. P.; Klein, J. D.; Barton, J. J.; Grunthaner, F. J.

    1981-01-01

    A comparison is made between maximum-entropy spectral estimation and traditional methods of deconvolution used in electron spectroscopy. The maximum-entropy method is found to have higher resolution-enhancement capabilities and, if the broadening function is known, can be used with no adjustable parameters with a high degree of reliability. The method and its use in practice are briefly described, and a criterion is given for choosing the optimal order for the prediction filter based on the prediction-error power sequence. The method is demonstrated on a test case and applied to X-ray photoelectron spectra.

  17. Measurement of the CdSe/ZnTe valence band offset by x-ray photoelectron spectroscopy

    OpenAIRE

    E. T. Yu; Phillips, M. C.; McCaldin, J. O.; McGill, T. C.

    1991-01-01

    We have used x-ray photoelectron spectroscopy (XPS) to measure the valence band offset in situ for CdSe/ZnTe (100) heterojunctions grown by molecular-beam epitaxy. XPS measurements were performed for films of CdSe (100) and ZnTe (100), and for heterojunctions consisting of either ~25 Å of CdSe grown on ZnTe or ~25 Å of ZnTe grown on CdSe. Observations of reflection high energy electron diffraction patterns indicated that CdSe films deposited on ZnTe were grown in cubic zinc blende form, rathe...

  18. A combined photoelectron spectroscopy and relativistic ab initio studies of the electronic structures of UFO and UFO-

    Science.gov (United States)

    Roy, Soumendra K.; Jian, Tian; Lopez, Gary V.; Li, Wei-Li; Su, Jing; Bross, David H.; Peterson, Kirk A.; Wang, Lai-Sheng; Li, Jun

    2016-02-01

    The observation of the gaseous UFO- anion is reported, which is investigated using photoelectron spectroscopy and relativisitic ab initio calculations. Two strong photoelectron bands are observed at low binding energies due to electron detachment from the U-7sσ orbital. Numerous weak detachment bands are also observed due to the strongly correlated U-5f electrons. The electron affinity of UFO is measured to be 1.27(3) eV. High-level relativistic quantum chemical calculations have been carried out on the ground state and many low-lying excited states of UFO to help interpret the photoelectron spectra and understand the electronic structure of UFO. The ground state of UFO- is linear with an O-U-F structure and a 3H4 spectral term derived from a U 7sσ25fφ15fδ1 electron configuration, whereas the ground state of neutral UFO has a 4H7/2 spectral term with a U 7sσ15fφ15fδ1 electron configuration. Strong electron correlation effects are found in both the anionic and neutral electronic configurations. In the UFO neutral, a high density of electronic states with strong configuration mixing is observed in most of the scalar relativistic and spin-orbit coupled states. The strong electron correlation, state mixing, and spin-orbit coupling of the electronic states make the excited states of UFO very challenging for accurate quantum chemical calculations.

  19. Pump laser-induced space-charge effects in HHG-driven time- and angle-resolved photoelectron spectroscopy

    Science.gov (United States)

    Oloff, L.-P.; Hanff, K.; Stange, A.; Rohde, G.; Diekmann, F.; Bauer, M.; Rossnagel, K.

    2016-06-01

    With the advent of ultrashort-pulsed extreme ultraviolet sources, such as free-electron lasers or high-harmonic-generation (HHG) sources, a new research field for photoelectron spectroscopy has opened up in terms of femtosecond time-resolved pump-probe experiments. The impact of the high peak brilliance of these novel sources on photoemission spectra, so-called vacuum space-charge effects caused by the Coulomb interaction among the photoemitted probe electrons, has been studied extensively. However, possible distortions of the energy and momentum distributions of the probe photoelectrons caused by the low photon energy pump pulse due to the nonlinear emission of electrons have not been studied in detail yet. Here, we systematically investigate these pump laser-induced space-charge effects in a HHG-based experiment for the test case of highly oriented pyrolytic graphite. Specifically, we determine how the key parameters of the pump pulse—the excitation density, wavelength, spot size, and emitted electron energy distribution—affect the measured time-dependent energy and momentum distributions of the probe photoelectrons. The results are well reproduced by a simple mean-field model, which could open a path for the correction of pump laser-induced space-charge effects and thus toward probing ultrafast electron dynamics in strongly excited materials.

  20. Coincidence and covariance data acquisition in photoelectron and -ion spectroscopy. I. Formal theory

    Science.gov (United States)

    Mikosch, Jochen; Patchkovskii, Serguei

    2013-10-01

    We derive a formal theory of noisy Poisson processes with multiple outcomes. We obtain simple, compact expressions for the probability distribution function of arbitrarily complex composite events and its moments. We illustrate the utility of the theory by analyzing properties of coincidence and covariance photoelectron-photoion detection involving single-ionization events. The results and techniques introduced in this work are directly applicable to more general coincidence and covariance experiments, including multiple ionization and multiple-ion fragmentation pathways.

  1. Photoelectron spectroscopy of liquid water, some alcohols, and pure nonane in free micro jets

    Science.gov (United States)

    Faubel, Manfred; Steiner, Björn; Toennies, J. Peter

    1997-06-01

    The recently developed technique of accessing volatile liquids in a high vacuum environment by using a very thin liquid jet is implemented to carry out the first measurements of photoelectron spectra of pure liquid water, methanol, ethanol, 1-propanol, 1-butanol, and benzyl alcohol as well as of liquid n-nonane. The apparatus, which consists of a commercial hemispherical (10 cm mean radius) electron analyzer and a hollow cathode discharge He I light source is described in detail and the problems of the sampling of the photoelectrons in such an environment are discussed. For water and most of the alcohols up to six different electronic bands could be resolved. The spectra of 1-butanol and n-nonane show two weakly discernable peaks from which the threshold ionization potential could be determined. A deconvolution of the photoelectron spectra is used to extract ionization potentials of individual molecular bands of molecules near the surface of the liquid and shifts of the order of 1 eV compared to the gas phase are observed. A molecular orientation for water molecules at the surface of liquid water is inferred from a comparison of the relative band strengths with the gas phase. Similar effects are also observed for some of the alcohols. The results are discussed in terms of a simple "Born-solvation" model.

  2. A facility for the analysis of the electronic structures of solids and their surfaces by synchrotron radiation photoelectron spectroscopy.

    Science.gov (United States)

    Hoesch, M; Kim, T K; Dudin, P; Wang, H; Scott, S; Harris, P; Patel, S; Matthews, M; Hawkins, D; Alcock, S G; Richter, T; Mudd, J J; Basham, M; Pratt, L; Leicester, P; Longhi, E C; Tamai, A; Baumberger, F

    2017-01-01

    A synchrotron radiation beamline in the photon energy range of 18-240 eV and an electron spectroscopy end station have been constructed at the 3 GeV Diamond Light Source storage ring. The instrument features a variable polarisation undulator, a high resolution monochromator, a re-focussing system to form a beam spot of 50 × 50 μm(2), and an end station for angle-resolved photoelectron spectroscopy (ARPES) including a 6-degrees-of-freedom cryogenic sample manipulator. The beamline design and its performance allow for a highly productive and precise use of the ARPES technique at an energy resolution of 10-15 meV for fast k-space mapping studies with a photon flux up to 2 ⋅ 10(13) ph/s and well below 3 meV for high resolution spectra.

  3. A facility for the analysis of the electronic structures of solids and their surfaces by synchrotron radiation photoelectron spectroscopy

    Science.gov (United States)

    Hoesch, M.; Kim, T. K.; Dudin, P.; Wang, H.; Scott, S.; Harris, P.; Patel, S.; Matthews, M.; Hawkins, D.; Alcock, S. G.; Richter, T.; Mudd, J. J.; Basham, M.; Pratt, L.; Leicester, P.; Longhi, E. C.; Tamai, A.; Baumberger, F.

    2017-01-01

    A synchrotron radiation beamline in the photon energy range of 18-240 eV and an electron spectroscopy end station have been constructed at the 3 GeV Diamond Light Source storage ring. The instrument features a variable polarisation undulator, a high resolution monochromator, a re-focussing system to form a beam spot of 50 × 50 μm2, and an end station for angle-resolved photoelectron spectroscopy (ARPES) including a 6-degrees-of-freedom cryogenic sample manipulator. The beamline design and its performance allow for a highly productive and precise use of the ARPES technique at an energy resolution of 10-15 meV for fast k-space mapping studies with a photon flux up to 2 ṡ 1013 ph/s and well below 3 meV for high resolution spectra.

  4. X-ray photoelectron spectroscopy study of irradiation-induced amorphizaton of Gd2Ti2O7

    Science.gov (United States)

    Chen, J.; Lian, J.; Wang, L. M.; Ewing, R. C.; Boatner, L. A.

    2001-09-01

    The radiation-induced evolution of the microstructure of Gd2Ti2O7, an important pyrochlore phase in radioactive waste disposal ceramics and a potential solid electrolyte and oxygen gas sensor, has been characterized using transmission electron microscopy and x-ray photoelectron spectroscopy. Following the irradiation of a Gd2Ti2O7 single crystal with 1.5 MeV Xe+ ions at a fluence of 1.7×1014Xe+/cm2, cross-sectional transmission electron microscopy revealed a 300-nm-thick amorphous layer at the specimen surface. X-ray photoelectron spectroscopy analysis of the Ti 2p and O 1s electron binding energy shifts of Gd2Ti2O7 before and after amorphization showed that the main results of ion-irradiation-induced disorder are a decrease in the coordination number of titanium and a transformation of the Gd-O bond. These features resemble those occurring in titanate glass formation, and they have implications for the chemical stability and electronic properties of pyrochlores subjected to displacive radiation damage.

  5. 50 years anniversary of the discovery of the core level chemical shifts. The early years of photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mårtensson, Nils [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden); Sokolowski, Evelyn [Tvär-Ramsdal 1, 611 99 Tystberga (Sweden); Svensson, Svante, E-mail: Svante.Svensson@fysik.uu.se [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden)

    2014-03-01

    Highlights: • 50 years since the discovery of t the core level chemical shift. • The pioneering years of ESCA. • A critical review of the first core electron chemical shift results. - Abstract: The pioneering years of photoelectron spectroscopy in Uppsala are discussed, especially the work leading to the discovery of the core level chemical shifts. At a very early stage of the project, the pioneering group observed what they described as evidence for chemical shifts in the core level binding energies. However, it can now be seen that the initial observations to a large extent was due to charging of the samples. It is interesting to note that the decisive experiment was realized, not as a result of a systematic study, but was obtained with a large element of serendipity. Only when a chemical binding energy shift was observed between two S2p electron lines in the same molecule, the results were accepted internationally, and the fascinating expansion of modern core level photoelectron spectroscopy could start.

  6. Irradiation-induced degradation of PTB7 investigated by valence band and S 2p photoelectron spectroscopy

    Science.gov (United States)

    Darlatt, Erik; Muhsin, Burhan; Roesch, Roland; Lupulescu, Cosmin; Roth, Friedrich; Kolbe, Michael; Gottwald, Alexander; Hoppe, Harald; Richter, Mathias

    2016-08-01

    Monochromatic radiation with known absolute radiant power from an undulator at the electron storage ring Metrology Light Source (MLS) was used to irradiate PTB7 (a thieno[3, 4-b]thiophene-alt-benzodithiophene polymer) thin films at wavelengths (photon energies) of 185 nm (6.70 eV), 220 nm (5.64 eV), 300 nm (4.13 eV), 320 nm (3.88 eV), 356 nm (3.48 eV) and 675 nm (1.84 eV) under ultra-high vacuum conditions for the investigation of radiation-induced degradation effects. The characterization of the thin films is focused at ultraviolet photoelectron spectroscopy (UPS) of valence bands and is complemented by S 2p x-ray photoelectron spectroscopy (S 2p XPS) before and after the irradiation procedure. The radiant exposure was determined for each irradiation by means of photodiodes traceably calibrated to the international system of units SI. The valence band spectra show the strongest changes for the shortest wavelengths and no degradation effect at 356 nm and 675 nm even with the highest radiant exposure applied. In the spectral range where the Sun appears bright on the Earth’s surface, no degradation effects are observed.

  7. A simple electron time-of-flight spectrometer for ultrafast vacuum ultraviolet photoelectron spectroscopy of liquid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Arrell, C. A., E-mail: christopher.arrell@epfl.ch; Ojeda, J.; Mourik, F. van; Chergui, M. [Laboratory of Ultrafast Spectroscopy, ISIC, Station 6, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Sabbar, M.; Gallmann, L.; Keller, U. [Physics Department, ETH Zurich, 8093 Zurich (Switzerland); Okell, W. A.; Witting, T.; Siegel, T.; Diveki, Z.; Hutchinson, S.; Tisch, J. W.G.; Marangos, J. P. [Department of Physics, The Blackett Laboratory, Imperial College, London SW7 2AZ (United Kingdom); Chapman, R. T.; Cacho, C.; Rodrigues, N.; Turcu, I. C.E.; Springate, E. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxon OX11 0QX (United Kingdom)

    2014-10-01

    We present a simple electron time of flight spectrometer for time resolved photoelectron spectroscopy of liquid samples using a vacuum ultraviolet (VUV) source produced by high-harmonic generation. The field free spectrometer coupled with the time-preserving monochromator for the VUV at the Artemis facility of the Rutherford Appleton Laboratory achieves an energy resolution of 0.65 eV at 40 eV with a sub 100 fs temporal resolution. A key feature of the design is a differentially pumped drift tube allowing a microliquid jet to be aligned and started at ambient atmosphere while preserving a pressure of 10⁻¹ mbar at the micro channel plate detector. The pumping requirements for photoelectron (PE) spectroscopy in vacuum are presented, while the instrument performance is demonstrated with PE spectra of salt solutions in water. The capability of the instrument for time resolved measurements is demonstrated by observing the ultrafast (50 fs) vibrational excitation of water leading to temporary proton transfer.

  8. Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Nordlund, Dennis; Odelius, Michael; Bluhm, Hendrik; Ogasawara, Hirohito; Pettersson, Lars G.M.; Nilsson, Anders

    2008-04-29

    We present valence photoelectron emission spectra of liquid water in comparison with gas-phase water, ice close to the melting point, low temperature amorphous and crystalline ice. All aggregation states have major electronic structure changes relative to the free molecule, with rehybridization and development of bonding and anti-bonding states accompanying the hydrogen bond formation. Sensitivity to the local structural order, most prominent in the shape and splitting of the occupied 3a{sub 1} orbital, is understood from the electronic structure averaging over various geometrical structures, and reflects the local nature of the orbital interaction.

  9. Investigation of low-Z Coster-Kronig transitions by means of Auger and photoelectron spectroscopy

    Science.gov (United States)

    Yin, L. I.; Tsang, T.; Adler, I.

    1972-01-01

    Experimental intensity ratios of Auger transitions for Co, Ni, Cu, and Zn as well as the relative L sub 2 and L sub 3 level widths of Cu and Zn, derived from their photoelectron spectra, are presented. Evidence is presented that a great deal of vacancy reorganization took place following photoionization and prior to Auger emission. These reorganizations are assumed to be due to Coster-Kronig transitions f sub 23. These results are compared with theoretical calculations and agree with predicted discontinuity at Z = 30 where f sub 23 transitions become energetically impossible.

  10. Short-range order in amorphous SiO{sub x} by x ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, Yu. N.; Gritsenko, V. A. [Institute of Semiconductor Physics, Novosibirsk 630090 (Russian Federation)

    2011-07-01

    The Si 2p x ray photoelectron spectra of SiO{sub x} with a different composition of 0 {<=} x {<=} 2 have been studied experimentally and theoretically. The SiO{sub x} films were prepared by low-pressure chemical vapor deposition from SiH{sub 4} and N{sub 2}O source at 750 deg. C. Neither random bonding nor random mixture models can adequately describe the structure of these compounds. The interpretation of the experimental results is discussed according to a large scale potential fluctuation due to the spatial variation of chemical composition in SiO{sub x}.

  11. Manifestation of attosecond XUV fields temporal structures in attosecond streaking spectrogram

    Institute of Scientific and Technical Information of China (English)

    Guanglong Chen; Yunjiu Cao; Dong Eon Kim

    2011-01-01

    @@ The features of an attosecond extreme ultraviolet (XUV) field are encoded in the attosecond XUV spectrogram.We investigate the effect of the temporal structures of attosecond XUV fields on the attosecond streaking spectrogram.Factors such as the number of attosecond XUV pulses and the temporal chirp of attosecond XUV pulses are considered.Results indicate that unlike the attosecond streaking spectrogram for an attosecond XUV field with two pulses of a half-cycle separation of streaking field, the spectrogram for the attosecond XUV field with three pulses demonstrates fine spectral fringes in separated traces.%The features of an attosecond extreme ultraviolet (XUV) field are encoded in the attosecond XUV spectrogram. We investigate the effect of the temporal structures of attosecond XUV fields on the attosecond streaking spectrogram. Factors such as the number of attosecond XUV pulses and the temporal chirp of attosecond XUV pulses are considered. Results indicate that unlike the attosecond streaking spectrogram for an attosecond XUV field with two pulses of a half-cycle separation of streaking field, the spectrogram for the attosecond XUV field with three pulses demonstrates fine spectral fringes in separated traces.

  12. Electronic structures of melatonin and related compounds studied by photoelectron spectroscopy

    CERN Document Server

    Kubota, M

    2003-01-01

    Melatonin is a hormone structurally regarded as being composed of a 5-methoxyindole group and an N-ethylacetamide group; its various physiological activities have attracted a great deal of attention recently. The gas phase He(I) photoelectron spectra of melatonin (M) and its related compounds including N-acetylserotonin have been studied with the aid of molecular orbital calculations. The first photoelectron spectral band group of compound M is ascribed to ionizations from the two pi orbitals localized on the methoxyindole group. The second band group is quite complicated and is regarded as being composed of several bands. The lower energy part of the second band group is ascribed to the three orbitals relevant to the third highest occupied pi orbital of 5-methoxyindole and the highest occupied pi and the n sub C sub = sub 0 orbitals of N-ethylacetamide. The interactions among the three orbitals have been found to operate on the basis of the molecular orbital calculations; these interactions depend strongly o...

  13. Expansion dynamics of supercritical water probed by picosecond time-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Gladytz, Thomas; Abel, Bernd; Siefermann, Katrin R

    2015-02-21

    Vibrational excitation of liquid water with femtosecond laser pulses can create extreme states of water. Yet, the dynamics directly after initial sub-picosecond delocalization of molecular vibrations remain largely unclear. We study the ultrafast expansion dynamics of an accordingly prepared supercritical water phase with a picosecond time resolution. Our experimental setup combines vacuum-compatible liquid micro-jet technology and a table top High Harmonic light source driven by a femtosecond laser system. An ultrashort laser pulse centered at a wavelength of 2900 nm excites the OH-stretch vibration of water molecules in the liquid. The deposited energy corresponds to a supercritical phase with a temperature of about 1000 K and a pressure of more than 1 GPa. We use a time-delayed extreme ultraviolet pulse centered at 38.6 eV, and obtained via High Harmonic generation (HHG), to record valence band photoelectron spectra of the expanding water sample. The series of photoelectron spectra is analyzed with noise-corrected target transform fitting (cTTF), a specifically developed multivariate method. Together with a simple fluid dynamics simulation, the following picture emerges: when a supercritical phase of water expands into vacuum, temperature and density of the first few nanometers of the expanding phase drop below the critical values within a few picoseconds. This results in a supersaturated phase, in which condensation seeds form and grow from small clusters to large clusters on a 100 picosecond timescale.

  14. A Study on the Structure and Photodetachment Dynamics of Copper Based Molecular Anions Using Photoelectron Spectroscopy

    Science.gov (United States)

    Holtgrewe, Nicholas Stephen

    This dissertation represents a study of the effects of electron molecule interactions in the detachment and dissociation dynamics of copper based molecular anions. Results are presented on the photodetachment of small copper oxide CuOn-- (n = 1, 2) and copper fluoride CuFn-- (n = 1, 2) molecular anions. Effects of different resonances are explored using the photoelectron angular distributions (PADs) and the relative intensity variations in vibrational channel cross sections. The specific resonances studied include dipole bound resonances, in which the electric dipole moment of the neutral molecule captures the outgoing electron, and electronic Feshbach resonances, in which the anion undergoes absorption to an excited anion state (lying energetically above the neutral) followed by relaxation via autodetachment into the electronic continuum. In addition to electron scattering resonances, the effects of dissociation dynamics on linear CuO2-- are studied, wherein the linear anion isomer was found to dissociate to Cu-- fragments. This dissociation process is interpreted with experimental data acquired from nanosecond photoelectron images and a femtosecond time resolved study.

  15. Electronic structures of melatonin and related compounds studied by photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kubota, Mari. E-mail: marik@hc.cc.keio.ac.jp; Kobayashi, Tsunetoshi

    2003-02-01

    Melatonin is a hormone structurally regarded as being composed of a 5-methoxyindole group and an N-ethylacetamide group; its various physiological activities have attracted a great deal of attention recently. The gas phase He(I) photoelectron spectra of melatonin (M) and its related compounds including N-acetylserotonin have been studied with the aid of molecular orbital calculations. The first photoelectron spectral band group of compound M is ascribed to ionizations from the two {pi} orbitals localized on the methoxyindole group. The second band group is quite complicated and is regarded as being composed of several bands. The lower energy part of the second band group is ascribed to the three orbitals relevant to the third highest occupied {pi} orbital of 5-methoxyindole and the highest occupied {pi} and the n{sub C=0} orbitals of N-ethylacetamide. The interactions among the three orbitals have been found to operate on the basis of the molecular orbital calculations; these interactions depend strongly on the conformations. The high energy end of the second band group is relevant to the {pi} orbital mainly localized on the 5-methoxyindole group and is ascribed to the fourth highest occupied {pi} orbital of 5-methoxyindole.

  16. Surface study of stainless steel electrode deposition from soil electrokinetic (EK) treatment using X-ray photoelectron spectroscopy (XPS)

    Energy Technology Data Exchange (ETDEWEB)

    Embong, Zaidi, E-mail: zaidi@uthm.edu.my [Faculty of Science, Technology and Human Development, Universiti Tun Hussien Onn Malaysia (UTHM) 86400, Parit Raja, Batu, Johor (Malaysia); Research Centre for Soft Soils (RECESS), Office for Research, Innovation, Commercialization and Consultancy Management (ORICC), Universiti Tun Hussien Onn Malaysia UTHM 86400, Parit Raja, Batu, Johor (Malaysia); Johar, Saffuwan [Faculty of Science, Technology and Human Development, Universiti Tun Hussien Onn Malaysia (UTHM) 86400, Parit Raja, Batu, Johor (Malaysia); Tajudin, Saiful Azhar Ahmad [Research Centre for Soft Soils (RECESS), Office for Research, Innovation, Commercialization and Consultancy Management (ORICC), Universiti Tun Hussien Onn Malaysia UTHM 86400, Parit Raja, Batu, Johor (Malaysia); Sahdan, Mohd Zainizan [Microelectronics and Nanotechnology Centre (MiNT-SRC), Office for Research, Innovation, Commercialization and Consultancy Management (ORICC), Universiti Tun Hussien Onn Malaysia UTHM 86400, Parit Raja, Batu, Johor (Malaysia)

    2015-04-29

    Electrokinetic (EK) remediation relies upon application of a low-intensity direct current through the soil between stainless steel electrodes that are divided into a cathode array and an anode array. This mobilizes charged species, causing ions and water to move toward the electrodes. Metal ions and positively charged organic compounds move toward the cathode. Anions such as chloride, fluoride, nitrate, and negatively charged organic compounds move toward the anode. Here, this remediation techniques lead to a formation of a deposition at the both cathode and anode surface that mainly contributed byanion and cation from the remediated soil. In this research, Renggam-Jerangau soil species (HaplicAcrisol + RhodicFerralsol) with a surveymeter reading of 38.0 ± 3.9 μR/hr has been investigation in order to study the mobility of the anion and cation under the influence electric field. Prior to the EK treatment, the elemental composition of the soil and the stainless steel electrode are measured using XRF analyses. Next, the soil sample is remediated at a constant electric potential of 30 V within an hour of treatment period. A surface study for the deposition layer of the cathode and anode using X-ray Photoelectron spectroscopy (XPS) revealed that a narrow photoelectron signal from oxygen O 1s, carbon, C 1s silica, Si 2p, aluminium, Al 2p and chromium, Cr 2p exhibited on the electrode surface and indicate that a different in photoelectron intensity for each element on both electrode surface. In this paper, the mechanism of Si{sup 2+} and Al{sup 2+} cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail.

  17. A combined photoelectron spectroscopy and relativistic ab initio studies of the electronic structures of UFO and UFO(-).

    Science.gov (United States)

    Roy, Soumendra K; Jian, Tian; Lopez, Gary V; Li, Wei-Li; Su, Jing; Bross, David H; Peterson, Kirk A; Wang, Lai-Sheng; Li, Jun

    2016-02-28

    The observation of the gaseous UFO(-) anion is reported, which is investigated using photoelectron spectroscopy and relativisitic ab initio calculations. Two strong photoelectron bands are observed at low binding energies due to electron detachment from the U-7sσ orbital. Numerous weak detachment bands are also observed due to the strongly correlated U-5f electrons. The electron affinity of UFO is measured to be 1.27(3) eV. High-level relativistic quantum chemical calculations have been carried out on the ground state and many low-lying excited states of UFO to help interpret the photoelectron spectra and understand the electronic structure of UFO. The ground state of UFO(-) is linear with an O-U-F structure and a (3)H4 spectral term derived from a U 7sσ(2)5fφ(1)5fδ(1) electron configuration, whereas the ground state of neutral UFO has a (4)H(7/2) spectral term with a U 7sσ(1)5fφ(1)5fδ(1) electron configuration. Strong electron correlation effects are found in both the anionic and neutral electronic configurations. In the UFO neutral, a high density of electronic states with strong configuration mixing is observed in most of the scalar relativistic and spin-orbit coupled states. The strong electron correlation, state mixing, and spin-orbit coupling of the electronic states make the excited states of UFO very challenging for accurate quantum chemical calculations.

  18. Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy.

    Science.gov (United States)

    Wilkinson, Iain; Boguslavskiy, Andrey E; Mikosch, Jochen; Bertrand, Julien B; Wörner, Hans Jakob; Villeneuve, David M; Spanner, Michael; Patchkovskii, Serguei; Stolow, Albert

    2014-05-28

    The excited state dynamics of isolated sulfur dioxide molecules have been investigated using the time-resolved photoelectron spectroscopy and time-resolved photoelectron-photoion coincidence techniques. Excited state wavepackets were prepared in the spectroscopically complex, electronically mixed (B̃)(1)B1/(Ã)(1)A2, Clements manifold following broadband excitation at a range of photon energies between 4.03 eV and 4.28 eV (308 nm and 290 nm, respectively). The resulting wavepacket dynamics were monitored using a multiphoton ionisation probe. The extensive literature associated with the Clements bands has been summarised and a detailed time domain description of the ultrafast relaxation pathways occurring from the optically bright (B̃)(1)B1 diabatic state is presented. Signatures of the oscillatory motion on the (B̃)(1)B1/(Ã)(1)A2 lower adiabatic surface responsible for the Clements band structure were observed. The recorded spectra also indicate that a component of the excited state wavepacket undergoes intersystem crossing from the Clements manifold to the underlying triplet states on a sub-picosecond time scale. Photoelectron signal growth time constants have been predominantly associated with intersystem crossing to the (c̃)(3)B2 state and were measured to vary between 750 and 150 fs over the implemented pump photon energy range. Additionally, pump beam intensity studies were performed. These experiments highlighted parallel relaxation processes that occurred at the one- and two-pump-photon levels of excitation on similar time scales, obscuring the Clements band dynamics when high pump beam intensities were implemented. Hence, the Clements band dynamics may be difficult to disentangle from higher order processes when ultrashort laser pulses and less-differential probe techniques are implemented.

  19. Attosecond streaking measurement of extreme ultraviolet pulses using a long-wavelength electric field

    Science.gov (United States)

    Saito, Nariyuki; Ishii, Nobuhisa; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

    2016-01-01

    Long-wavelength lasers have great potential to become a new-generation drive laser for tabletop coherent light sources in the soft X-ray region. Because of the significantly low conversion efficiency from a long-wavelength light field to high-order harmonics, their pulse characterization has been carried out by measuring the carrier-envelope phase and/or spatial dependences of high harmonic spectra. However, these photon detection schemes, in general, have difficulty in obtaining information on the spectral phases, which is crucial to determine the temporal structures of high-order harmonics. Here, we report the first attosecond streaking measurement of high harmonics generated by few-cycle optical pulses at 1.7 μm from a BiB3O6–based optical parametric chirped-pulse amplifier. This is also the first demonstration of time-resolved photoelectron spectroscopy using high harmonics from a long-wavelength drive laser other than Ti:sapphire lasers, which paves the way towards ultrafast soft X-ray photoelectron spectroscopy. PMID:27752115

  20. Attosecond streaking measurement of extreme ultraviolet pulses using a long-wavelength electric field

    Science.gov (United States)

    Saito, Nariyuki; Ishii, Nobuhisa; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

    2016-10-01

    Long-wavelength lasers have great potential to become a new-generation drive laser for tabletop coherent light sources in the soft X-ray region. Because of the significantly low conversion efficiency from a long-wavelength light field to high-order harmonics, their pulse characterization has been carried out by measuring the carrier-envelope phase and/or spatial dependences of high harmonic spectra. However, these photon detection schemes, in general, have difficulty in obtaining information on the spectral phases, which is crucial to determine the temporal structures of high-order harmonics. Here, we report the first attosecond streaking measurement of high harmonics generated by few-cycle optical pulses at 1.7 μm from a BiB3O6-based optical parametric chirped-pulse amplifier. This is also the first demonstration of time-resolved photoelectron spectroscopy using high harmonics from a long-wavelength drive laser other than Ti:sapphire lasers, which paves the way towards ultrafast soft X-ray photoelectron spectroscopy.

  1. First stages of surface steel nitriding: X-ray photoelectron spectroscopy and electrical measurements

    Energy Technology Data Exchange (ETDEWEB)

    Flori, M., E-mail: flori.mihaela@fih.upt.ro [' Politehnica' University of Timisoara, Faculty of Engineering of Hunedoara, 331128 Hunedoara (Romania); Gruzza, B.; Bideux, L.; Monier, G.; Robert-Goumet, C. [LASMEA, UMR CNRS 6602, Blaise Pascal University, 63177 Aubiere Cedex (France); Benamara, Z. [Laboratoire de Microelectronique Appliquee, Sidi Bel Abbes University, 22000 Sidi Bel Abbes (Algeria)

    2009-08-30

    Quantitative and qualitative analysis techniques were employed to study the first stages of ultra-high vacuum plasma nitriding of the 42CrMo4 steel. At constant treatment temperature, maintained for all samples at about 360 deg. C, we have established the influence of treatment time on the chemical composition, thickness and electrical properties of the nitrided layer. In this purpose it was used a stacking atomic layer model describing the sample surface, which takes into account the attenuation depth of photoelectrons by the atomic monolayers. So, we have found that after 2 h of nitriding in laboratory conditions, 70% of the nitrided layer was composed of iron oxide. Also, I-V measurements indicate an influence of the nitride overlayer with increasing treatment time.

  2. HeI photoelectron spectroscopy of the isoproxy (CH 3) 2CHO radical

    Science.gov (United States)

    Zheng, Sun; Shijun, Zheng; Lingpeng, Meng; Dianxun, Wang

    2003-02-01

    A continuous (CH 3) 2CHO radical beam is generated by pyrolysis of (CH 3) 2CHONO at 145(±0.5) °C. The HeI photoelectron spectrum of (CH 3) 2CHO is recorded in situ. The IP of (CH 3) 2CHO is 9.70 eV and the spectrum of the X3A″ state of (CH 3) 2CHO + exhibits a vibrational progression of 1200±60 cm-1. The removal of an electron from the highest occupied molecular orbital 11a ', which corresponds to ionization process of ( CH3) 2CHO+( 1A')←( CH3) 2CHO( X2A') , leads to a very sharp peak at 10.21 eV. This study provides new experimental and theoretical ionization energies of several ionic states of (CH 3) 2CHO.

  3. Photoelectron spectroscopy and theoretical studies of gaseous uranium hexachlorides in different oxidation states: UCl6q- (q = 0-2)

    Science.gov (United States)

    Su, Jing; Dau, Phuong D.; Liu, Hong-Tao; Huang, Dao-Ling; Wei, Fan; Schwarz, W. H. E.; Li, Jun; Wang, Lai-Sheng

    2015-04-01

    Uranium chlorides are important in actinide chemistry and nuclear industries, but their chemical bonding and many physical and chemical properties are not well understood yet. Here, we report the first experimental observation of two gaseous uranium hexachloride anions, UCl6- and UCl62-, which are probed by photoelectron spectroscopy in conjunction with quantum chemistry calculations. The electron affinity of UCl6 is measured for the first time as +5.3 eV; its second electron affinity is measured to be +0.60 eV from the photoelectron spectra of UCl62-. We observe that the detachment cross sections of the 5f electrons are extremely weak in the visible and UV energy ranges. It is found that the one-electron one-determinental molecular orbital picture and Koopmans' theorem break down for the strongly internally correlated U-5f2 valence shell of tetravalent U+4 in UCl62-. The calculated adiabatic and vertical electron detachment energies from ab initio calculations agree well with the experimental observations. Electronic structure and chemical bonding in the uranium hexachloride species UCl62- to UCl6 are discussed as a function of the oxidation state of U.

  4. In-situ observation of oxidation of Ti(0001) surface by real-time photoelectron spectroscopy using synchrotron radiation

    CERN Document Server

    Takakuwa, Y; Yoshigoe, A; Teraoka, Y; Mizuno, Y; Tonda, H; Homma, T

    2003-01-01

    Temperature dependence of the initial oxidation kinetics of Ti(0001) surface was investigated by low energy electron diffraction (LEED) and real-time photoelectron spectroscopy using synchrotron radiation of surface- and bulk-sensitive photon energies. LEED observation revealed that oxide layers grow epitaxially with different surface structures depending on temperature: 1x1 at 200degC and sq root 3 x sq root 3 at 400degC. From the oxygen uptake curve measured by O 1s photo-electron intensity, it was clarified that oxygen diffusion through the epitaxially grown oxide layer is significantly enhanced with raising temperature, making the oxide layer thicker than 70A at 400degC. The chemical shift components observed for Ti 2p showed that TiO sub 2 becomes predominant at the subsurface with O sub 2 dose, while the stoichiometry of oxide near the interface is maintained as TiO and Ti sub 2 O sub 3 , for both cases at 200degC and 400degC. Thus it is concluded that the epitaxial growth of a very thin oxide on the Ti...

  5. Route to One Atomic Unit of Time: Development of a Broadband Attosecond Streak Camera

    Science.gov (United States)

    Zhao, Kun; Zhang, Qi; Chini, Michael; Chang, Zenghu

    A new attosecond streak camera based on a three-meter-long magnetic-bottle time-of-flight electron spectrometer (MBES) is developed. The temporal resolution of the photoelectron detection system is measured to be better than 250 ps, which is sufficient to achieve an energy resolution of 0.5 eV at 150 eV photoelectron energy. In preliminary experiments, a 94-as isolated XUV pulse was generated and characterized. With a new algorithm to retrieve the amplitude and phase of XUV pulses (PROOF—phase retrieval by omega oscillation filtering), the attosecond streak camera will be able to characterize isolated attosecond pulses as short as one atomic unit of time (25 as).

  6. Investigation of interface dipole formation of dithiocarbamate molecules on gold by density functional theory and photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Tobias; Schulz, Philip; Meyer, Dominik; Wuttig, Matthias [I. Physikalisches Institut, RWTH Aachen University (Germany); Mazzarello, Riccardo [Institut fuer Theoretische Physik C, RWTH Aachen University (Germany)

    2011-07-01

    One of the main challenges in constructing organic optoelectronic devices is to control the charge carrier injection between the active organic material and metal contact electrodes. The insertion of a self assembled monolayer (SAM) between the organic/inorganic interface depicts an advantageous way to align the metal work function to the frontier molecular orbitals of adjacent organic species. In this study Dithiocarbamate terminated molecules (DTC) on gold have been investigated as a potential SAM building block. Photoelectron Spectroscopy reveals a strong lowering of the metal work function upon adsorption of DTC molecules. Hence, calculations employing density functional theory (DFT) have been conducted in order to correlate this effect to the formation of a layer of permanent as well as induced dipoles.

  7. X-ray Photoelectron Spectroscopy Study of Disordering in Gd2(Ti1-xZrx)2O7 Pyrochlores

    Science.gov (United States)

    Chen, J.; Lian, J.; Wang, L. M.; Ewing, R. C.; Wang, R. G.; Pan, W.

    2002-03-01

    The dramatic increases in ionic conductivity in Gd2(Ti1-xZrx)2O7 solid solution are related to disordering on the cation and anion lattices. Disordering in Gd2(Ti1-xZrx)2O7 was characterized using x-ray photoelectron spectroscopy (XPS). As Zr substitutes for Ti in Gd2Ti2O7 to form Gd2(Ti1-xZrx)2O7 (0.25

  8. Electronic structure of Al- and Ga-doped ZnO films studied by hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gabás, M.; Ramos Barrado, José R. [Lab. de Materiales and Superficies, Dpto. de Física Aplicada I, Universidad de Málaga, 29071 Málaga (Spain); Torelli, P. [Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, I-34149 Trieste (Italy); Barrett, N. T. [CEA, DSM/IRAMIS/SPCSI, F-91191 Gif-sur-Yvette Cedex (France); Sacchi, M. [Synchrotron SOLEIL, BP 48, 91192 Gif-sur-Yvette, France and Institut des NanoSciences de Paris, UPMC Paris 06, CNRS UMR 7588, 4 Place Jussieu, 75005 Paris (France)

    2014-01-01

    Al- and Ga-doped sputtered ZnO films (AZO, GZO) are semiconducting and metallic, respectively, despite the same electronic valence structure of the dopants. Using hard X-ray photoelectron spectroscopy we observe that both dopants induce a band in the electronic structure near the Fermi level, accompanied by a narrowing of the Zn 3d/O 2p gap in the valence band and, in the case of GZO, a substantial shift in the Zn 3d. Ga occupies substitutional sites, whereas Al dopants are in both substitutional and interstitial sites. The latter could induce O and Zn defects, which act as acceptors explaining the semiconducting character of AZO and the lack of variation in the optical gap. By contrast, mainly substitutional doping is consistent with the metallic-like behavior of GZO.

  9. Combined use of atomic force microscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry for cell surface analysis.

    Science.gov (United States)

    Dague, Etienne; Delcorte, Arnaud; Latgé, Jean-Paul; Dufrêne, Yves F

    2008-04-01

    Understanding the surface properties of microbial cells is a major challenge of current microbiological research and a key to efficiently exploit them in biotechnology. Here, we used three advanced surface analysis techniques with different sensitivity, probing depth, and lateral resolution, that is, in situ atomic force microscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry, to gain insight into the surface properties of the conidia of the human fungal pathogen Aspergillus fumigatus. We show that the native ultrastructure, surface protein and polysaccharide concentrations, and amino acid composition of three mutants affected in hydrophobin production are markedly different from those of the wild-type, thereby providing novel insight into the cell wall architecture of A. fumigatus. The results demonstrate the power of using multiple complementary techniques for probing microbial cell surfaces.

  10. X-ray Photoelectron Spectroscopy (XPS Depth Profiling for Evaluation of La2Zr2O7 Buffer Layer Capacity

    Directory of Open Access Journals (Sweden)

    Isabel van Driessche

    2012-02-01

    Full Text Available Lanthanum zirconate (LZO films from water-based precursors were deposited on Ni-5%W tape by chemical solution deposition. The buffer capacity of these layers includes the prevention of Ni oxidation of the substrate and Ni penetration towards the YBCO film which is detrimental for the superconducting properties. X-ray Photoelectron Spectroscopy depth profiling was used to study the barrier efficiency before and after an additional oxygen annealing step, which simulates the thermal treatment for YBCO thin film synthesis. Measurements revealed that the thermal treatment in presence of oxygen could severely increase Ni diffusion. Nonetheless it was shown that from the water-based precursors’ buffer layers with sufficient barrier capacity towards Ni penetration could be synthesized if the layers meet a certain critical thickness and density.

  11. Employing X-ray Photoelectron Spectroscopy for Determining Layer Homogeneity in Mixed Polar Self-Assembled Monolayers.

    Science.gov (United States)

    Hehn, Iris; Schuster, Swen; Wächter, Tobias; Abu-Husein, Tarek; Terfort, Andreas; Zharnikov, Michael; Zojer, Egbert

    2016-08-04

    Self-assembled monolayers (SAMs) containing embedded dipolar groups offer the particular advantage of changing the electronic properties of a surface without affecting the SAM-ambient interface. Here we show that such systems can also be used for continuously tuning metal work functions by growing mixed monolayers consisting of molecules with different orientations of the embedded dipolar groups. To avoid injection hot-spots when using the SAM-modified electrodes in devices, a homogeneous mixing of the two components is crucial. We show that a combination of high-resolution X-ray photoelectron spectroscopy with state-of-the-art simulations is an ideal tool for probing the electrostatic homogeneity of the layers and thus for determining phase separation processes in polar adsorbate assemblies down to inhomogeneities at the molecular level.

  12. X-ray photoelectron spectroscopy as a probe of the interaction between rhodium acetate and ionic liquids

    Science.gov (United States)

    Men, Shuang; Jiang, Jing

    2016-02-01

    X-ray photoelectron spectroscopy (XPS) is used as a probe of the interaction between rhodium acetate ([Rh2(OAc)4]) and ionic liquids. Due to the impact of the anion of ionic liquids on the electronic environment of the rhodium centre, the measured Rh 3d binding energies of [Rh2(OAc)4] dissolved in a series of ionic liquids were found to decrease along with the increasing of the basicity of anions. The reduction of Rh(II) to Rh(0) in 1-octyl-3methylimidazolium acetate ([C8C1Im][OAc]) under UHV condition was monitored by XPS. The intensity of the new formed metallic Rh(0) peak was found increased along with time. The surface enrichment of the new formed Rh(0) species in the system was also concluded.

  13. Single-State Electronic Structure Measurements Using Time-Resolved X-Ray Laser Induced Photoelectron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A J; Dunn, J; van Buuren, T; Hunter, J

    2004-11-11

    We demonstrate single-shot x-ray laser induced time-of-flight photoelectron spectroscopy on semiconductor and metal surfaces with picosecond time resolution. The LLNL COMET compact tabletop x-ray laser source provides the necessary high photon flux (>10{sup 12}/pulse), monochromaticity, picosecond pulse duration, and coherence for probing ultrafast changes in the city, chemical and electronic structure of these materials. Static valence band and shallow core-level photoemission spectra are presented for ambient temperature Ge(100) and polycrystalline Cu foils. Surface contamination was removed by UV ozone cleaning prior to analysis. In addition, the ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials. Time-resolved electron time-of-flight photoemission results for ultra-thin Cu will be presented.

  14. Thermodynamic equilibrium studies of nanocrystallite SrTiO3 grain boundaries by high temperature photoelectron spectroscopy

    Institute of Scientific and Technical Information of China (English)

    刘振祥; 谢侃

    2000-01-01

    Nanostructured strontium titanate (SrTiO3) thin films are studied by high temperature pho-toelectron spectroscopy and thermal gravimetric analysis. The results indicate that ion migration and redistribution as well as transformation between lattice oxygen and gas phase oxygen take place near the grain boundaries during thermodynamic equilibrium process, which lead to obvious variation of the surface composition with temperature. The lattice oxygen ions migrate from bulk to grain surface with temperature rising up; meanwhile Ti ions also migrate to grain surface and combine with oxygen ions forming Ti-O complex. An opposite process takes place during temperature falling down, but the latter process is much slower than the former one. A primary model is proposed to explain this phenomenon.

  15. Thermodynamic equilibrium studies of nanocrystallite SrTiO3 grain boundaries by high temperature photoelectron spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Nanostructured strontium titanate (SrTiO3) thin films are studied by high temperature photoelectron spectroscopy and thermal gravimetric analysis. The results indicate that ion migration and redistribution as well as transformation between lattice oxygen and gas phase oxygen take place near the grain boundaries during thermodynamic equilibrium process, which lead to obvious variation of the surface composition with temperature. The lattice oxygen ions migrate from bulk to grain surface with temperature rising up; meanwhile Ti ions also migrate to grain surface and combine with oxygen ions forming Ti-O complex. An opposite process takes place during temperature falling down, but the latter process is much slower than the former one. A primary model is proposed to explain this phenomenon.

  16. Light-induced changes in an alkali metal atomic vapor cell coating studied by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hibberd, A. M.; Bernasek, S. L. [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States); Seltzer, S. J. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Balabas, M. V. [Department of Physics, Saint-Petersburg State University, St. Petersburg 198504 (Russian Federation); Morse, M. [Department of Materials Science Engineering, Boise State University, Boise, Idaho 83725 (United States); Budker, D. [Department of Physics, University of California, Berkeley, California 94720-7300 (United States); Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2013-09-07

    The light-induced desorption of Rb atoms from a paraffin coating is studied with depth-profiling X-ray photoelectron spectroscopy (XPS) using tunable synchrotron radiation. Following Rb exposure, shifts of the C1s signal to higher binding energies, as well as the appearance of lower binding energy components in the O1s region, were observed. These effects were diminished after irradiation with desorbing light. Additionally, following desorbing-light irradiation, changes in the depth-dependent concentration of carbon were observed. These observations offer an insight into the microscopic changes that occur during light-induced atomic desorption and demonstrate the utility of XPS in understanding atom-coating interactions.

  17. The X-ray photoelectron spectroscopy depth profiling and tribological characterization of ion-plated gold on various metals

    Science.gov (United States)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1983-01-01

    For the case of ion-plated gold, the graded interface between gold and a nickel substrate and a nickel substrate, such tribological properties as friction and microhardness are examined by means of X-ray photoelectron spectroscopy analysis and depth profiling. Sliding was conducted against SiC pins in both the adhesive process, where friction arises from adhesion between sliding surfaces, and abrasion, in which friction is due to pin indentation and groove-plowing. Both types of friction are influenced by coating depth, but with opposite trends: the graded interface exhibited the highest adhesion, but the lowest abrasion. The coefficient of friction due to abrasion is inversely related to hardness. Graded interface microhardness values are found to be the highest, due to an alloying effect. There is almost no interface gradation between the vapor-deposited gold film and the substrate.

  18. Adsorption of ethylene on Sn and In terminated Si(001) surface studied by photoelectron spectroscopy and scanning tunneling microscopy

    Science.gov (United States)

    Zimmermann, Petr; Sobotík, Pavel; Kocán, Pavel; Ošt'ádal, Ivan; Vorokhta, Mykhailo; Acres, Robert George; Matolín, Vladimír

    2016-09-01

    Interaction of ethylene (C2H4) with Si(001)-Sn-2 × 2 and Si(001)-In-2 × 2 at room temperature has been studied using core level (C 1s) X-ray photoelectron spectroscopy with synchrotron radiation and scanning tunneling microscopy. Sn and In form similar dimer chains on Si(001)2 × 1, but exhibit different interaction with ethylene. While ethylene adsorbs on top of Sn dimers of the Si(001)-Sn-2 × 2 surface, the Si(001)-In-2 × 2 surface turned out to be inert. Furthermore, the reactivity of the Sn terminated surface is found to be considerably decreased in comparison with Si(001)2 × 1. According to the proposed adsorption model ethylene bonds to Sn dimers via [2 + 2] cycloaddition by interacting with their π dimer bonds. In contrast, indium dimers do not contain π bonds, which renders the In terminated Si(001) surface inert for ethylene adsorption.

  19. Adsorption of ethylene on Sn and In terminated Si(001) surface studied by photoelectron spectroscopy and scanning tunneling microscopy.

    Science.gov (United States)

    Zimmermann, Petr; Sobotík, Pavel; Kocán, Pavel; Ošt'ádal, Ivan; Vorokhta, Mykhailo; Acres, Robert George; Matolín, Vladimír

    2016-09-07

    Interaction of ethylene (C2H4) with Si(001)-Sn-2 × 2 and Si(001)-In-2 × 2 at room temperature has been studied using core level (C 1s) X-ray photoelectron spectroscopy with synchrotron radiation and scanning tunneling microscopy. Sn and In form similar dimer chains on Si(001)2 × 1, but exhibit different interaction with ethylene. While ethylene adsorbs on top of Sn dimers of the Si(001)-Sn-2 × 2 surface, the Si(001)-In-2 × 2 surface turned out to be inert. Furthermore, the reactivity of the Sn terminated surface is found to be considerably decreased in comparison with Si(001)2 × 1. According to the proposed adsorption model ethylene bonds to Sn dimers via [2 + 2] cycloaddition by interacting with their π dimer bonds. In contrast, indium dimers do not contain π bonds, which renders the In terminated Si(001) surface inert for ethylene adsorption.

  20. Electronic structure of Al- and Ga-doped ZnO films studied by hard X-ray photoelectron spectroscopy

    Directory of Open Access Journals (Sweden)

    M. Gabás

    2014-01-01

    Full Text Available Al- and Ga-doped sputtered ZnO films (AZO, GZO are semiconducting and metallic, respectively, despite the same electronic valence structure of the dopants. Using hard X-ray photoelectron spectroscopy we observe that both dopants induce a band in the electronic structure near the Fermi level, accompanied by a narrowing of the Zn 3d/O 2p gap in the valence band and, in the case of GZO, a substantial shift in the Zn 3d. Ga occupies substitutional sites, whereas Al dopants are in both substitutional and interstitial sites. The latter could induce O and Zn defects, which act as acceptors explaining the semiconducting character of AZO and the lack of variation in the optical gap. By contrast, mainly substitutional doping is consistent with the metallic-like behavior of GZO.

  1. Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Leo [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta (Canada); Nelson, Alan E. [Department of Chemical and Materials Engineering, University of Alberta (Canada)], E-mail: aenelson@dow.com; Heo, Giseon [Department of Statistics, Department of Dentistry, University of Alberta (Canada); Major, Paul W. [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta (Canada)

    2008-08-30

    The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found (p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength.

  2. Elemental content of enamel and dentin after bleaching of teeth (a comparative study between laser-induced breakdown spectroscopy and x-ray photoelectron spectroscopy)

    Energy Technology Data Exchange (ETDEWEB)

    Imam, H. [National Institute of Laser Enhanced Sciences, NILES, Cairo University, Giza (Egypt); Ahmed, Doaa [Department of Restorative Sciences, Faculty of Dentistry, Alexandria University, Alexandria (Egypt); Eldakrouri, Ashraf [National Institute of Laser Enhanced Sciences, NILES, Cairo University, Giza (Egypt); Department of Optometry and Vision Science, College of Applied Medical Science, King Saud University, Riyadh (Saudi Arabia)

    2013-06-21

    The elemental content of the superficial and inner enamel as well as that of dentin was analyzed using laser-induced breakdown spectroscopy (LIBS) and x-ray photoelectron spectroscopy (XPS) of bleached and unbleached tooth specimens. It is thus clear from the spectral analysis using both the LIBS and XPS technique that elemental changes (though insignificant within the scopes of this study) of variable intensities do occur on the surface of the enamel and extend deeper to reach dentin. The results of the LIBS revealed a slight reduction in the calcium levels in the bleached compared to the control specimens in all the different bleaching groups and in both enamel and dentin. The good correlation found between the LIBS and XPS results demonstrates the possibility of LIBS technique for detection of minor loss in calcium and phosphorus in enamel and dentin.

  3. High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe4O- and Fe5O-

    Science.gov (United States)

    Weichman, Marissa L.; DeVine, Jessalyn A.; Neumark, Daniel M.

    2016-08-01

    We report high-resolution photodetachment spectra of the cryogenically cooled iron monoxide clusters Fe4O- and Fe5O- obtained with slow photoelectron velocity-map imaging (cryo-SEVI). Well-resolved vibrational progressions are observed in both sets of spectra, and transitions to low-lying excited states of both species are seen. In order to identify the structural isomers, electronic states, and vibrational modes that contribute to the cryo-SEVI spectra of these clusters, experimental results are compared with density functional theory calculations and Franck-Condon simulations. The main bands observed in the SEVI spectra are assigned to the 15A2←16B2 photodetachment transition of Fe4O- and the 17A'←18A″ photodetachment transition of Fe5O-. We report electron affinities of 1.6980(3) eV for Fe4O and 1.8616(3) eV for Fe5O, although there is some uncertainty as to whether the 15A2 state is the true ground state of Fe4O. The iron atoms have a distorted tetrahedral geometry in Fe4O0/- and a distorted trigonal-bipyramidal arrangement in Fe5O0/-. For both neutral and anionic species, the oxygen atom preferably binds in a μ2-oxo configuration along the cluster edge. This finding is in contrast to prior predictions that Fe5O0/- exhibits a μ3 face-bound structure.

  4. Silica-supported silicotungstic acid: A study by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Berry, Frank J.; Derrick, Glyn R. [Department of Chemistry and Analytical Sciences, Robert Hooke Building, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); Marco, Jose F. [Instituto de Quimica -Fisica ' Rocasolano' , Consejo Superior de Investigaciones Cientificas, Serrano 119, 28006 Madrid (Spain); Mortimer, Michael [Department of Chemistry and Analytical Sciences, Robert Hooke Building, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom)], E-mail: m.mortimer@open.ac.uk

    2009-04-15

    W 4f and O 1s X-ray photoelectron spectra for silicotungstic acid, H{sub 4}SiW{sub 12}O{sub 40}, in pure and silica-supported form are reported. W 4f XP spectra for the supported acid are analysed in terms of contributions from two W(VI) spin-orbit doublets arising from tungsten atoms in terminal W=O bonds some of which directly interact with the silica surface. At low loading (3.2 wt.%) significant changes in the relative contributions and binding energies of the two spin-orbit doublets are taken as evidence of a strong interaction of individual [SiW{sub 12}O{sub 40}]{sup 4-} anions with highly active sites on the silica surface. It is suggested that selective ordering of silanol groups can occur on the silica surface in order to accommodate the adsorption of individual [SiW{sub 12}O{sub 40}]{sup 4-} anions.

  5. Tautomerism in 5-aminotetrazole investigated by core-level photoelectron spectroscopy and {Delta}SCF calculations

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, R.M., E-mail: ruipinto@fct.unl.pt [CFA, Centro de Fisica Atomica, Departamento de Fisica, Faculdade de Ciencias e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Dias, A.A. [CFA, Centro de Fisica Atomica, Departamento de Fisica, Faculdade de Ciencias e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Coreno, M. [CNR-IMIP, Montelibretti, Rome I-00016 (Italy); Simone, M. de [CNR-IOM, Laboratorio TASC, 34149 Trieste (Italy); Giuliano, B.M. [Departamento de Quimica da Universidade de Coimbra, 3004-535 Coimbra (Portugal); Santos, J.P.; Costa, M.L. [CFA, Centro de Fisica Atomica, Departamento de Fisica, Faculdade de Ciencias e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer High-resolution XPS of 5-aminotetrazole reveals different tautomers. Black-Right-Pointing-Pointer 5ATZ exists mainly in the 2H-form. Black-Right-Pointing-Pointer Results obtained with DSCF are in good agreement with the observed binding energies. - Abstract: The C 1s and N 1s photoelectron spectra of gas-phase 5-aminotetrazole (5ATZ) were recorded using synchrotron radiation, with the aim of evaluating 1H/2H tautomer population ratios. The core-electron binding energies (CEBEs) were estimated from computational results, using the delta self-consistent-field ({Delta}SCF) approach. Simulated spectra were generated using these CEBEs and the results from GAUSSIAN-n (Gn, n = 1, 2 and 3) and Complete Basis Set (CBS-4M and CBS-Q) methods. Results reveal the almost exclusive predominance of the 2H-tautomer, with a 1H/2H ratio of ca. 0.12/0.88, taken from a gross analysis of the XPS C 1s spectrum, recorded at 365 K.

  6. Multiphoton Processes and Attosecond Physics

    CERN Document Server

    Midorikawa, Katsumi; 12th International Conference on Multiphoton Processes; 3rd International Conference on Attosecond Physics

    2012-01-01

    Recent advances in ultrashort pulsed laser technology have opened new frontiers in atomic, molecular and optical sciences. The 12th International Conference on Multiphoton Processes (ICOMP12) and the 3rd International Conference on Attosecond Physics (ATTO3), held jointly in Sapporo, Japan, during July 3-8, showcased studies at the forefront of research on multiphoton processes and attosecond physics. This book summarizes presentations and discussions from these two conferences.

  7. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  8. Hydration of potassium iodide dimer studied by photoelectron spectroscopy and ab initio calculations

    Science.gov (United States)

    Li, Ren-Zhong; Zeng, Zhen; Hou, Gao-Lei; Xu, Hong-Guang; Zhao, Xiang; Gao, Yi Qin; Zheng, Wei-Jun

    2016-11-01

    We measured the photoelectron spectra of (KI)2-(H2O)n (n = 0-3) and conducted ab initio calculations on (KI)2-(H2O)n anions and their corresponding neutrals up to n = 6. Two types of spectral features are observed in the experimental spectra of (KI)2-(H2O) and (KI)2-(H2O)2, indicating that two types of isomers coexist, in which the high EBE feature corresponds to the hydrated chain-like (KI)2- while the low EBE feature corresponds to the hydrated pyramidal (KI)2-. In (KI)2-(H2O)3, the (KI)2- unit prefers a pyramidal configuration, and one of the K-I distances is elongated significantly, thus a K atom is firstly separated out from the (KI)2- unit. As for the neutrals, the bare (KI)2 has a rhombus structure, and the structures of (KI)2(H2O)n are evolved from the rhombus (KI)2 unit by the addition of H2O. When the number of water molecules reaches 4, the K-I distances have significant increment and one of the I atoms prefers to leave the (KI)2 unit. The comparison of (KI)2(H2O)n and (NaI)2(H2O)n indicates that it is slightly more difficult to pry apart (KI)2 than (NaI)2 via hydration, which is in agreement with the lower solubility of KI compared to that of NaI.

  9. A Method for Distinguishing Attosecond Single Pulse from Attosecond Pulse Train

    Institute of Scientific and Technical Information of China (English)

    HUO Yi-Ping; ZENG Zhi-Nan; LI Ru-Xin; XU Zhi-Zhan

    2004-01-01

    @@ The driving laser field assisted attosecond soft-extreme-ultraviolet (XUV) photo-ionization was used successfully to measure the duration of the attosecond pulse based on the cross-correlation method. However, this method in principle cannot distinguish a single attosecond pulse from the attosecond pulse train. We propose a technique for directly distinguishing attosecond single pulse from attosecond pulse train based on the photo-ionization of atoms by attosecond XUV pulse in the presence of a two-colour strong laser pulse.

  10. EDITORIAL: Focus on Attosecond Physics

    Science.gov (United States)

    Bandrauk, André D.; Krausz, Ferenc; Starace, Anthony F.

    2008-02-01

    Investigations of light-matter interactions and motion in the microcosm have entered a new temporal regime, the regime of attosecond physics. It is a main 'spin-off' of strong field (i.e., intense laser) physics, in which nonperturbative effects are fundamental. Attosecond pulses open up new avenues for time-domain studies of multi-electron dynamics in atoms, molecules, plasmas, and solids on their natural, quantum mechanical time scale and at dimensions shorter than molecular and even atomic scales. These capabilities promise a revolution in our microscopic knowledge and understanding of matter. The recent development of intense, phase-stabilized femtosecond (10-15 s) lasers has allowed unparalleled temporal control of electrons from ionizing atoms, permitting for the first time the generation and measurement of isolated light pulses as well as trains of pulses on the attosecond (1 as = 10-18 s) time scale, the natural time scale of the electron itself (e.g., the orbital period of an electron in the ground state of the H atom is 152 as). This development is facilitating (and even catalyzing) a new class of ultrashort time domain studies in photobiology, photochemistry, and photophysics. These new coherent, sub-fs pulses carried at frequencies in the extreme ultraviolet and soft-x-ray spectral regions, along with their intense, synchronized near-infrared driver waveforms and novel metrology based on sub-fs control of electron-light interactions, are spawning the new science of attosecond physics, whose aims are to monitor, to visualize, and, ultimately, to control electrons on their own time and spatial scales, i.e., the attosecond time scale and the sub-nanometre (Ångstrom) spatial scale typical of atoms and molecules. Additional goals for experiment are to advance the enabling technologies for producing attosecond pulses at higher intensities and shorter durations. According to theoretical predictions, novel methods for intense attosecond pulse generation may in

  11. X-ray photoelectron spectroscopy and transmission electron microscopy analysis of silver-coated gold nanorods designed for bionanotechnology applications

    Science.gov (United States)

    Watanabe, Fumiya; Nima, Zeid A.; Honda, Takumi; Mitsuhara, Masatoshi; Nishida, Minoru; Biris, Alexandru S.

    2017-01-01

    Multicomponent nano-agents were designed and built via a core-shell approach to enhance their surface enhanced Raman scattering (SERS) signals. These nano-agents had 36 nm × 12 nm gold nanorod cores coated by 4 nm thick silver shell films and a subsequent thin bifunctional thiolated polyethylene glycol (HS-PEG-COOH) layer. Ambient time-lapsed SERS signal measurements of these functionalized nanorods taken over a two-week period indicated no signal degradation, suggesting that large portions of the silver shells remained in pure metallic form. The morphology of the nanorods was characterized by transmission electron microscopy (TEM) and ultra-high resolution scanning TEM. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were utilized to assess the oxidation states of the silver shells covered by HS-PEG-COOH. The binding energies of Ag 3d XPS spectra yielded very small chemical shifts with oxidation; however, the AES peak shapes gave meaningful information about the extent of oxidation undergone by the nano-agent. While the silver shells without HS-PEG-COOH coatings oxidized significantly, the silver shells with HS-PEG-COOH remained predominantly metallic. In fact, six month-old samples still retained mostly metallic silver shells. These findings further demonstrate the stability and longevity of the nanostructures, indicating their significant potential as plasmonically active agents for highly sensitive detection in various biological systems, including cancer cells, tissues, or even organisms.

  12. Band bending at copper and gold interfaces with ferroelectric Pb(Zr,Ti)O3 investigated by photoelectron spectroscopy

    Science.gov (United States)

    Apostol, Nicoleta G.; Ştoflea, Laura E.; Tănase, Liviu C.; Bucur, Ioana Cristina; Chirilă, Cristina; Negrea, Raluca F.; Teodorescu, Cristian M.

    2015-11-01

    Interfaces formed by gold and copper on single crystal layers of (0 0 1) PbZr0.2Ti0.8O3 (PZT) produced by pulsed laser deposition and exhibiting outwards polarization are analyzed by X-ray photoelectron spectroscopy. The stoichiometry of the layers reproduces reasonably that of the PZT target. The band bending occurring at the interface between PZT and the metals is investigated by analyzing the core level shifts as function on the metal deposition. It is found that for Au/PZT(0 0 1) the gold layer is not continuous and the observed band bendings can be attributed to a Schottky mechanism, whereas for Cu/PZT(0 0 1) the copper layer is continuous; in this latter case, the observed band bendings towards higher energies (lower binding energies) can be attributed to a concomitant bending due to the Schottky effect together with the disappearance of the initial bending due to the outwards polarization of the samples. Metal Pb is observed to segregate only in the case of Cu/PZT(0 0 1), therefore the surface self-reduction might also be connected to the presence of a metal with lower work function, which for larger coverage forms a continuous metal layer, able to provide electrons to the surface. High resolution transmission electron spectroscopy yielded the disappearance of the tetragonal distortion in the case of Cu/PZT(0 0 1), in line with the assumption of disappearance of the polarization-induced band bending.

  13. Adsorption, X-ray Diffraction, Photoelectron, and Atomic Emission Spectroscopy Benchmark Studies for the Eighth Industrial Fluid Properties Simulation Challenge*+

    Science.gov (United States)

    Ross, Richard B.; Aeschliman, David B.; Ahmad, Riaz; Brennan, John K.; Brostrom, Myles L.; Frankel, Kevin A.; Moore, Jonathan D.; Moore, Joshua D.; Mountain, Raymond D.; Poirier, Derrick M.; Thommes, Matthias; Shen, Vincent K.; Schultz, Nathan E.; Siderius, Daniel W.; Smith, Kenneth D.

    2016-01-01

    The primary goal of the eighth industrial fluid properties simulation challenge was to test the ability of molecular simulation methods to predict the adsorption of organic adsorbates in activated carbon materials. The challenge focused on the adsorption of perfluorohexane in the activated carbon standard BAM-P109 (Panne and Thünemann 2010). Entrants were challenged to predict the adsorption of perfluorohexane in the activated carbon at a temperature of 273 K and at relative pressures of 0.1, 0.3, and 0.6. The relative pressure (P/Po) is defined as that relative to the bulk saturation pressure predicted by the fluid model at a given temperature (273 K in this case). The predictions were judged by comparison to a set of experimentally determined values, which are published here for the first time and were not disclosed to the entrants prior to the challenge. Benchmark experimental studies, described herein, were also carried out and provided to entrants in order to aid in the development of new force fields and simulation methods to be employed in the challenge. These studies included argon, carbon dioxide, and water adsorption in the BAM-P109 activated carbon as well as X-ray diffraction, X-ray microtomography, photoelectron spectroscopy, and atomic emission spectroscopy studies of BAM-P109. Several concurrent studies were carried out for the BAM-P108 activated carbon (Panne and Thünemann 2010). These are included in the current manuscript for comparison. PMID:27840543

  14. X-Ray Photoelectron Spectroscopy and Reflection High Energy Electron Diffraction of Epitaxial Growth SiC on Si(100) Using C60 and Si

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-Fang; LIU Jin-Feng; XU Peng-Shou; PAN Hai-Bin

    2007-01-01

    The formation of silicon carbide upon deposition of C60 and Si on Si(100) surface at 850 ℃ is studied via x-ray photoelectron spectroscopy and reflection high energy electron diffraction (RHEED). The C 1s, O 1s and Si 2p core-level spectra and the RHEED patterns indicate the formation of 3C-SiC.

  15. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) and a modified Levenberg-Marquardt fit procedure: a new combination for modeling thin layers

    NARCIS (Netherlands)

    Aarnink, W.A.M.; Weishaupt, A.; Silfhout, van A.

    1990-01-01

    The combination of angle-resolved X-ray photoelectron spectroscopy (ARXPS) and a modified Levenberg-Marquardt (LM) fit procedure has been used to study a native oxide layer on a clean Si(100) substrate. Numerical calculations show that with an aperture of 3° or 9° of the electron analyser, the photo

  16. Hard X-ray PhotoElectron Spectroscopy of transition metal oxides: Bulk compounds and device-ready metal-oxide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Borgatti, F., E-mail: francesco.borgatti@cnr.it [Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Consiglio Nazionale delle Ricerche (CNR), via P. Gobetti 101, Bologna I-40129 (Italy); Torelli, P.; Panaccione, G. [Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, Trieste I-34149 (Italy)

    2016-04-15

    Highlights: • Hard X-ray PhotoElectron Spectroscopy (HAXPES) applied to buried interfaces of systems involving Transition Metal Oxides. • Enhanced contribution of the s states at high kinetic energies both for valence and core level spectra. • Sensitivity to chemical changes promoted by electric field across metal-oxide interfaces in resistive switching devices. - Abstract: Photoelectron spectroscopy is one of the most powerful tool to unravel the electronic structure of strongly correlated materials also thanks to the extremely large dynamic range in energy, coupled to high energy resolution that this form of spectroscopy covers. The kinetic energy range typically used for photoelectron experiments corresponds often to a strong surface sensitivity, and this turns out to be a disadvantage for the study of transition metal oxides, systems where structural and electronic reconstruction, different oxidation state, and electronic correlation may significantly vary at the surface. We report here selected Hard X-ray PhotoElectron Spectroscopy (HAXPES) results from transition metal oxides, and from buried interfaces, where we highlight some of the important features that such bulk sensitive technique brings in the analysis of electronic properties of the solids.

  17. An X-ray photoelectron spectroscopy study of the acidity of SiO{sub 2}-ZrO{sub 2} mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Bosman, H.J.M.; Pijpers, A.P.; Jaspers, A.W.M.A. [DSM Research B.V., MD Geleen (Netherlands)

    1996-07-01

    X-ray photoelectron spectroscopy (XPS) of SiO{sub 2}-ZrO{sub 2} mixed oxides was studied. Surface acidity was investigated in light of the relationship between acidity and catalytic effects. 28 refs., 12 figs., 3 tabs.

  18. An X-Ray Photoelectron Spectroscopy (XPS) Study of Activated Carbons Impregnated with Some Organocopper Complexes

    Science.gov (United States)

    1993-10-01

    organocuivre ont dte imprdgn~s & la surface du charbon activd, et la composition de la surface du charbon imprdgn6 a dt examinee par spectroscopie...F/Cu et du C/Cu a pu fitre calcule. Ii a dtd trouvd que trois de ces * complexes dtaient soit instables ou ddcomposds & la surface du charbon . Cette...surface composition analysis, there was actually a higher concentration of Cu(I) than Cu(II), the original impregnant. It has been mentioned in an

  19. Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Guorong [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Neville, Simon P.; Worth, Graham A., E-mail: g.a.worth@bham.ac.uk [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Schalk, Oliver [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 109 61 Stockholm (Sweden); Sekikawa, Taro [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Ashfold, Michael N. R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Stolow, Albert, E-mail: astolow@uottawa.ca [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Departments of Chemistry and Physics, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada)

    2015-02-21

    The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole’s electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A{sub 2}(πσ{sup ∗}) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A{sub 1}(ππ{sup ∗}) and B{sub 2}(ππ{sup ∗}) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole’s electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B{sub 1}(πσ{sup ∗}) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B{sub 1}(πσ{sup ∗}) state is found to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A{sub 2}(πσ{sup ∗}) state.

  20. Surface functional group characterization using chemical derivatization X-ray photoelectron spectroscopy (CD-XPS)

    Energy Technology Data Exchange (ETDEWEB)

    Jagst, Eda

    2011-03-18

    Chemical derivatization - X-ray photolectron spectroscopy (CD-XPS) was applied successfully in order to determine different functional groups on thin film surfaces. Different amino group carrying surfaces, prepared by spin coating, self-assembly and plasma polymerization, were successfully investigated by (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Amino groups were derivatized with the widely used primary amino group tags, pentafluorobenzaldehyde (PFB) and 4-(trifluoromethyl)-benzaldehyde (TFBA), prior to analysis. Primary amino group quantification was then carried out according to the spectroscopical data. Self-assembled monolayers (SAMs) of different terminal groups were prepared and investigated with XPS and spectra were compared with reference surfaces. An angle resolved NEXAFS measurement was applied to determine the orientation of SAMs. Plasma polymerized allylamine samples with different duty cycle, power and pressure values were prepared in order to study the effects of external plasma parameters on the primary amino group retention. CD-XPS was used to quantify the amino groups and experiments show, that the milder plasma conditions promote the retention of amino groups originating from the allylamine monomer. An interlaboratory comparison of OH group determination on plasma surfaces of polypropylene treated with oxygen plasma, was studied. The surfaces were investigated with XPS and the [OH] amount on the surfaces was calculated. (orig.)

  1. Probing the Vibrational Spectroscopy of the Deprotonated Thymine Radical by Photodetachment and State-Selective Autodetachment Photoelectron Spectroscopy via Dipole-Bound States

    Science.gov (United States)

    Huang, Dao-Ling; Zhu, Guo-Zhu; Wang, Lai-Sheng

    2016-06-01

    Deprotonated thymine can exist in two different forms, depending on which of its two N sites is deprotonated: N1[T-H]^- or N3[T-H]^-. Here we report a photodetachment study of the N1[T-H]^- isomer cooled in a cryogenic ion trap and the observation of an excited dipole-bound state. Eighteen vibrational levels of the dipole-bound state are observed, and its vibrational ground state is found to be 238 ± 5 wn below the detachment threshold of N1[T-H]^-. The electron affinity of the deprotonated thymine radical (N1[T-H]^.) is measured accruately to be 26 322 ± 5 wn (3.2635 ± 0.0006 eV). By tuning the detachment laser to the sixteen vibrational levels of the dipole-bound state that are above the detachment threshold, highly non-Franck-Condon resonant-enhanced photoelectron spectra are obtained due to state- and mode-selective vibrational autodetachment. Much richer vibrational information is obtained for the deprotonated thymine radical from the photodetachment and resonant-enhanced photoelectron spectroscopy. Eleven fundamental vibrational frequencies in the low-frequency regime are obtained for the N1[T-H]^. radical, including the two lowest-frequency internal rotational modes of the methyl group at 70 ± 8 wn and 92 ± 5 wn. D. L. Huang, H. T. Liu, C. G. Ning, G. Z. Zhu and L. S. Wang, Chem. Sci., 6, 3129-3138 (2015)

  2. Photoelectron Microscopy

    Science.gov (United States)

    King, Paul Lawrence

    1992-01-01

    This thesis describes the theory and first operations of a novel synchrotron-based imaging system allowing photoemission spectroscopy (XPS or ESCA) to be performed at lateral resolutions better than 10 microns. Originally developed in David Turner's group at Oxford, the MicroESCA^ {rm TM} relies on the diverging magnetic field from a 7 Tesla superconducting solenoid to project photoemitted electrons from a sample to an imaging detector located 1.5 meters away. The diverging magnetic field converts off-axis momentum to forward momentum and electrons form a magnified image at the detector while moving nearly parallel to one another. Because of this "parallelization", a planar gridded retarding field analyzer achieves excellent energy resolution with only minor impact on image quality. The thesis begins with an overview of the various techniques by which high lateral resolution photoelectron spectroscopy can be achieved. This is followed by a theoretical treatment of magnetic projection leading to predictions of lateral and energy resolution. Chapter 3 documents resolution tests and known deviations from ideality. Image forming capabilities and energy resolution of the retarding field analyzer are demonstrated at near-theoretical limits. Practical limitations of the microscope are recognized in the form of poor signal to noise ratios of core level images which originate from a combination of the narrow dynamic range of the imaging detector and the large backgrounds inherent in retarding field spectroscopy of solids. Chapter 4 describes an interactive image processing and interpretation scheme that relies on scatter plots and principal component analysis to reduce the dimensionality of retarding field image sets and improve image signal to noise. This procedure is generally applicable to all imaging spectroscopies and an example from SEM-based energy dispersive spectroscopy (EDS) is included. In a final results section, variations in the surface Fermi levels on cleaved

  3. X-ray photoelectron spectroscopy (XPS) and FTIR studies of vanadium barium phosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Majjane, Abdelilah [Laboratoire de Physico-Chimie des Matériaux Vitreux et Cristallisés, Université Ibn Tofail, Faculté des Sciences, Kénitra 14090 (Morocco); Chahine, Abdelkrim, E-mail: abdelkrimchahine@gmail.com [Laboratoire de Physico-Chimie des Matériaux Vitreux et Cristallisés, Université Ibn Tofail, Faculté des Sciences, Kénitra 14090 (Morocco); Et-tabirou, Mohamed [Laboratoire de Physico-Chimie des Matériaux Vitreux et Cristallisés, Université Ibn Tofail, Faculté des Sciences, Kénitra 14090 (Morocco); Echchahed, Bousselham [Laboratoire d' Electrochimie, Corrosion et Environnement, Université Ibn Tofail, Faculté des Sciences, Kénitra (Morocco); Do, Trong-On [Département de génie chimique, Université Laval, G1K 7P4 (Canada); Breen, Peter Mc [Département de chimie, Université Laval, G1K 7P4 (Canada)

    2014-01-15

    Barium vanadophosphate glasses, having composition 50BaO–xV{sub 2}O{sub 5}–(50 − x)P{sub 2}O{sub 5}, (x = 0–50 mol%), were prepared by conventional melt quench method. Density, molar volume and glass transition temperature (T{sub g}) were measured as a function of V{sub 2}O{sub 5} content. Structural investigation was done using XPS and FTIR spectroscopy. First, substitution of the P{sub 2}O{sub 5} by the V{sub 2}O{sub 5} in the metaphosphate 50BaO–50P{sub 2}O{sub 5} glass increases the density and T{sub g} and decreases the molar volume. When the amount of V{sub 2}O{sub 5} increases, all these properties show a reverse trend. XPS measurement found in the O1s, P2p, and V2p core level spectra indicate the presence of primarily P–O–P, P–O–V and V–O–V structural bonds, the asymmetry in the P 2p spectra indeed arises from the spin-orbit splitting of P 2p core level, and more than one valence state of V ions being present. IR spectroscopy reveals the depolymerization of the phosphate glass network by systematic conversion of metaphosphate chains into pyrophosphate groups and then orthophosphate groups. Even though metaphosphate to pyrophosphate conversion is taking place due to breaking of P–O–P linkages, formation of P–O–V and P–O–Ba linkages provide cross linking between short P-structural units, which make the glass network more rigid. Above 10–20 mol% V{sub 2}O{sub 5} content, network is highly depolymerized due to the formation of orthophosphate units and V–O–V bridge bonds, resulting in poor cross-linking, making the glass network less rigid. - Highlights: • Barium–vanadium–phosphate glasses. • Structure has been investigated by XPS and IR spectra. • Variation in structure and properties with substitution of V{sub 2}O{sub 5} for P{sub 2}O{sub 5}. • Conversion of metaphosphate to pyrophosphate and finally to orthophosphate. • Substitution of P–O–P linkages by P–O–V, P–O–Ba and V–O–V linkages.

  4. Quantitative Surface Analysis by Xps (X-Ray Photoelectron Spectroscopy: Application to Hydrotreating Catalysts

    Directory of Open Access Journals (Sweden)

    Beccat P.

    1999-07-01

    Full Text Available XPS is an ideal technique to provide the chemical composition of the extreme surface of solid materials, vastly applied to the study of catalysts. In this article, we will show that a quantitative approach, based upon fundamental expression of the XPS signal, has enabled us to obtain a consistent set of response factors for the elements of the periodic table. In-depth spadework has been necessary to know precisely the transmission function of the spectrometer used at IFP. The set of response factors obtained enables to perform, on a routine basis, a quantitative analysis with approximately 20% relative accuracy, which is quite acceptable for an analysis of such a nature. While using this quantitative approach, we have developed an analytical method specific to hydrotreating catalysts that allows obtaining the sulphiding degree of molybdenum quite reliably and reproducibly. The usage of this method is illustrated by two examples for which XPS spectroscopy has provided with information sufficiently accurate and quantitative to help understand the reactivity differences between certain MoS2/Al2O3 or NiMoS/Al2O3-type hydrotreating catalysts.

  5. Quantum-mechanical analysis of pulse reconstruction for a narrow bandwidth attosecond x-ray pulse

    Institute of Scientific and Technical Information of China (English)

    Ge Yu-Cheng

    2009-01-01

    The photoelectron energy spectra(PESs)excited by narrow bandwidth attosecond x-ray pulses in the presence of a few-cycle laser are quantum-mechanically calculated.Transfer equations are used to reconstruct the detailed temporal structure of an attosecond x-ray pulse directly from a measured PES.Theoretical analysis shows that the temporal uncertainties of the pulse reconstruction depend on the x-ray bandwidth.The procedure of pulse reconstruction is direct and simple without making any previous pulse assumption,data fitting analysis and time-resolved measurement of PESs.The temporal measurement range is half of a laser optical cycle.

  6. The Frontiers of Attosecond Physics

    Science.gov (United States)

    Doumy, G.; Wheeler, J.; Blaga, C.; Catoire, F.; Chirla, R.; Colosimo, P.; March, A. M.; Agostini, P.; Dimauro, L. F.

    2009-03-01

    The genesis of light pulses with attosecond (10-18 seconds) durations signifies a new frontier in time-resolved physics. The scientific importance is obvious: the time-scale necessary for probing the motion of an electron(s) in the ground state is attoseconds (atomic unit of time = 24 as). The availability of attosecond pulses would allow, for the first time, the study of the time-dependent dynamics of correlated electron systems by freezing the motion, in essence exploring the structure with ultra-fast snapshots, then following the subsequent evolution using pump-probe techniques. This paper examines the fundamental principles of attosecond formation by Fourier synthesis of a high harmonic comb and phase measurements using two-color techniques. Quantum control of the spectral phase, critical to attosecond formation, has its origin in the fundamental response of an atom to an intense electromagnetic field. We will interpret the laser-atom interaction using a semi-classical trajectory model.

  7. Anion Binding of One-, Two-, and Three-Armed Thiourea Receptors Examined via Photoelectron Spectroscopy and Quantum Computations

    Energy Technology Data Exchange (ETDEWEB)

    Beletskiy, Evgeny V.; Wang, Xue-Bin; Kass, Steven R.

    2016-10-27

    A benzene ring substituted with 1–3 thiourea containing arms (1–3) were examined by photoelectron spectroscopy and density functional theory computations. Their conjugate bases and chloride, acetate and dihydrogen phosphate anion clusters are reported. The resulting vertical and adiabatic detachment energies span from 3.93 – 5.82 eV (VDE) and 3.65 – 5.10 (ADE) for the deprotonated species and 4.88 – 5.97 eV (VDE) and 4.45 – 5.60 eV (ADE) for the anion complexes. These results reveal the stabilizing effects of multiple hydrogen bonds and anionic host-guest interactions in the gas phase. Previously measured equilibrium binding constants in aqueous dimethyl sulfoxide for all three thioureas (Org. Biolmol. Chem. 2015, 13, 2170-2176) are compared to the present results and cooperative binding is uniformly observed in the gas phase but only for one case (i.e., 3 • H2PO4–) in solution.

  8. Adsorption of Saliva Related Protein on Denture Materials: An X-Ray Photoelectron Spectroscopy and Quartz Crystal Microbalance Study

    Directory of Open Access Journals (Sweden)

    Akiko Miyake

    2016-01-01

    Full Text Available The aim of this study was to evaluate the difference in the adsorption behavior of different types of bovine salivary proteins on the PMMA and Ti QCM sensors are fabricated by spin-coating and sputtering onto bare QCM sensors by using QCM and X-ray photoelectron spectroscopy (XPS. SPM, XPS, and contact angle investigations were carried out to determine the chemical composition and surface wettability of the QCM surface. We discuss the quality of each sensor and evaluate the potential of the high-frequency QCM sensors by investigating the binding between the QCM sensor and the proteins albumin and mucin (a salivary-related protein. The SPM image showed a relatively homogeneous surface with nano-order roughness. The XPS survey spectra of the thin films coated on the sensors were similar to the binding energy of the characteristic spectra of PMMA and Ti. Additionally, the amount of salivary-related protein on the PMMA QCM sensor was higher than those on the Ti and Au QCM sensors. The difference of protein adsorption is proposed to be related to the wettability of each material. The PMMA and Ti QCM sensors are useful tools to study the adsorption and desorption of albumin and mucin on denture surfaces.

  9. In situ chemical state analysis of buried polymer/metal adhesive interface by hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, Kenichi, E-mail: ozawa.k.ab@m.titech.ac.jp [Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Kakubo, Takashi; Shimizu, Katsunori; Amino, Naoya [The Yokohama Rubber Co., Ltd., Oiwake, Hiratsuka 254-8601 (Japan); Mase, Kazuhiko [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan); Ikenaga, Eiji; Nakamura, Tetsuya; Kinoshita, Toyohiko; Oji, Hiroshi [Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Hyogo 679-5198 (Japan)

    2014-11-30

    Highlights: • Chemical state analysis of the buried rubber/brass interface is conducted by HAXPES. • Ultrathin rubber films are prepared on the brass surface by two methods. • A high density of Cu{sub 2}S is found on the rubber side of the buried adhesive layer. • The chemical states of the buried and exposed interfaces are compared. - Abstract: Chemical state analysis of adhesive interfaces is important to understand an adhesion mechanism between two different materials. Although photoelectron spectroscopy (PES) is an ideal tool for such an analysis, the adhesive interfaces must be exposed to the surface because PES is essentially a surface sensitive technique. However, an in situ observation is possible by hard X-ray PES (HAXPES) owing to its large probing depth. In the present study, HAXPES is applied to investigate the adhesive interface between rubber and brass without exposing the interface. It is demonstrated that copper sulfides formed at the buried rubber/brass interface are distinguished from S-containing species in the rubber overlayer. The chemical state of the buried interface is compared with that of the “exposed” interface prepared by so-called a filter-paper method.

  10. Photoelectric characteristics of silicon P—N junction with nanopillar texture: Analysis of X-ray photoelectron spectroscopy

    Science.gov (United States)

    Liu, Jing; Wang, Jia-Ou; Yi, Fu-Ting; Wu, Rui; Zhang, Nian; Ibrahim, Kurash

    2014-09-01

    Silicon nanopillars are fabricated by inductively coupled plasma (ICP) dry etching with the cesium chloride (CsCl) islands as masks originally from self-assembly. Wafers with nanopillar texture or planar surface are subjected to phosphorus (P) diffusion by liquid dopant source (POCl3) at 870 °C to form P—N junctions with a depth of 300 nm. The X-ray photoelectron spectroscopy (XPS) is used to measure the Si 2p core levels of P—N junction wafer with nanopillar texture and planar surface. With a visible light excitation, the P—N junction produces a new electric potential for photoelectric characteristic, which causes the Si 2p core level to have a energy shift compared with the spectrum without the visible light. The energy shift of the Si 2p core level is -0.27 eV for the planar P—N junction and -0.18 eV for the nanopillar one. The difference in Si 2p energy shift is due to more space lattice defects and chemical bond breaks for nanopillar compared with the planar one.

  11. Characterization of photocatalytic TiO2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

    Science.gov (United States)

    Krishnan, Padmaja; Liu, Minghui; Itty, Pierre A.; Liu, Zhi; Rheinheimer, Vanessa; Zhang, Min-Hong; Monteiro, Paulo J. M.; Yu, Liya E.

    2017-02-01

    Consecutive eight study phases under the successive presence and absence of UV irradiation, water vapor, and oxygen were conducted to characterize surface changes in the photocatalytic TiO2 powder using near-ambient-pressure X-ray photoelectron spectroscopy (XPS). Both Ti 2p and O 1s spectra show hysteresis through the experimental course. Under all the study environments, the bridging hydroxyl (OHbr) and terminal hydroxyl (OHt) are identified at 1.1–1.3 eV and 2.1–2.3 eV above lattice oxygen, respectively. This enables novel and complementary approach to characterize reactivity of TiO2 powder. The dynamic behavior of surface-bound water molecules under each study environment is identified, while maintaining a constant distance of 1.3 eV from the position of water vapor. In the dark, the continual supply of both water vapor and oxygen is the key factor retaining the activated state of the TiO2 powder for a time period. Two new surface peaks at 1.7–1.8 and 4.0–4.2 eV above lattice oxygen are designated as peroxides (OOH/H2O2) and H2O2 dissolved in water, respectively. The persistent peroxides on the powder further explain previously observed prolonged oxidation capability of TiO2 powder without light irradiation.

  12. Probing Co/Si interface behaviour by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM)

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this work, we investigate the Co-Si reaction, the Co growth mode at room temperature, diffusion behaviour as well as morphology evolution during annealing on both H-terminated and clean Si(001) and Si(111) surfaces. From in-situ X-ray photoelectron spectroscopy (XPS) investigation, "Co-Si" reaction appears to occur on both H-terminated and clean surfaces at room temperature (RT) and the silicide crystallinity is improved upon annealing.Co growth mode on H-terminated Si surfaces occurs in a pseudo layer-by-layer manner while small close-packed island growth mode is observed on the clean Si surface. Upon annealing at different temperatures, Co atom concentration decreases versus annealing time, which in part is attributed to Co atoms inward diffusion. The diffusion behaviour on both types of surfaces demonstrates a similar trend. Morphology study using ex-situ atomic force microscopy (AFM) shows that the islands formed on Si(001) surface after annealing at 700 ℃ are elongated with growth directions alternate between the two perpendicular [(-1)10] and [110] directions. Triangular islands are observed on Si(111) surface.

  13. Analysis of the surface of tricalcium silicate during the induction period by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bellmann, F., E-mail: frank.bellmann@uni-weimar.de [Institute for Building Materials Science, Bauhaus University Weimar, 99423 Weimar (Germany); Sowoidnich, T.; Ludwig, H.-M. [Institute for Building Materials Science, Bauhaus University Weimar, 99423 Weimar (Germany); Damidot, D. [Ecole des Mines de Douai, Civil and Environmental Engineering Department, 941 rue Charles Bourseul, BP 10838, 59508 Doua cedex (France)

    2012-09-15

    X-ray photoelectron spectroscopy allows the analysis of surface layers with a thickness of a few nanometers. The method is sensitive to the chemical environment of the atoms since the binding energy of the electrons depends on the chemical bonds to neighboring atoms. It has been applied to the hydration of tricalcium silicate (Ca{sub 3}SiO{sub 5}, C{sub 3}S) by analyzing a sample after 30 min of hydration. Also two references have been investigated namely anhydrous C{sub 3}S and intermediate phase in order to enable a quantitative evaluation of the experimental data. In the hydrated C{sub 3}S sample, the analyzed volume (0.2 mm{sup 2} surface by 13 nm depth) contained approximately 44 wt.% of C{sub 3}S and 56 wt.% of intermediate phase whereas C-S-H was not detected. Scanning Electron Microscopy data and geometric considerations indicate that the intermediate phase forms a thin layer having a thickness of approximately 2 nm and covers the complete surface instead of forming isolated clusters.

  14. X-ray photoelectron spectroscopy of cadmium tin oxide ceramics in as-fired and electrochemically reduced forms

    Energy Technology Data Exchange (ETDEWEB)

    Hashemi, T.; Illingsworth, J. (Applied Physics and Electronics, School of Engineering and Applied Science, Univ. of Durham, Durham DH1 3LE (GB)); Golestani-Fard, F. (Material and Energy Research Center, Tehran (IR))

    1991-03-01

    X-ray photoelectron spectroscopy (XPS) has been employed to investigate the chemical nature of samples of dicadmium stannate (Cd{sub 2}SnO{sub 4}) in the as-fired, electrochemically reduced, and reoxidized states. The reduction of Cd{sub 2}SnO{sub 4} was found to be associated with a dramatic color change from bright yellow to dark green, a phenomenon commonly known as the electrochromic effect. Both quantitative XPS results and binding energy measurements proved that, upon exposure of the reduced ceramic bodies to air, the Sn{sup 2+} to Sn{sup 4+} transition readily took place to produce the intermediate compound, Cd{sub 2}SnO{sub 3} with divalent tin. Prolonged exposure to the atmosphere did not result in further progress of reoxidation extending to monovalent cadmium. However, complete reoxidation of the reduced samples was possible by annealing in air at 350{degrees}C for a short period of time, e.g., 3 h by which the original features of the as-fired state such as color and electrical conductivity were restored. The results also showed that reoxidized samples at high temperature assume the same XPS characteristics as those of as-fired ceramics.

  15. Resonant photoelectron spectroscopy of γ-Al{sub 2}O{sub 3}/SrTiO{sub 3} heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schuetz, Philipp; Pfaff, Florian; Zapf, Michael; Gabel, Judith; Dudy, Lenart; Berner, Goetz; Sing, Michael; Claessen, Ralph [Wuerzburg Univ. (Germany). Physikalisches Inst. and Roentgen Center for Complex Material Systems (RCCM); Chen, Yunzhong; Pryds, Nini [Technical Univ. of Denmark, Risoe (Denmark). Dept. of Energy Conversion and Storage; Rogalev, Victor; Strocov, Vladimir [Paul Scherrer Institut, Villigen (Switzerland). Swiss Light Source; Schlueter, Christoph; Lee, Tien-Lin [Diamond Light Source Ltd., Didcot (United Kingdom)

    2015-07-01

    The spinel/perovskite heterointerface between the band insulators γ-Al{sub 2}O{sub 3} and SrTiO{sub 3} hosts a two-dimensional electron system (2DES) with exceptionally high electron mobility. Soft X-ray resonant photoelectron spectroscopy at the Ti L absorption edge is used to probe the Ti 3d derived interface states. Marked differences in the resonance behavior are found for the SrTiO{sub 3} valence band and the different interface states, which are observed in the band gap of SrTiO{sub 3}. A comparison to X-ray absorption spectra of Ti 3d{sup 0} and Ti 3d{sup 1} systems reveals the presence of different types of electronic states with Ti 3d character, i.e., oxygen vacancy induced, trapped in-gap states and itinerant states contributing to the 2DES. Furthermore, exposure to low doses of oxygen during irradiation allows for the controlled and reversible manipulation of the interfacial electronic structure, i.e., the in-gap state intensity and the valence band offset between SrTiO{sub 3} and γ-Al{sub 2}O{sub 3}.

  16. In situ x-ray photoelectron spectroscopy studies of gas/solidinterfaces at near-ambient conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bluhm, Hendrik; Havecker, Michael; Knop-Gericke, Axel; Kiskinova,Maya; Schlogl, Robert; Salmeron, Miquel

    2007-12-03

    X-ray photoelectron spectroscopy (XPS) is a quantitative, chemically specific technique with a probing depth of a few angstroms to a few nanometers. It is therefore ideally suited to investigate the chemical nature of the surfaces of catalysts. Because of the scattering of electrons by gas molecules, XPS is generally performed under vacuum conditions. However, for thermodynamic and/or kinetic reasons, the catalyst's chemical state observed under vacuum reaction conditions is not necessarily the same as that of a catalyst under realistic operating pressures. Therefore, investigations of catalysts should ideally be performed under reaction conditions, i.e., in the presence of a gas or gas mixtures. Using differentially pumped chambers separated by small apertures, XPS can operate at pressures of up to 1 Torr, and with a recently developed differentially pumped lens system, the pressure limit has been raised to about 10 Torr. Here, we describe the technical aspects of high-pressure XPS and discuss recent applications of this technique to oxidation and heterogeneous catalytic reactions on metal surfaces.

  17. Experimental determination of vacuum-level band alignments of SnS-based solar cells by photoelectron yield spectroscopy

    Science.gov (United States)

    Sugiyama, Mutsumi; Shimizu, Tsubasa; Kawade, Daisuke; Ramya, Kottadi; Ramakrishna Reddy, K. T.

    2014-02-01

    Energy band offsets of SnS-based solar cell structure using various n-type semiconductors, such as CdS, SnS2, In2S3, ZnIn2Se4, ZnO, and Mg0.3In0.7O, are evaluated by photoelectron yield spectroscopy. The valence band discontinuities are estimated to be 1.6 eV for both SnS/CdS and SnS/SnS2, 0.9 eV for SnS/In2S3, 1.7 eV for SnS/ZnIn2Se4, and 1.8 eV for both SnS/ZnO and SnS/Mg0.3Zn0.7O. Using the valence band discontinuity values and the corresponding energy bandgaps of the layers, energy band diagrams are developed. This study implied a type-I heterostructure, appropriate for SnS-based solar cell, for the ZnIn2Se4 or MgxZn1-xO (0 ≤ x ≤ 0.3) interface and type-II for other junctions.

  18. In-situ X-ray photoelectron spectroscopy studies of water on metals and oxides at ambient conditions

    Energy Technology Data Exchange (ETDEWEB)

    Salmeron, Miquel; Yamamoto, S.; Bluhm, H.; Andersson, K.; Ketteler, G.; Ogasawara, H.; Salmeron, M.; Nilsson, A.

    2007-10-29

    X-ray photoelectron spectroscopy (XPS) is a powerful tool for surface and interface analysis, providing the elemental composition of surfaces and the local chemical environment of adsorbed species. Conventional XPS experiments have been limited to ultrahigh vacuum (UHV) conditions due to a short mean free path of electrons in a gas phase. The recent advances in instrumentation coupled with third-generation synchrotron radiation sources enables in-situ XPS measurements at pressures above 5 Torr. In this review, we describe the basic design of the ambient pressure XPS setup that combines differential pumping with an electrostatic focusing. We present examples of the application of in-situ XPS to studies of water adsorption on the surface of metals and oxides including Cu(110), Cu(111), TiO2(110) under environmental conditions of water vapor pressure. On all these surfaces we observe a general trend where hydroxyl groups form first, followed by molecular water adsorption. The importance of surface OH groups and their hydrogen bonding to water molecules in water adsorption on surfaces is discussed in detail.

  19. Hard X-ray photoelectron and X-ray absorption spectroscopy characterization of oxidized surfaces of iron sulfides

    Science.gov (United States)

    Mikhlin, Yuri; Tomashevich, Yevgeny; Vorobyev, Sergey; Saikova, Svetlana; Romanchenko, Alexander; Félix, Roberto

    2016-11-01

    Hard X-ray photoelectron spectroscopy (HAXPES) using an excitation energy range of 2 keV to 6 keV in combination with Fe K- and S K-edge XANES, measured simultaneously in total electron (TEY) and partial fluorescence yield (PFY) modes, have been applied to study near-surface regions of natural polycrystalline pyrite FeS2 and pyrrhotite Fe1-xS before and after etching treatments in an acidic ferric chloride solution. It was found that the following near-surface regions are formed owing to the preferential release of iron from oxidized metal sulfide lattices: (i) a thin, no more than 1-4 nm in depth, outer layer containing polysulfide species, (ii) a layer exhibiting less pronounced stoichiometry deviations and low, if any, concentrations of polysulfide, the composition and dimensions of which vary for pyrite and pyrrhotite and depend on the chemical treatment, and (iii) an extended almost stoichiometric underlayer yielding modified TEY XANES spectra, probably, due to a higher content of defects. We suggest that the extended layered structure should heavily affect the near-surface electronic properties, and processes involving the surface and interfacial charge transfer.

  20. Uniqueness plots: A simple graphical tool for identifying poor peak fits in X-ray photoelectron spectroscopy

    Science.gov (United States)

    Singh, Bhupinder; Diwan, Anubhav; Jain, Varun; Herrera-Gomez, Alberto; Terry, Jeff; Linford, Matthew R.

    2016-11-01

    Peak fitting is an essential part of X-ray photoelectron spectroscopy (XPS) narrow scan analysis, and the Literature contains both good and bad examples of peak fitting. A common cause of poor peak fitting is the inclusion of too many fit parameters, often without a sound chemical and/or physical basis for them, and/or the failure to reasonably constrain them. Under these conditions, fit parameters are often correlated, and therefore lacking in statistical meaning. Here we introduce the uniqueness plot as a simple graphical tool for identifying bad peak fits in XPS, i.e., fit parameter correlation. These plots are widely used in spectroscopic ellipsometry. We illustrate uniqueness plots with two data sets: a C 1s narrow scan from ozone-treated carbon nanotube forests and an Si 2p narrow scan from an air-oxidized silicon wafer. For each fit, we consider different numbers of parameters and constraints on them. As expected, the uniqueness plots are parabolic when fewer fit parameters and/or more constraints are applied. However, they fan out and eventually become horizontal lines as more unconstrained parameters are included in the fits. Uniqueness plots are generated by plotting the chi squared (χ2) value for a fit vs. a systematically varied value of a parameter in the fit. The Abbe criterion is also considered as a figure of merit for uniqueness plots in the Supporting Information. We recommend that uniqueness plots be used by XPS practitioners for identifying inappropriate peak fits.

  1. X-ray Photoelectron Spectroscopy of Pyridinium-Based Ionic Liquids: Comparison to Imidazolium- and Pyrrolidinium-Based Analogues.

    Science.gov (United States)

    Men, Shuang; Mitchell, Daniel S; Lovelock, Kevin R J; Licence, Peter

    2015-07-20

    We investigate eight 1-alkylpyridinium-based ionic liquids of the form [Cn Py][A] by using X-ray photoelectron spectroscopy (XPS). The electronic environment of each element of the ionic liquids is analyzed. In particular, a reliable fitting model is developed for the C 1s region that applies to each of the ionic liquids. This model allows the accurate charge correction of binding energies and the determination of reliable and reproducible binding energies for each ionic liquid. Shake-up/off phenomena are determinedfor both C 1s and N 1s spectra. The electronic interaction between cations and anions is investigated for both simple ionic liquids and an example of an ionic-liquid mixture; the effect of the anion on the electronic environment of the cation is also explored. Throughout the study, a detailed comparison is made between [C8 Py][A] and analogues including 1-octyl-1-methylpyrrolidinium- ([C8 C1 Pyrr][A]), and 1-octyl-3-methylimidazolium- ([C8 C1 Im][A]) based samples, where X is common to all ionic liquids.

  2. X‐ray Photoelectron Spectroscopy of Pyridinium‐Based Ionic Liquids: Comparison to Imidazolium‐ and Pyrrolidinium‐Based Analogues

    Science.gov (United States)

    Mitchell, Daniel S.; Lovelock, Kevin R. J.

    2015-01-01

    Abstract We investigate eight 1‐alkylpyridinium‐based ionic liquids of the form [CnPy][A] by using X‐ray photoelectron spectroscopy (XPS). The electronic environment of each element of the ionic liquids is analyzed. In particular, a reliable fitting model is developed for the C 1s region that applies to each of the ionic liquids. This model allows the accurate charge correction of binding energies and the determination of reliable and reproducible binding energies for each ionic liquid. Shake‐up/off phenomena are determinedfor both C 1s and N 1s spectra. The electronic interaction between cations and anions is investigated for both simple ionic liquids and an example of an ionic‐liquid mixture; the effect of the anion on the electronic environment of the cation is also explored. Throughout the study, a detailed comparison is made between [C8Py][A] and analogues including 1‐octyl‐1‐methylpyrrolidinium‐ ([C8C1Pyrr][A]), and 1‐octyl‐3‐methylimidazolium‐ ([C8C1Im][A]) based samples, where X is common to all ionic liquids. PMID:25952131

  3. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy of Cobalt Perovskite Surfaces under Cathodic Polarization at High Temperatures

    KAUST Repository

    Crumlin, Ethan J.

    2013-08-08

    Heterostructured oxide interfaces have demonstrated enhanced oxygen reduction reaction rates at elevated temperatures (∼500-800 C); however, the physical origin underlying this enhancement is not well understood. By using synchrotron-based in situ ambient pressure X-ray photoelectron spectroscopy (APXPS), we focus on understanding the surface electronic structure, elemental composition, and chemical nature of epitaxial La0.8Sr 0.2CoO3-δ (LSC113), (La 0.5Sr0.5)2CoO4±δ (LSC214), and LSC214-decorated LSC113 (LSC 113/214) thin films as a function of applied electrical potentials (0 to -800 mV) at 520 C and p(O2) of 1 × 10-3 atm. Shifts in the top of the valence band binding energy and changes in the Sr 3d and O 1s spectral components under applied bias reveal key differences among the film chemistries, most notably in the degree of Sr segregation to the surface and quantity of active oxygen sites in the perovskite termination layer. These differences help to identify important factors governing the enhanced activity of oxygen electrocatalysis observed for the LSC113/214 heterostructured surface. © 2013 American Chemical Society.

  4. Interface investigations of a commercial lithium ion battery graphite anode material by sputter depth profile X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Niehoff, Philip; Passerini, Stefano; Winter, Martin

    2013-05-14

    Here we provide a detailed X-ray photoelectron spectroscopy (XPS) study of the electrode/electrolyte interface of a graphite anode from commercial NMC/graphite cells by intense sputter depth profiling using a polyatomic ion gun. The uniqueness of this method lies in the approach using 13-step sputter depth profiling (SDP) to obtain a detailed model of the film structure, which forms at the electrode/electrolyte interface often noted as the solid electrolyte interphase (SEI). In addition to the 13-step SDP, several reference experiments of the untreated anode before formation with and without electrolyte were carried out to support the interpretation. Within this work, it is shown that through charging effects during X-ray beam exposure chemical components cannot be determined by the binding energy (BE) values only, and in addition, that quantification by sputter rates is complicated for composite electrodes. A rough estimation of the SEI thickness was carried out by using the LiF and graphite signals as internal references.

  5. Excited state non-adiabatic dynamics of N-methylpyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Guorong [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Neville, Simon P. [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Schalk, Oliver [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 106 91 Stockholm (Sweden); Sekikawa, Taro [Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Ashfold, Michael N. R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Worth, Graham A. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Stolow, Albert, E-mail: astolow@uottawa.ca [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)

    2016-01-07

    The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A{sub 2}(πσ{sup ∗}) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B{sub 1}(π3p{sub y}) Rydberg state, followed by prompt internal conversion to the A{sub 2}(πσ{sup ∗}) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A{sub 2}(πσ{sup ∗}) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A{sub 2}(πσ{sup ∗}) state, facilitating wavepacket motion around the potential barrier in the N–CH{sub 3} dissociation coordinate.

  6. Characterization of photocatalytic TiO2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

    Science.gov (United States)

    Krishnan, Padmaja; Liu, Minghui; Itty, Pierre A.; Liu, Zhi; Rheinheimer, Vanessa; Zhang, Min-Hong; Monteiro, Paulo J. M.; Yu, Liya E.

    2017-01-01

    Consecutive eight study phases under the successive presence and absence of UV irradiation, water vapor, and oxygen were conducted to characterize surface changes in the photocatalytic TiO2 powder using near-ambient-pressure X-ray photoelectron spectroscopy (XPS). Both Ti 2p and O 1s spectra show hysteresis through the experimental course. Under all the study environments, the bridging hydroxyl (OHbr) and terminal hydroxyl (OHt) are identified at 1.1–1.3 eV and 2.1–2.3 eV above lattice oxygen, respectively. This enables novel and complementary approach to characterize reactivity of TiO2 powder. The dynamic behavior of surface-bound water molecules under each study environment is identified, while maintaining a constant distance of 1.3 eV from the position of water vapor. In the dark, the continual supply of both water vapor and oxygen is the key factor retaining the activated state of the TiO2 powder for a time period. Two new surface peaks at 1.7–1.8 and 4.0–4.2 eV above lattice oxygen are designated as peroxides (OOH/H2O2) and H2O2 dissolved in water, respectively. The persistent peroxides on the powder further explain previously observed prolonged oxidation capability of TiO2 powder without light irradiation. PMID:28240300

  7. Growth mechanisms and band bending in Cu and Pt on Ge(001) investigated by LEED and photoelectron spectroscopy

    Science.gov (United States)

    Tănase, Liviu Cristian; Bocîrnea, Amelia Elena; Şerban, Andreea Bianca; Abramiuc, Laura Elena; Bucur, Ioana Cristina; Lungu, George-Adrian; Costescu, Ruxandra Maria; Teodorescu, Cristian Mihail

    2016-11-01

    We investigate band bending effects occurring at the interface between atomically clean Ge(001) and molecular beam epitaxy (MBE) deposited copper and platinum. Low energy electron diffraction (LEED) confirmed the crystallinity of the surface, evidenced the formation of (2 × 1) and (1 × 2) reconstructions, and revealed that it is strongly affected with metal deposition. X-ray photoelectron spectroscopy (XPS) data let us assume a Stranski-Krastanov growth mechanism and confirmed that the observed band bending is associated to an ohmic contact in both cases. For the platinum contact, the high values of the apparent inelastic mean free path (IMFP) derived from the evolution of the XPS intensities indicate a prevalence of mixture of Pt with Ge nearby the interface. Pt deposited on Ge(001) does not behave like a Schottky contact, as one may have expected due to the higher work function of platinum. The observed effect is similar to the case where interfacial Pt had a lower work function by 2.25/1.96 eV than that of metallic Pt. We propose a model to explain this fact by the effective mass variation or to the conduction band broadening due to the strong intermixing of platinum with germanium under the surface.

  8. Reactivity of Au nanoparticles supported over SiO2 and TiO2 studiedby ambient pressure photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Herranz, Tirma; Deng, Xingyi; Cabot, Andreu; Alivisatos, Paul; Liu, Zhi; Soler-Illia, Galo; Salmeron, Miquel

    2009-04-15

    The influence of the metal cluster size and the identity of the support on the reactivity of gold based catalysts have been studied in the CO oxidation reaction. To overcome the structural complexity of the supported catalysts, gold nanoparticles synthesized from colloidal chemistry with precisely controlled size have been used. Those particles were supported over SiO{sub 2} and TiO{sub 2} and their catalytic activity was measured in a flow reactor. The reaction rate was dependent on the particle size and the support, suggesting two reaction pathways in the CO oxidation reaction. In parallel, ambient pressure photoelectron spectroscopy (APPS) has been performed under reaction conditions using bidimensional model catalysts prepared upon supporting the Au nanoparticles over planar polycrystalline SiO{sub 2} and TiO{sub 2} thin films by means of the Langmuir-Blodgett (LB) technique to mimic the characteristic of the powder samples. In this way, the catalytically active surface was characterized under true reaction conditions, revealing that during CO oxidation gold remains in the metallic state.

  9. General equation for size nanocharacterization of the core-shell nanoparticles by X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Gillet, Jean-Numa; Meunier, Michel

    2005-05-12

    Nanocharacterization is essential for nanoengineering of new types of core-shell (c-s) nanoparticles, which can be used to design new devices for photonics, electronics, catalysis, medicine, etc. X-ray photoelectron spectroscopy (XPS) has been widely used to study the elemental composition of the c-s nanoparticles. However, the physical and chemical properties of a c-s nanoparticle dramatically depend on the sizes of its core and shell. We therefore propose a general equation for the XPS intensity of a c-s nanoparticle, which is based on an analytical model. With this equation, XPS can now also be used for nanocharacterization of the core and shell sizes of the c-s nanoparticles (with a diameter smaller than or equal to the XPS probing depth of approximately 10 nm). To validate the new equation with experimental XPS data, we first determine the average shell thickness of a group of c-s nanoparticles by comparing the XPS intensity of reference bare cores to that of the c-s nanoparticles. Then we study the growth kinetics of the cores and shells of another group of c-s nanoparticles where the shells are obtained by oxidation.

  10. Oxidation and surface segregation of chromium in Fe–Cr alloys studied by Mössbauer and X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Idczak, R., E-mail: ridczak@ifd.uni.wroc.pl; Idczak, K.; Konieczny, R.

    2014-09-15

    The room temperature {sup 57}Fe Mössbauer and XPS spectra were measured for polycrystalline iron-based Fe–Cr alloys. The spectra were collected using three techniques: the transmission Mössbauer spectroscopy (TMS), the conversion electron Mössbauer spectroscopy (CEMS) and the X-ray photoelectron spectroscopy (XPS). The combination of these experimental techniques allows to determine changes in Cr concentration and the presence of oxygen in bulk, in the 300 nm pre-surface layer and on the surface of the studied alloys.

  11. Far-Infrared Spectroscopy of Cationic Polycyclic Aromatic Hydrocarbons: Zero Kinetic Energy Photoelectron Spectroscopy of Pentacene Vaporized from Laser Desorption

    CERN Document Server

    Zhang, J; Pei, L; Kong, W; Li, Aigen

    2012-01-01

    The distinctive set of infrared (IR) emission bands at 3.3, 6.2, 7.7, 8.6, and 11.3{\\mu}m are ubiquitously seen in a wide variety of astrophysical environments. They are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. However, not a single PAH species has yet been identified in space, as the mid-IR vibrational bands are mostly representative of functional groups and thus do not allow one to fingerprint individual PAH molecules. In contrast, the far-IR (FIR) bands are sensitive to the skeletal characteristics of a molecule, hence they are important for chemical identification of unknown species. With an aim to offer laboratory astrophysical data for the Herschel Space Observatory, Stratospheric Observatory for Infrared Astronomy, and similar future space missions, in this work we report neutral and cation FIR spectroscopy of pentacene (C_22H_14), a five-ring PAH molecule. We report three IR active modes of cationic pentacene at 53.3, 84.8, and 266{\\mu}m that may be detectable by space ...

  12. Probing Time-Dependent Molecular Dipoles on the Attosecond Time Scale

    Science.gov (United States)

    Neidel, Ch.; Klei, J.; Yang, C.-H.; Rouzée, A.; Vrakking, M. J. J.; Klünder, K.; Miranda, M.; Arnold, C. L.; Fordell, T.; L'Huillier, A.; Gisselbrecht, M.; Johnsson, P.; Dinh, M. P.; Suraud, E.; Reinhard, P.-G.; Despré, V.; Marques, M. A. L.; Lépine, F.

    2013-07-01

    Photoinduced molecular processes start with the interaction of the instantaneous electric field of the incident light with the electronic degrees of freedom. This early attosecond electronic motion impacts the fate of the photoinduced reactions. We report the first observation of attosecond time scale electron dynamics in a series of small- and medium-sized neutral molecules (N2, CO2, and C2H4), monitoring time-dependent variations of the parent molecular ion yield in the ionization by an attosecond pulse, and thereby probing the time-dependent dipole induced by a moderately strong near-infrared laser field. This approach can be generalized to other molecular species and may be regarded as a first example of molecular attosecond Stark spectroscopy.

  13. Attosecond physics at the nanoscale

    CERN Document Server

    Ciappina, M F; Landsman, A S; Okell, W; Zherebtsov, S; Förg, B; Schötz, J; Seiffert, J L; Fennel, T; Shaaran, T; Zimmermann, T; Chacón, A; Guichard, R; Zaïr, A; Tisch, J W G; Marangos, J P; Witting, T; Braun, A; Maier, S A; Roso, L; Krüger, M; Hommelhoff, P; Kling, M F; Krausz, F; Lewenstein, M

    2016-01-01

    Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds, which is comparable with the optical field. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this article we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spati...

  14. Attosecond double-slit experiment.

    Science.gov (United States)

    Lindner, F; Schätzel, M G; Walther, H; Baltuska, A; Goulielmakis, E; Krausz, F; Milosević, D B; Bauer, D; Becker, W; Paulus, G G

    2005-07-22

    A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (slits) of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are measured. A situation in which one and the same electron encounters a single and a double slit at the same time is observed. The investigation of the fringes makes possible interferometry on the attosecond time scale. From the number of visible fringes, for example, one derives that the slits are extended over about 500 as.

  15. Generation, temporal characterization and applications of femtosecond-/ attosecond extreme ultraviolet pulses

    Science.gov (United States)

    Thomann, Isabell

    The work of this thesis is arranged into three parts: (A) Generation and temporal characterization of extreme ultraviolet (EUV) attosecond pulses. In this work I present the generation and first temporal characterization of sub-optical cycle EUV radiation generated in a noble-gas filled hollow-core waveguide. Two regimes of EUV radiation were characterized, ranging from 200 attoseconds to ˜ 1 femtosecond in duration. The first regime that was characterized distinguishes itself from EUV radiation generated by other methods by its narrow (˜ 1 eV) spectral width, its simple energy tunability and its temporal confinement to ˜ 1 femtosecond. In the second regime, single isolated pulses of 200 attoseconds duration (and accordingly larger bandwidth) were generated. In both regimes dynamic phase-matching effects create an extremely short time window within which efficient nonlinear conversion is possible, while it is suppressed outside this window. Temporal characterization of the generated EUV pulses was approached by two-color pump-probe photoelectron spectroscopy. Therefore an efficient photoelectron spectrometer was set up, detecting electrons in a 2pi collection angle. For the interpretation of the experimental data, an analytical model as well as an iterative algorithm were developed, to allow extraction of complex EUV waveforms. The demonstrated radiation will allow for time-resolved studies of the fastest processes in molecules and condensed matter, while at the same time ensuring adequate energy resolution for addressing individual electronic states. (B) Application of a COLTRIMS reaction microscope in combination with femtosecond EUV pulses to questions in molecular physics. The combination of the sensitive detection capabilities of a COLTRIMS reaction microscope with the high time resolution of pump-probe experiments using femtosecond extreme-ultraviolet pulses makes it possible to answer very fundamental open questions in molecular physics such as the

  16. X-ray photoelectron spectroscopy study of pyrolytically coated graphite platforms submitted to simulated electrothermal atomic absorption spectrometry conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Frine [Laboratorio de Quimica Analitica, Centro de Quimica, Instituto Venezolano de Investigaciones Cientificas, IVIC, Apartado Postal 21827, Caracas 1020-A (Venezuela); Benzo, Zully [Laboratorio de Quimica Analitica, Centro de Quimica, Instituto Venezolano de Investigaciones Cientificas, IVIC, Apartado Postal 21827, Caracas 1020-A (Venezuela); Quintal, Manuelita [Laboratorio de Quimica Analitica, Centro de Quimica, Instituto Venezolano de Investigaciones Cientificas, IVIC, Apartado Postal 21827, Caracas 1020-A (Venezuela); Garaboto, Angel [Laboratorio de Quimica Analitica, Centro de Quimica, Instituto Venezolano de Investigaciones Cientificas, IVIC, Apartado Postal 21827, Caracas 1020-A (Venezuela); Albornoz, Alberto [Laboratorio de Fisicoquimica de Superficies, Centro de Quimica, Instituto Venezolano de Investigaciones Cientificas, IVIC, Apartado Postal 21827, Caracas 1020-A (Venezuela); Brito, Joaquin L. [Laboratorio de Fisicoquimica de Superficies, Centro de Quimica, Instituto Venezolano de Investigaciones Cientificas, IVIC, Apartado Postal 21827, Caracas 1020-A (Venezuela)]. E-mail: joabrito@ivic.ve

    2006-10-15

    The present work is part of an ongoing project aiming to a better understanding of the mechanisms of atomization on graphite furnace platforms used for electrothermal atomic absorption spectrometry (ETAAS). It reports the study of unused pyrolytic graphite coated platforms of commercial origin, as well as platforms thermally or thermo-chemically treated under simulated ETAAS analysis conditions. X-ray photoelectron spectroscopy (XPS) was employed to study the elements present at the surfaces of the platforms. New, unused platforms showed the presence of molybdenum, of unknown origin, in concentrations up to 1 at.%. Species in two different oxidations states (Mo{sup 6+} and Mo{sup 2+}) were detected by analyzing the Mo 3d spectral region with high resolution XPS. The analysis of the C 1s region demonstrated the presence of several signals, one of these at 283.3 eV related to the presence of Mo carbide. The O 1s region showed also various peaks, including a signal that can be attributed to the presence of MoO{sub 3}. Some carbon and oxygen signals were consistent with the presence of C=O and C-O- (probably C-OH) groups on the platforms surfaces. Upon thermal treatment up to 2900 deg. C, the intensity of the Mo signal decreased, but peaks due to Mo oxides (Mo{sup 6+} and Mo{sup 5+}) and carbide (Mo{sup 2+}) were still apparent. Thermo-chemical treatment with 3 vol.% HCl solutions and heating up to 2900 deg. C resulted in further diminution of the Mo signal, with complete disappearance of Mo carbide species. Depth profiling of unused platforms by Ar{sup +} ion etching at increasing time periods demonstrated that, upon removal of several layers of carbonaceous material, the Mo signal disappears suggesting that this contamination is present only at the surface of the pyrolytic graphite platform.

  17. X-ray photoelectron spectroscopy study of high-k CeO2/La2O3 stacked dielectrics

    Directory of Open Access Journals (Sweden)

    Jieqiong Zhang

    2014-11-01

    Full Text Available This work presents a detailed study on the chemical composition and bond structures of CeO2/La2O3 stacked gate dielectrics based on x-ray photoelectron spectroscopy (XPS measurements at different depths. The chemical bonding structures in the interfacial layers were revealed by Gaussian decompositions of Ce 3d, La 3d, Si 2s, and O 1s photoemission spectra at different depths. We found that La atoms can diffuse into the CeO2 layer and a cerium-lanthanum complex oxide was formed in between the CeO2 and La2O3 films. Ce3+ and Ce4+ states always coexist in the as-deposited CeO2 film. Quantitative analyses were also conducted. The amount of CeO2 phase decreases by about 8% as approaching the CeO2/La2O3 interface. In addition, as compared with the single layer La2O3 sample, the CeO2/La2O3 stack exhibits a larger extent of silicon oxidation at the La2O3/Si interface. For the CeO2/La2O3 gate stack, the out-diffused lanthanum atoms can promote the reduction of CeO2 which produce more atomic oxygen. This result confirms the significant improvement of electrical properties of CeO2/La2O3 gated devices as the excess oxygen would help to reduce the oxygen vacancies in the film and would suppress the formation of interfacial La-silicide also.

  18. Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, S., E-mail: suhaimihas@uthm.edu.my; Yusof, M. S., E-mail: mdsalleh@uthm.edu.my; Maksud, M. I., E-mail: midris1973@gmail.com [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor (Malaysia); Embong, Z., E-mail: zaidi@uthm.edu.my [Faculty of Science, Technology and Human Development, Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor (Malaysia)

    2016-01-22

    Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La{sub 2}O{sub 3}) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La{sub 2}O{sub 3} deposited on the surface of Si wafer substrate was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La{sub 2}O{sub 3} and La(OH){sub 3}. The information of oxygen species, O{sup 2-} component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O{sup 2−}), two chemisorb component (La{sub 2}O{sub 3}) and La(OH){sub 3} and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later.

  19. Uniqueness plots: A simple graphical tool for identifying poor peak fits in X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Bhupinder; Diwan, Anubhav; Jain, Varun [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84606 (United States); Herrera-Gomez, Alberto [CINVESTAV-Unidad Queretaro, Queretaro, 76230 (Mexico); Terry, Jeff [Department of Physics, Illinois Institute of Technology, Chicago, IL, 60616 (United States); Linford, Matthew R., E-mail: mrlinford@chem.byu.edu [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84606 (United States)

    2016-11-30

    Highlights: • Uniqueness plots are introduced as a new tool for identifying poor XPS peak fits. • Uniqueness plots are demonstrated on real XPS data sets. • A horizontal line in a uniqueness plot indicates a poor fit, i.e., fit parameter correlation. • A parabolic shape in a uniqueness plot indicates that a fit may be appropriate. - Abstract: Peak fitting is an essential part of X-ray photoelectron spectroscopy (XPS) narrow scan analysis, and the Literature contains both good and bad examples of peak fitting. A common cause of poor peak fitting is the inclusion of too many fit parameters, often without a sound chemical and/or physical basis for them, and/or the failure to reasonably constrain them. Under these conditions, fit parameters are often correlated, and therefore lacking in statistical meaning. Here we introduce the uniqueness plot as a simple graphical tool for identifying bad peak fits in XPS, i.e., fit parameter correlation. These plots are widely used in spectroscopic ellipsometry. We illustrate uniqueness plots with two data sets: a C 1s narrow scan from ozone-treated carbon nanotube forests and an Si 2p narrow scan from an air-oxidized silicon wafer. For each fit, we consider different numbers of parameters and constraints on them. As expected, the uniqueness plots are parabolic when fewer fit parameters and/or more constraints are applied. However, they fan out and eventually become horizontal lines as more unconstrained parameters are included in the fits. Uniqueness plots are generated by plotting the chi squared (χ{sup 2}) value for a fit vs. a systematically varied value of a parameter in the fit. The Abbe criterion is also considered as a figure of merit for uniqueness plots in the Supporting Information. We recommend that uniqueness plots be used by XPS practitioners for identifying inappropriate peak fits.

  20. Band offset in zinc oxy-sulfide/cubic-tin sulfide interface from X-ray photoelectron spectroscopy

    Science.gov (United States)

    K. C., Sanal; Nair, P. K.; Nair, M. T. S.

    2017-02-01

    Zinc oxy-sulfide, ZnOxS1-x, has been found to provide better band alignment in thin film solar cells of tin sulfide of orthorhombic crystalline structure. Here we examine ZnOxS1-x/SnS-CUB interface, in which the ZnOxS1-x thin film was deposited by radio frequency (rf) magnetron sputtering on SnS thin film of cubic (CUB) crystalline structure with a band gap (Eg) of 1.72 eV, obtained via chemical deposition. X-ray photoelectron spectroscopy provides the valence band maxima of the materials and hence places the conduction band offset of 0.41 eV for SnS-CUB/ZnO0.27S0.73 and -0.28 eV for SnS-CUB/ZnO0.88S0.12 interfaces. Thin films of ZnOxS1-x with 175-240 nm in thickness were deposited from targets prepared with different ZnO to ZnS molar ratios. With the target of molar ratio of 1:13.4, the thin films are of composition ZnO0.27S0.73 with hexagonal crystalline structure and with that of 1:1.7 ratio, it is ZnO0.88S0.12. The optical band gap of the ZnOxS1-x thin films varies from 2.90 eV to 3.21 eV as the sulfur to zinc ratio in the film increases from 0.12:1 to 0.73:1 as determined from X-ray diffraction patterns. Thus, band offsets sought for absorber materials and zinc oxy-sulfide in solar cells may be achieved through a choice of ZnO:ZnS ratio in the sputtering target.

  1. X-ray Photoelectron Spectroscopy Study of Indium Tin Oxide Films Deposited at Various Oxygen Partial Pressures

    Science.gov (United States)

    Peng, Shou; Cao, Xin; Pan, Jingong; Wang, Xinwei; Tan, Xuehai; Delahoy, Alan E.; Chin, Ken K.

    2017-02-01

    Here, a systematic experimental study on indium tin oxide (ITO) films is presented to investigate the effects of oxygen partial pressure on the film's electrical properties. The results of Hall measurements show that adding more oxygen in the sputtering gas has negative influences on the electrical conductivity of ITO films. As O2/(O2 + Ar)% in the sputtering gas is increased from 0 to 6.98%, the resistivity of ITO film rises almost exponentially from 7.9 × 10-4 to 4.1 × 10-2 Ω cm, with the carrier density decreasing from 4.8 × 1020 to 5.4 × 1018 cm-3. The origins of these negative effects are discussed with focuses on the concentration of ionized impurities and the scattering of grain barriers. Extensive x-ray photoelectron spectroscopy (XPS) analyses were employed to gain insight into the concentration of ionized impurities, demonstrating a strong correlation between the oxygen vacancy concentration and the carrier density in ITO films as a function of sputtering O2 partial pressure. Other microstructural characterization techniques including x-ray diffraction (XRD), high-magnification scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) analyses were used to evaluate the average grain size of ITO films. For ITO films that have carrier density above 1019 cm-3, scattering on grain boundaries and other crystallographic defects show negligible effects on the carrier transport. The results point to the oxygen vacancy concentration that dictates the carrier density and, thus, the resistivity of magnetron-sputtered ITO films.

  2. Quantitative X-ray photoelectron spectroscopy-based depth profiling of bioleached arsenopyrite surface by Acidithiobacillus ferrooxidans

    Science.gov (United States)

    Zhu, Tingting; Lu, Xiancai; Liu, Huan; Li, Juan; Zhu, Xiangyu; Lu, Jianjun; Wang, Rucheng

    2014-02-01

    In supergene environments, microbial activities significantly enhance sulfide oxidation and result in the release of heavy metals, causing serious contamination of soils and waters. As the most commonly encountered arsenic mineral in nature, arsenopyrite (FeAsS) accounts for arsenic contaminants in various environments. In order to investigate the geochemical behavior of arsenic during microbial oxidation of arsenopyrite, (2 3 0) surfaces of arsenopyrite slices were characterized after acidic (pH 2.00) and oxidative decomposition with or without an acidophilic microorganism Acidithiobacillus ferrooxidans. The morphology as well as chemical and elemental depth profiles of the oxidized arsenopyrite surface were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. With the mediation of bacteria, cell-shaped and acicular pits were observed on the reacted arsenopyrite surface, and the concentration of released arsenic species in solution was 50 times as high as that of the abiotic reaction after 10 days reaction. Fine-scale XPS depth profiles of the reacted arsenopyrite surfaces after both microbial and abiotic oxidation provided insights into the changes in chemical states of the elements in arsenopyrite surface layers. Within the 450 nm surface layer of abiotically oxidized arsenopyrite, Fe(III)-oxides appeared and gradually increased towards the surface, and detectable sulfite and monovalent arsenic appeared above 50 nm. In comparison, higher contents of ferric sulfate, sulfite, and arsenite were found in the surface layer of approximately 3 μm of the microbially oxidized arsenopyrite. Intermediates, such as Fe(III)-AsS and S0, were detectable in the presence of bacteria. Changes of oxidative species derived from XPS depth profiles show the oxidation sequence is Fe > As = S in abiotic oxidation, and Fe > S > As in microbial oxidation. Based on these results, a possible reaction path of microbial oxidation was proposed in a concept model.

  3. Determination of 4f energy levels for trivalent lanthanide ions in YAlO{sub 3} by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Yuhei; Ueda, Kazushige, E-mail: kueda@che.kyutech.ac.jp

    2016-09-01

    A simple method to analyze 4f energy levels of trivalent lanthanide (Ln) ions was demonstrated by conventional X-ray photoelectron spectroscopy (XPS) measurements using Ln ions doped YAlO{sub 3} sintered polycrystalline samples. Although XPS peaks derived from Ln 4f states overlapped with the host's valence band consisting of O 2p states, the difference XPS spectra between Ln doped and non-doped samples showed only the Ln 4f peaks due to the large difference of photoionization cross sections between Ln 4f and O 2p orbitals. The difference spectra showing Ln 4f states were aligned at the valence band maximum (VBM) making use of the peaks of Al 2p inner shells, and the Ln{sup 3+} 4f energy levels referred to the VBM were determined from the Ln{sup 3+} 4f peak energies. The Ln{sup 3+} 4f energy levels obtained by this simple method were in good agreement with those previously obtained by resonant ultraviolet photoelectron spectroscopy measurements using single crystal samples. - Highlights: • Lanthanide (Ln) 4f energy in YAlO{sub 3} was studied by X-ray photoelectron spectroscopy. • The method used differences in photoionization probability between Ln 4f and O 2p. • Ln 4f states were obtained by difference spectra between Ln- and non-doped samples. • Obtained 4f energy levels agreed with those reported by a sophisticated method.

  4. A high pressure x-ray photoelectron spectroscopy experimental method for characterization of solid-liquid interfaces demonstrated with a Li-ion battery system

    Energy Technology Data Exchange (ETDEWEB)

    Maibach, Julia; Xu, Chao; Gustafsson, Torbjörn; Edström, Kristina [Department of Chemistry–Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala (Sweden); Eriksson, Susanna K. [Department of Chemistry–Ångström Laboratory, Uppsala University, Box 523, SE-751 20 Uppsala (Sweden); Åhlund, John [VG Scienta AB, Box 15120, SE-750 15 Uppsala (Sweden); Siegbahn, Hans; Rensmo, Håkan; Hahlin, Maria, E-mail: maria.hahlin@physics.uu.se [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden)

    2015-04-15

    We report a methodology for a direct investigation of the solid/liquid interface using high pressure x-ray photoelectron spectroscopy (HPXPS). The technique was demonstrated with an electrochemical system represented by a Li-ion battery using a silicon electrode and a liquid electrolyte of LiClO{sub 4} in propylene carbonate (PC) cycled versus metallic lithium. For the first time the presence of a liquid electrolyte was realized using a transfer procedure where the sample was introduced into a 2 mbar N{sub 2} environment in the analysis chamber without an intermediate ultrahigh vacuum (UHV) step in the load lock. The procedure was characterized in detail concerning lateral drop gradients as well as stability of measurement conditions over time. The X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the solid substrate and the liquid electrolyte can be observed simultaneously. The results show that the solid electrolyte interphase (SEI) composition for the wet electrode is stable within the probing time and generally agrees well with traditional UHV studies. Since the methodology can easily be adjusted to various high pressure photoelectron spectroscopy systems, extending the approach towards operando solid/liquid interface studies using liquid electrolytes seems now feasible.

  5. Ptychographic reconstruction of attosecond pulses

    CERN Document Server

    Lucchini, M; Ludwig, A; Gallmann, L; Keller, U; Feurer, T

    2015-01-01

    We demonstrate a new attosecond pulse reconstruction modality which uses an algorithm that is derived from ptychography. In contrast to other methods, energy and delay sampling are not correlated, and as a result, the number of electron spectra to record is considerably smaller. Together with the robust algorithm, this leads to a more precise and fast convergence of the reconstruction.

  6. Thermal decomposition of methyl 2-azidopropionate studied by UV photoelectron spectroscopy and matrix isolation IR spectroscopy: heterocyclic intermediate vs imine formation.

    Science.gov (United States)

    Pinto, R M; Dias, A A; Costa, M L; Rodrigues, P; Barros, M T; Ogden, J S; Dyke, J M

    2011-08-01

    Methyl 2-azidopropionate (N(3)CH(3)CHCOOCH(3), M2AP) has been synthesized and characterized by different spectroscopic methods, and the thermal decomposition of this molecule has been investigated by matrix isolation infrared (IR) spectroscopy and ultraviolet photoelectron spectroscopy (UVPES). Computational methods have been employed in the spectral simulation of both UVPES and matrix IR spectra and in the rationalization of the thermal decomposition results. M2AP presents a HOMO vertical ionization energy (VIE) of 9.60 ± 0.03 eV and contributions from all four lowest-energy conformations of this molecule are detected in the gas phase. Its thermal decomposition starts at ca. 400 °C and is complete at ca. 650 °C, yielding N(2), CO, CO(2), CH(3)CN, and CH(3)OH as the final decomposition products. Methyl formate (MF) and CH(4) are also found during the pyrolysis process. Analysis of the potential energy surface of the decomposition of M2AP indicates that M2AP decomposes preferentially into the corresponding imine (M2IP), through a 1,2-H shift synchronous with the N(2) elimination (Type 1 mechanism), requiring an activation energy of 160.8 kJ/mol. The imine further decomposes via two competitive routes: one accounting for CO, CH(3)OH, and CH(3)CN (ΔE(G3) = 260.2 kJ/mol) and another leading to CO(2), CH(4), and CH(3)CN (ΔE(G3) = 268.6 kJ/mol). A heterocyclic intermediate (Type 2 mechanism)-4-Me-5-oxazolidone-can also be formed from M2AP via H transfer from the remote O-CH(3) group, together with the N(2) elimination (ΔE(G3) = 260.2 kJ/mol). Finally, a third pathway which accounts for the formation of MF through an M2AP isomer is envisioned.

  7. Attosecond VUV Coherent Control of Molecular Dynamics

    CERN Document Server

    Ranitovic, P; Riviere, P; Palacios, A; Tong, X M; Toshima, N; Gonzalez-Castrillo, A; Martin, L; Martin, F; Murnane, M M; Kapteyn, H C

    2014-01-01

    High harmonic light sources make it possible to access attosecond time-scales, thus opening up the prospect of manipulating electronic wave packets for steering molecular dynamics. However, two decades after the birth of attosecond physics, the concept of attosecond chemistry has not yet been realized. This is because excitation and manipulation of molecular orbitals requires precisely controlled attosecond waveforms in the deep ultraviolet, which have not yet been synthesized. Here, we present a novel approach using attosecond vacuum ultraviolet pulse-trains to coherently excite and control the outcome of a simple chemical reaction in a deuterium molecule in a non-Born Oppenheimer regime. By controlling the interfering pathways of electron wave packets in the excited neutral and singly-ionized molecule, we unambiguously show that we can switch the excited electronic state on attosecond timescales, coherently guide the nuclear wave packets to dictate the way a neutral molecule vibrates, and steer and manipula...

  8. Efficient generation of isolated attosecond pulses with high beam-quality by two-color Bessel-Gauss beams

    CERN Document Server

    Wang, Zhe; Zhang, Qingbin; Wang, Shaoyi; Lu, Peixiang

    2011-01-01

    The generation of isolated attosecond pulses with high efficiency and high beam quality is essential for attosec- ond spectroscopy. We numerically investigate the supercontinuum generation in a neutral rare-gas medium driven by a two-color Bessel-Gauss beam. The results show that an efficient smooth supercontinuum in the plateau is obtained after propagation, and the spatial profile of the generated attosecond pulse is Gaussian-like with the divergence angle of 0.1 degree in the far field. This bright source with high beam quality is beneficial for detecting and controlling the microscopic processes on attosecond time scale.

  9. Application of high-resolution photoelectron spectroscopy: Vibrational resolved C 1s and O 1s spectra of CO adsorbed on Ni(100)

    Energy Technology Data Exchange (ETDEWEB)

    Foehlisch, A.; Nilsson, A.; Martensson, N. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    There are various effects which determine the line shape of a core-level electron spectrum. These are due to the finite life-time of the core hole, inelastic scattering of the outgoing photoelectron, electronic shake-up and shake-off processes and vibrational excitations. For free atoms and molecules the different contributions to the observed line shapes can often be well separated. For solids, surfaces and adsorbates the line shapes are in general much broader and it has in the past been assumed that no separation of the various contributions can be made. In the present report the authors will show that this is indeed not the case. Surprisingly, the vibrational fine structure of CO adsorbed on Ni(100) can be resolved in the C 1s and O 1s electron spectra. This was achieved by the combination of highly monochromatized soft X-rays from B18.0 with a high resolution Scienta 200 mm photoelectron spectrometer. X-ray photoelectron spectroscopy (XPS) with tunable excitation energy yields as a core level spectroscopy atomic and site-specific information. The presented measurements allow for a determination of internuclear distances and potential energy curves in corehole ionized adsorbed molecules. The authors analysis of the c(2x2) phase CO/Ni(100) on {open_quotes}top{close_quotes} yielded a vibrational splitting of 217 +/- 2 meV for C 1s ionization. For O 1s ionization a splitting of 173 +/- 8 meV was found.

  10. Properties of iron sulfide, hydrosulfide, and mixed sulfide/hydrosulfide cluster anions through photoelectron spectroscopy and density functional theory calculations

    Science.gov (United States)

    Yin, Shi; Bernstein, Elliot R.

    2016-10-01

    A new magnetic-bottle time-of-flight photoelectron spectroscopy (PES) apparatus is constructed in our laboratory. The PES spectra of iron sulfide, hydrosulfide, and mixed sulfide/hydrosulfide [FeSm(SH)n-; m, n = 0-3, 0 theory. The most probable structures and ground state spin multiplicity for these cluster anions are tentatively assigned by comparing their theoretical first vertical detachment energies (VDEs) with their respective experiment values. The behavior of S and (SH) as ligands in these iron sulfide, hydrosulfide, and mixed sulfide/hydrosulfide cluster anions is investigated and compared. The experimental first VDEs for Fe(SH)1-3- cluster anions are lower than those found for their respective FeS1-3- cluster anions. The experimental first VDEs for FeS1-3- clusters are observed to increase for the first two S atoms bound to Fe-; however, due to the formation of an S-S bond for the FeS3- cluster, its first VDE is found to be ˜0.41 eV lower than the first VDE for the FeS2- cluster. The first VDEs of Fe(SH)1-3- cluster anions are observed to increase with the increasing numbers of SH groups. The calculated partial charges of the Fe atom for ground state FeS1-3- and Fe(SH)1-3- clusters are apparently related to and correlated with their determined first VDEs. The higher first VDE is correlated with a higher, more positive partial charge for the Fe atom of these cluster anions. Iron sulfide/hydrosulfide mixed cluster anions are also explored in this work: the first VDE for FeS(SH)- is lower than that for FeS2-, but higher than that for Fe(SH)2-; the first VDEs for FeS2(SH)- and FeS(SH)2- are close to that for FeS3-, but higher than that for Fe(SH)3-. The first VDEs of general iron sulfide, hydrosulfide, and mixed sulfide/hydrosulfide clusters [FeSm(SH)n-; m, n = 0-3, 0 < (m + n) ≤ 3] are dependent on three properties of these anions: 1. the partial charge on the Fe atom, 2. disulfide bond formation (S-S) in the cluster, and 3. the number of hydrosulfide

  11. Flexible Acyclic Polyol-Chloride Anion Complexes and Their Characterization by Photoelectron Spectroscopy and Variable Temperature Binding Constant Determinations

    Energy Technology Data Exchange (ETDEWEB)

    Shokri, Alireza; Wang, Xue B.; Wang, Yangping; O' Doherty, George A.; Kass, Steven R.

    2016-03-17

    Flexible acyclic alcohols with 1–5 hydroxyl groups were bound to chloride anion and these complexes were interrogated by negative ion photoelectron spectroscopy and companion density functional theory computations. The resulting vertical detachment energies are reproduced on average to 0.10 eV by M06-2X/aug-cc-pVTZ predictions and range from 4.45 – 5.96 eV. These values are 0.84 – 2.35 eV larger than the adiabatic detachment energy of Cl– as a result of the larger hydrogen bond networks in the bigger polyols. Adiabatic detachment energies of the alcohol–Cl– clusters are more difficult to determine both experimentally and computationally. This is due to the large geometry changes that occur upon photodetachment and the large bond dissociation energy of H–Cl which enables the resulting chlorine atom to abstract a hydrogen from any of the methylene (CH2) or methine (CH) positions. Both ionic and non-ionic hydrogen bonds (i.e., OH•••Cl– and OH•••OH•••Cl–) form in the larger polyols complexes, and are found to be energetically comparable. Subtle structural differences, consequently can lead to the formation of different types of hydrogen bonds and maximizing the ionic ones is not always preferred. Solution equilibrium binding constants between the alcohols and tetrrabuylammonium chloride (TBACl) in acetonitrile at -24.2, 22.0, and 53.6 °C were also determined. The free energies of association are nearly identical for all of the substrates (i.e., ΔG° = -2.8 ± 0.7 kcal mol–1). Compensating enthalpy and entropy values reveal, contrary to expectation and the intrinsic gas-phase preferences, that the bigger systems with more hydroxyl groups are entropically favored and enthalpically disfavored relative to the smaller species. This suggests that more solvent molecules are released upon binding TBACl to alcohols with more hydroxyl groups and is consistent with the measured negative heat capacities. These quantities increase with

  12. Al capping layers for nondestructive x-ray photoelectron spectroscopy analyses of transition-metal nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Greczynski, Grzegorz, E-mail: grzgr@ifm.liu.se; Hultman, Lars [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden); Petrov, Ivan [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping, Sweden and Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States); Greene, J. E. [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden); Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801(United States); Department of Physics, University of Illinois, Urbana, Illinois 61801 (United States)

    2015-09-15

    X-ray photoelectron spectroscopy (XPS) compositional analyses of materials that have been air exposed typically require ion etching in order to remove contaminated surface layers. However, the etching step can lead to changes in sample surface and near-surface compositions due to preferential elemental sputter ejection and forward recoil implantation; this is a particular problem for metal/gas compounds and alloys such as nitrides and oxides. Here, the authors use TiN as a model system and compare XPS analysis results from three sets of polycrystalline TiN/Si(001) films deposited by reactive magnetron sputtering in a separate vacuum chamber. The films are either (1) air-exposed for ≤10 min prior to insertion into the ultrahigh-vacuum (UHV) XPS system; (2) air-exposed and subject to ion etching, using different ion energies and beam incidence angles, in the XPS chamber prior to analysis; or (3) Al-capped in-situ in the deposition system prior to air-exposure and loading into the XPS instrument. The authors show that thin, 1.5–6.0 nm, Al capping layers provide effective barriers to oxidation and contamination of TiN surfaces, thus allowing nondestructive acquisition of high-resolution core-level spectra representative of clean samples, and, hence, correct bonding assignments. The Ti 2p and N 1s satellite features, which are sensitive to ion bombardment, exhibit high intensities comparable to those obtained from single-crystal TiN/MgO(001) films grown and analyzed in-situ in a UHV XPS system and there is no indication of Al/TiN interfacial reactions. XPS-determined N/Ti concentrations acquired from Al/TiN samples agree very well with Rutherford backscattering and elastic recoil analysis results while ion-etched air-exposed samples exhibit strong N loss due to preferential resputtering. The intensities and shapes of the Ti 2p and N 1s core level signals from Al/TiN/Si(001) samples do not change following long-term (up to 70 days) exposure to ambient conditions

  13. Probing the structures and chemical bonding of boron-boronyl clusters using photoelectron spectroscopy and computational chemistry: B4(BO)(n)- (n = 1-3).

    Science.gov (United States)

    Chen, Qiang; Zhai, Hua-Jin; Li, Si-Dian; Wang, Lai-Sheng

    2012-07-28

    The electronic and structural properties of a series of boron oxide clusters, B(5)O(-), B(6)O(2)(-), and B(7)O(3)(-), are studied using photoelectron spectroscopy and density functional calculations. Vibrationally resolved photoelectron spectra are obtained, yielding electron affinities of 3.45, 3.54, and 4.94 eV for the corresponding neutrals, B(5)O, B(6)O(2), and B(7)O(3), respectively. Structural optimizations show that these oxide clusters can be formulated as B(4)(BO)(n)(-) (n = 1-3), which involve boronyls coordinated to a planar rhombic B(4) cluster. Chemical bonding analyses indicate that the B(4)(BO)(n)(-) clusters are all aromatic species with two π electrons.

  14. Probing the structures and chemical bonding of boron-boronyl clusters using photoelectron spectroscopy and computational chemistry: B4(BO)n- (n = 1-3)

    Science.gov (United States)

    Chen, Qiang; Zhai, Hua-Jin; Li, Si-Dian; Wang, Lai-Sheng

    2012-07-01

    The electronic and structural properties of a series of boron oxide clusters, B5O-, B6O2-, and B7O3-, are studied using photoelectron spectroscopy and density functional calculations. Vibrationally resolved photoelectron spectra are obtained, yielding electron affinities of 3.45, 3.54, and 4.94 eV for the corresponding neutrals, B5O, B6O2, and B7O3, respectively. Structural optimizations show that these oxide clusters can be formulated as B4(BO)n- (n = 1-3), which involve boronyls coordinated to a planar rhombic B4 cluster. Chemical bonding analyses indicate that the B4(BO)n- clusters are all aromatic species with two π electrons.

  15. Photoelectron spectroscopy of aqueous solutions: streaming potentials of NaX (X = Cl, Br, and I) solutions and electron binding energies of liquid water and X-.

    Science.gov (United States)

    Kurahashi, Naoya; Karashima, Shutaro; Tang, Ying; Horio, Takuya; Abulimiti, Bumaliya; Suzuki, Yoshi-Ichi; Ogi, Yoshihiro; Oura, Masaki; Suzuki, Toshinori

    2014-05-07

    The streaming potentials of liquid beams of aqueous NaCl, NaBr, and NaI solutions are measured using soft X-ray, He(I), and laser multiphoton ionization photoelectron spectroscopy. Gaseous molecules are ionized in the vicinity of liquid beams and the photoelectron energy shifts are measured as a function of the distance between the ionization point and the liquid beam. The streaming potentials change their polarity with concentration of electrolytes, from which the singular points of concentration eliminating the streaming potentials are determined. The streaming currents measured in air also vanish at these concentrations. The electron binding energies of liquid water and I(-), Br(-), and Cl(-) anions are revisited and determined more accurately than in previous studies.

  16. Attosecond Interference Induced by Coulomb-Field-Driven Transverse Backward-Scattering Electron Wave-Packets

    CERN Document Server

    Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Yu, Xianhuan; Yang, Weifeng; Hu, Shilin; Chen, Jing; Xu, SongPo; Chen, YongJu; Quan, Wei; Liu, XiaoJun

    2016-01-01

    A novel and universal interference structure is found in the photoelectron momentum distribution of atoms in intense infrared laser field. Theoretical analysis shows that this structure can be attributed to a new form of Coulomb-field-driven backward-scattering of photoelectrons in the direction perpendicular to the laser field, in contrast to the conventional rescattering along the laser polarization direction. This transverse backward-scattering process is closely related to a family of photoelectrons initially ionized within a time interval of less than 200 attosecond around the crest of the laser electric field. Those electrons, acquiring near-zero return energy in the laser field, will be pulled back solely by the ionic Coulomb field and backscattered in the transverse direction. Moreover, this rescattering process mainly occurs at the first or the second return times, giving rise to different phases of the photoelectrons. The interference between these photoelectrons leads to unique curved interference ...

  17. Attosecond Physics at the nanoscale.

    Science.gov (United States)

    Ciappina, Marcelo F; Perez-Hernandez, J; Landsman, Alexandra; Okell, William; Zherebtsov, Sergey; Förg, Benjamin; Schötz, Johannes; Seiffert, Lennart; Fennel, Thomas; Shaaran, Tahir; Zimmermann, Tomas; Chacón, Alexis; Guichard, Roland; Zair, Amelle; Tisch, John; Marangos, J; Witting, Tobias; Braun, Avi; Maier, Stefan; Roso, Luis; Krüger, Michael; Hommelhoff, Peter; Kling, Matthias; Krausz, Ferenc; Lewenstein, Maciej

    2017-01-06

    Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds, which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is 152 as. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this report on progress we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metal- lic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as above-threshold ionization and high-order harmonic generation. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nano physics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the induced fields and the unique electron dynamics initiated

  18. Electron-hole recombination on ZnO(0001) single-crystal surface studied by time-resolved soft X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yukawa, R.; Yamamoto, S.; Ogawa, M.; Yamamoto, Sh.; Fujikawa, K.; Hobara, R.; Matsuda, I., E-mail: imatsuda@issp.u-tokyo.ac.jp [Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Ozawa, K. [Department of Chemistry and Materials Science, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan); Emori, M.; Sakama, H. [Department of Physics, Sophia University, Chiyoda-ku, Tokyo 102-8554 (Japan); Kitagawa, S.; Daimon, H. [Nara Institute of Science and Technology (NAIST), Ikoma, Nara 630-0192 (Japan)

    2014-10-13

    Time-resolved soft X-ray photoelectron spectroscopy (PES) experiments were performed with time scales from picoseconds to nanoseconds to trace relaxation of surface photovoltage on the ZnO(0001) single crystal surface in real time. The band diagram of the surface has been obtained numerically using PES data, showing a depletion layer which extends to 1 μm. Temporal evolution of the photovoltage effect is well explained by a recombination process of a thermionic model, giving the photoexcited carrier lifetime of about 1 ps at the surface under the flat band condition. This lifetime agrees with a temporal range reported by the previous time-resolved optical experiments.

  19. Complementary low energy ion scattering and X-ray photoelectron spectroscopy characterization of polystyrene submitted to N{sub 2}/H{sub 2} glow discharge

    Energy Technology Data Exchange (ETDEWEB)

    Bonatto, F., E-mail: bonatto02@yahoo.com.br [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 91509-900 (Brazil); Rovani, S. [Universidade de Caxias do Sul, Caxias do Sul, Rio Grande do Sul 95070-560 (Brazil); Kaufmann, I.R.; Soares, G.V. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 91509-900 (Brazil); Baumvol, I.J.R. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 91509-900 (Brazil); Universidade de Caxias do Sul, Caxias do Sul, Rio Grande do Sul 95070-560 (Brazil); Krug, C. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 91509-900 (Brazil)

    2012-02-15

    Low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) were used to access the elemental composition and chemical bonding characteristics of polystyrene (PS) surfaces sequentially treated by corona and glow discharge (plasma) processing in N{sub 2}/H{sub 2} ambient. The latter has shown activity as suppressor of pathogenic Staphylococcus epidermidis biofilms. LEIS indicated that oxygen from the corona discharge process is progressively replaced by nitrogen at the PS surface. XPS shows C=N and N-C=O chemical groups as significant inhibitors of bacterial adhesion, suggesting application in medical devices.

  20. Effects of Varied Cleaning Methods on Ni-5% W Substrate for Dip-Coating of Water-based Buffer Layers: An X-ray Photoelectron Spectroscopy Study

    Directory of Open Access Journals (Sweden)

    Isabel Van Driessche

    2012-08-01

    Full Text Available This work describes various combinations of cleaning methods involved in the preparation of Ni-5% W substrates for the deposition of buffer layers using water-based solvents. The substrate has been studied for its surface properties using X-ray photoelectron spectroscopy (XPS. The contaminants in the substrates have been quantified and the appropriate cleaning method was chosen in terms of contaminants level and showing good surface crystallinity to further consider them for depositing chemical solution-based buffer layers for Y1Ba2Cu3Oy (YBCO coated conductors.

  1. X-ray photoelectron spectroscopy analysis for undegraded and degraded Gd2O2S:Tb3+ phosphor thin films

    Science.gov (United States)

    Dolo, J. J.; Swart, H. C.; Terblans, J. J.; Coetsee, E.; Ntwaeaborwa, O. M.; Dejene, B. F.

    2012-05-01

    This paper presents the X-ray Photoelectron Spectroscopy (XPS) analysis for the undegraded and degraded Gd2O2S:Tb3+ thin film phosphor. The thin films were grown with the pulsed laser deposition (PLD) technique. XPS measurements were done on Gd2O2S:Tb3+ phosphor thin films before and after electron degradation. The XPS technique has proven the presence of Gd2O3 on the degraded and undegraded thin film spots. The presence of the SO2 bonding was also detected after degradation. This clearly indicates that surface reactions did occur during prolonged electron bombardment in an oxygen atmosphere.

  2. Investigation of Oxygen Vacancy and Interstitial Oxygen Defects in ZnO Films by Photoluminescence and X-Ray Photoelectron Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    FAN Hai-Bo; YANG Shao-Yan; ZHANG Pan-Feng; WEI Hong-Yuan; LIU Xiang-Lin; JIAO Chun-Mei; ZHU Qin-Sheng; CHEN Yong-Hai; WANG Zhan-Guo

    2007-01-01

    ZnO films prepared at different temperatures and annealed at 900 C in oxygen are studied by photoluminescence (PL) and x-ray photoelectron spectroscopy (XPS). It is observed that in the PL of the as-grown films the green luminescence (GL) and the yellow luminescence (YL) are related, and after annealing the GL is restrained and the YL is enhanced. The O 1s XPS results also show the coexistence of oxygen vacancy (Vo) and interstitial oxygen (Oi) before annealing and the quenching of the Vo after annealing. By combining the two results it is deduced that the GL and YL are related to the Vo and Oi defects, respectively.

  3. X-ray photoelectron spectroscopy studies of Ag-doped thin amorphous Ge{sub x}Sb{sub 40-x}S{sub 60} films

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, R.K.; Fitzgerald, A.G.; Christova, K

    2002-12-30

    X-ray photoelectron spectroscopy has been used to determine the binding energies of the core electrons in Ag-doped amorphous thin Ge{sub x}Sb{sub 40-x}S{sub 60} films (x=15, 20, 25 and 27). Chemical shifts of the constituent elements have revealed that electrons are transferred from chalcogenide to metal and compounds such as Ag{sub 2}S and Ag{sub 2}O are likely to foue to photo-induced chemical modification and oxidation, respectively. Charge defects are induced in the amorphous system.

  4. X-ray photoelectron spectroscopy studies of initial growth mechanism of CdTe layers grown on (100)GaAs by organometallic vapor phase epitaxy

    OpenAIRE

    1990-01-01

    Variations of the GaAs surface conditions and the adsorption of the precursor elements of Cd and Te on the (100)GaAs substrate were studied by x‐ray photoelectron spectroscopy at the initial stage of CdTe growth by organometallic vapor phase epitaxy. The stoichiometry of GaAs substrates was found to recover by annealing in the H2 environment (500°C, 5 min), while the surface was initially in an As‐rich condition after etching with H2SO4:H2O2:H2O (5:1:1). The preferential adsorption of Te on t...

  5. Electronic structure of β-Ga{sub 2}O{sub 3} single crystals investigated by hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guo-Ling [School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Zhang, Fabi; Guo, Qixin, E-mail: guoq@cc.saga-u.ac.jp [Synchrotron Light Application Center, Department of Electrical and Electronic Engineering, Saga University, Saga 840-8502 (Japan); Cui, Yi-Tao [Synchrotron Radiation Research Organization, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Oji, Hiroshi; Son, Jin-Young [Industrial Application Division, Japan Synchrotron Radiation Institute/SPring8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); SPring-8 Service Co., Ltd., 2-23-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1205 (Japan)

    2015-07-13

    By combination of hard X-ray photoelectron spectroscopy (HAXPES) and first-principles band structure calculations, the electronic states of β-Ga{sub 2}O{sub 3} were investigated to deepen the understanding of bulk information for this compound. The valence band spectra of HAXPES presented the main contribution from Ga 4sp, which are well represented by photoionization cross section weighted partial density of states. The experimental data complemented with the theoretical study yield a realistic picture of the electronic structure for β-Ga{sub 2}O{sub 3}.

  6. X-ray photoelectron spectroscopy and atomic force microscopy characterization of the effects of etching Zn xCd 1- xTe surfaces

    Science.gov (United States)

    George, M. A.; Azoulay, M.; Jayatirtha, H. N.; Burger, A.; Collins, W. E.; Silberman, E.

    1993-10-01

    X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was used for the first time to characterize the chemical composition of modified surfaces of Zn xCd 1- xTe single crystals. These surface treatments were selected for their relevance to device preparation procedures. The XPS peaks indicated an increase of the tellurium and a depletion of the cadmium concentrations upon etching in bromine methanol solution. AFM revealed the formation of pronounced Te inclusions. Higher x values correlated with a decrease in residual bromine left on the surface, while cut and polished samples had higher oxide concentrations and increased bromination of the surface than cleaved samples.

  7. Harmonium: A pulse preserving source of monochromatic extreme ultraviolet (30–110 eV) radiation for ultrafast photoelectron spectroscopy of liquids

    OpenAIRE

    2016-01-01

    A tuneable repetition rate extreme ultraviolet source (Harmonium) for time resolved photoelectron spectroscopy of liquids is presented. High harmonic generation produces 30-110 eV photons, with fluxes ranging from similar to 2 x 10(11) photons/s at 36 eV to similar to 2 x 10(8) photons/s at 100 eV. Four different gratings in a time-preserving grating monochromator provide either high energy resolution (0.2 eV) or high temporal resolution (40 fs) between 30 and 110 eV. Laser assisted photoemis...

  8. Examining the structural evolution of bicarbonate–water clusters: insights from photoelectron spectroscopy, basin-hopping structural search, and comparison with available IR spectral studies

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Hui [Chinese Academy of Sciences (CAS), Hefei (China). Lab. of Atmospheric Physico-Chemistry, Anhui Inst. of Optics & Fine Mechanics; Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division; Hou, Gao-Lei [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division; Liu, Yi-Rong [Chinese Academy of Sciences (CAS), Hefei (China). Lab. of Atmospheric Physico-Chemistry, Anhui Inst. of Optics & Fine Mechanics; Wang, Xue-Bin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division; Huang, Wei [Chinese Academy of Sciences (CAS), Hefei (China). Lab. of Atmospheric Physico-Chemistry, Anhui Inst. of Optics & Fine Mechanics; Univ. of Science and Technology of China, Hefei (China). School of Environmental Science & Optoelectronic Technology

    2016-05-31

    Bicarbonate serves a crucial biochemical role in the physiological pH buffering system and also has important atmospheric implications. In the current study, HCO3$-$(H2O)n (n = 0-13) clusters were successfully produced via electrospray ionization of corresponding bulk salt solution, and were characterized by combining negative ion photoelectron spectroscopy and theoretical calculations. The photoelectron spectra reveal that the electron binding energy monotonically increases with the cluster size up to n = 10 and remains largely the same after n > 10. The photo-detaching feature of the solute HCO3$-$itself, which dominates in the small clusters, diminishes with increase of water coverage. Based on the charge distribution and molecular orbital analyses, the universal high electron binding energy tail that dominates in the larger clusters can be attributed to ionization of water. Thus, the transition of ionization from solute to solvent at the size larger than n=10 has been observed. Extensive theoretical structural search based on the Basin-Hopping unbiased method was carried out, and a plethora of low energy isomers have been obtained for each medium and large size. By comparing the simulated photoelectron spectra and calculated electron binding energies with the experiments, as well as by comparing the simulated infrared spectra with previously reported IR spectra, the probable global minima and the structural evolutionary routes are presented. The nature of bicarbonate-water interactions are mainly electrostatic as implied by the electron localization function (ELF) analysis.

  9. Inner-valence states of N2(+) studied by UV photoelectron spectroscopy and configuration-interaction calculations

    Science.gov (United States)

    Baltzer, P.; Larsson, M.; Karlsson, L.; Wannberg, B.; Goethe, M. C.

    1992-11-01

    Spectrometric observations are conducted to examine the inner-valence photoelectron spectra of nitrogen molecules that are excited by He II. Spectra in the range 20-35 eV are studied by means of a UV source that provides high-resolution high-intensity readings for the radiation with a low photoionization cross section. Vibrational structures are reported in three electron bands related to cationic transitions, and a potential barrier towards dissociation is described. The three states of vibrational progression are given as C2Sigma(u)(+), D2Pi(g), and 3(2)Sigma(g)(+), and calculations of the same states are developed for comparison based on self-consistent-field and multireference configuration-interaction techniques. The present experimental and numerical results present data of interest in the interpretation of photoelectron spectroscopic astrophysical observations.

  10. X-ray photoelectron spectroscopy of Er{sup 3+}-activated SiO{sub 2}-HfO{sub 2} glass-ceramic waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Minati, L; Speranza, G; Micheli, V [FBK via Sommarive 18, Povo, 38100 Trento (Italy); Ferrari, M; Jestin, Y [CNR-IFN, Istituto di Fotonica e Nanotecnologie, CSMFO Lab., Via alla Cascata, 56/C, Povo, 38100 Trento (Italy)], E-mail: luminati@fbk.eu

    2009-01-07

    xHfO{sub 2}-(100 - x) SiO{sub 2} (x = 10, 20, 30 mol%) glass-ceramic planar waveguides doped with 0.3 mol% Er{sup 3+} ions, prepared by the sol-gel route and heat treated at 1000 deg. C to nucleate HfO{sub 2} crystals, were analysed by x-ray photoelectron spectroscopy, x-ray diffraction, high resolution transmission electron microscopy and photoluminescence spectroscopy. Formation of tetragonal HfO{sub 2} nanocrystals has been evidenced in all the samples. Spectroscopic parameters concerning the {sup 4}I{sub 13/2} metastable state of Er{sup 3+}ion are revisited as a function of XPS analysis.

  11. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses of the initial growth mechanism of CdTe layers on (100) GaAs by metalorganic vapor phase epitaxy

    OpenAIRE

    1990-01-01

    X‐ray photoelectron spectroscopy and Auger electron spectroscopy measurements were performed to investigate the initial growth mechanism and the selection of growth orientations of CdTe layers grown on (100) GaAs by metalorganic vapor phase epitaxy (MOVPE). The surface stoichiometry of the GaAs substrate was found to recover when annealed in a H2 flow atmosphere (500°C, 5 min), although the surface was initially in an As‐rich condition after chemical etching by H2SO4@B:H2O2@B:H2O=5@B:1@B:1. N...

  12. Local variation in Bi crystal sites of epitaxial GaAsBi studied by photoelectron spectroscopy and first-principles calculations

    Science.gov (United States)

    Laukkanen, P.; Punkkinen, M. P. J.; Lahti, A.; Puustinen, J.; Tuominen, M.; Hilska, J.; Mäkelä, J.; Dahl, J.; Yasir, M.; Kuzmin, M.; Osiecki, J. R.; Schulte, K.; Guina, M.; Kokko, K.

    2017-02-01

    Epitaxial Bi-containing III-V crystals (III-V1-xBix) have attracted increasing interest due to their potential in infrared applications. Atomic-scale characterization and engineering of bulk-like III-V1-xBix properties (e.g., Bi incorporation and defect formation) are challenging but relevant to develop applications. Toward that target, we report here that the traditional surface-science measurement of photoelectron spectroscopy (PES) is a potential, non-destructive method to be combined in the studies of bulk-like properties, when surface effects are properly removed. We have investigated epitaxial GaAs1-xBix films, capped by epitaxial AlAs layers, with high-resolution photoelectron spectroscopy. The Bi5d core-level spectra of GaAs1-xBix together with ab-initio calculations give direct evidence of variation of Bi bonding environment in the lattice sites. The result agrees with photoluminescence (PL) measurement which shows that the studied GaAs1-xBix films include local areas with higher Bi content, which contribute to PL but do not readily appear in x-ray diffraction (XRD). The measured and calculated Bi core-level shifts show also that Ga vacancies and Bi clusters are dominant defects.

  13. Strong-field ionization inducing multi-electron-hole coherence probed by attosecond pulses

    Science.gov (United States)

    Zhao, Jing; Yuan, Jianmin; Zhao, Zengxiu

    2016-05-01

    Recent advances in attosecond spectroscopy has enabled resolving electron-hole dynamics in real time. The correlated electron-hole dynamics and the resulted coherence are directly related to how fast the ionization is completed. How the laser-induced electron-hole coherence evolves and whether it can be utilized to probe the core dynamics are among the key questions in attosecond physics or even attosecond chemistry. In this work, we propose a new scenario to apply IR-pump-XUV-probe schemes to resolving strong field ionization induced and attosecond pulse driven electron-hole dynamics and coherence in real time. The coherent driving of both the infrared laser and the attosecond pulse correlates the dynamics of the core-hole and the valence-hole which leads to the otherwise forbidden absorption and emission of XUV photon. An analytical model is developed based on the strong-field approximation by taking into account of the essential multielectron configurations. The emission spectra from the core-valence transition and the core-hole recombination are found modulating strongly as functions of the time delay between the two pulses, which provides a unique insight into the instantaneous ionization and the interplay of the multi-electron-hole coherence.

  14. Spectroscopy

    CERN Document Server

    Walker, S

    1976-01-01

    The three volumes of Spectroscopy constitute the one comprehensive text available on the principles, practice and applications of spectroscopy. By giving full accounts of those spectroscopic techniques only recently introduced into student courses - such as Mössbauer spectroscopy and photoelectron spectroscopy - in addition to those techniques long recognised as being essential in chemistry teaching - sucha as e.s.r. and infrared spectroscopy - the book caters for the complete requirements of undergraduate students and at the same time provides a sound introduction to special topics for graduate students.

  15. Electron structure of excited configurations in Ca2V2O7 studied by electron-induced core-ionization loss spectroscopy, appearance-potential spectroscopy, and x-ray-photoelectron spectroscopy

    Science.gov (United States)

    Curelaru, I. M.; Strid, K.-G.; Suoninen, E.; Minni, E.; Rönnhult, T.

    1981-04-01

    We have measured the electron-induced core-ionization loss (CILS) spectra, the appearance-potential (APS) spectra, and the x-ray-photoelectron (XPS) spectra of Ca2V2O7, that is a prototype for a series of luminescent materials with general formula M2V2O7(M=Mg, Ca, Sr, Ba, Zn, Cd, Hg). From the analysis of the data provided by the edge spectroscopies (CILS and APS) and their comparison with the XPS binding energies, we deduced the electronic structure of the outer orbitals (occupied and empty) involved in these processes. Our data illustrate the strong many-body effects that occur in the excitation and decay of localized atomiclike configurations within the big ionic cluster V2O4-7. Excitation of core levels in calcium, outside the V2O4-7 ion, seems to involve more extended orbitals, since the screening is more efficient. Usefulness of complementary studies by x-ray emission and Auger electron spectroscopy is anticipated.

  16. An investigation of the electronic structure of some 3-monosubstituted-2-methylpropenes through computational chemistry and photoelectron spectroscopy

    Science.gov (United States)

    Schuquel, Ivânia T. A.; Ducati, Lucas C.; Custodio, Rogério; Rittner, Roberto; Klapstein, Dieter

    2008-06-01

    The photoelectron (PE) spectra of some 3-monosubstituted 2-methylpropenes H 2C dbnd C(CH 3)CH 2X [X = Cl, Br, I, OH, OMe, OEt, SH, SMe, SEt, N(Me) 2 and N(Et) 2] have been recorded. A preliminary analysis is presented indicating some trends in the ionization potentials associated with application of OVGF method and NBO analysis from MP2/6-31G(d,p) and cc-pVDZ level of theory indicating that the more effective hyperconjugation effect leads to the most stable conformers. The sensitivity of the outermost ionization energies of selected molecules with respect to the level of theory was analyzed. Application of the CASPT2 method with ANO basis set and geometries from MP2 calculations provided results in excellent agreement with the experimental data.

  17. Interference stabilization of autoionizing states in molecular $N_2$ studied by time- and angular-resolved photoelectron spectroscopy

    CERN Document Server

    Eckstein, Martin; Yang, Chung-Hsin; Sansone, Giuseppe; Vrakking, Marc J J; Ivanov, Misha; Kornilov, Oleg

    2016-01-01

    An autoionizing resonance in molecular N$_2$ is excited by an ultrashort XUV pulse and probed by a subsequent weak IR pulse, which ionizes the contributing Rydberg states. Time- and angular-resolved photoelectron spectra recorded with a velocity map imaging spectrometer reveal two electronic contributions with different angular distributions. One of them has an exponential decay rate of $20\\pm5$ fs, while the other one is shorter than 10 fs. This observation is interpreted as a manifestation of interference stabilization involving the two overlapping discrete Rydberg states. A formalism of interference stabilization for molecular ionization is developed and applied to describe the autoionizing resonance. The results of calculations reveal, that the effect of the interference stabilization is facilitated by rotationally-induced couplings of electronic states with different symmetry.

  18. Structural and X-Ray Photoelectron Spectroscopy Study of Al-Doped Zinc-Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    Bong Ju Lee

    2015-01-01

    Full Text Available Al-doped zinc-oxide (AZO thin films were prepared by RF magnetron sputtering at different oxygen partial pressures and substrate temperatures. The charge-carrier concentrations in the films decreased from 1.69 × 1021 to 6.16 × 1017 cm−3 with increased gas flow rate from 7 to 21 sccm. The X-ray diffraction (XRD patterns show that the (002/(103 peak-intensity ratio decreased as the gas flow rate increased, which was related to the increase of AZO thin film disorder. X-ray photoelectron spectra (XPS of the O1s were decomposed into metal oxide component (peak A and the adsorbed molecular oxygen on thin films (peak B. The area ratio of XPS peaks (A/B was clearly related to the stoichiometry of AZO films; that is, the higher value of A/B showed the higher stoichiometric properties.

  19. Photoelectron spectroscopy of mono-niobium carbide clusters NbCn-(n=2-7): Evidence for a cyclic to linear structural transition

    Science.gov (United States)

    Zhai, Hua-Jin; Liu, Shu-Rong; Li, Xi; Wang, Lai-Sheng

    2001-09-01

    We investigated a series of mono-niobium carbide clusters, NbCn- (n=2-7), using anion photoelectron spectroscopy. Vibrationally resolved photoelectron spectra were observed for NbC2- and NbC3-, which were both shown to have cyclic C2v structures. Two isomers were observed for NbC4- and NbC5-. The weak and low electron binding energy isomers were shown to be cyclic structures forming a series with NbC2- and NbC3-, and all have similar and low electron binding energies. The main isomers of NbC4- and NbC5-, which possess much higher electron binding energies, were shown to be due to linear structures, which form a series with NbC6- and NbC7-. All the linear NbCn- clusters were observed to have high electron binding energies and exhibit an even-odd alternation, similar to that observed for pure linear carbon clusters in the same size range. A cyclic to linear structural transition was thus observed for the NbCn- clusters from NbC3- to NbC4-, with the cyclic structures favored for the smaller clusters and the linear isomers favored for the larger clusters.

  20. X-ray photoelectron spectroscopy and diffraction investigation of a metal-oxide-semiconductor heterostructure: Pt/Gd2O3/Si(111)

    Science.gov (United States)

    Ferrah, D.; El Kazzi, M.; Niu, G.; Botella, C.; Penuelas, J.; Robach, Y.; Louahadj, L.; Bachelet, R.; Largeau, L.; Saint-Girons, G.; Liu, Q.; Vilquin, B.; Grenet, G.

    2015-04-01

    Platinum thin films deposited by physical vapor deposition (PVD) on Gd2O3/Si(111) templates are investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray photoelectron diffraction (XPD). Both XRD and XPD give clear evidence that Gd2O3 grows (111)-oriented and single-domain on Si(111) with mirror epitaxial relationship viz., [1bar10] Gd2O3(111)//[11bar0] Si(111). On Gd2O3/Si(111), Pt is partially crystallized with (111) orientation. There are two epitaxial domains and a slightly visible (111) fiber texture. The in-plane relationships of these Pt(111) domains with Gd2O3(111) are a direct one: [11bar0] Pt(111)//[11bar0] Gd2O3(111) and a mirror one: [1bar10] Pt(111)//[11bar0] Gd2O3(111). XPS reveals that Pt4f exhibits a metallic behavior even for small amounts of Pt but very small chemical shifts suggest that Pt environment is different at the interface with Gd2O3. These XPS chemical shifts have been correlated with features in XPD azimuth curves, which could be related with the existence of hexagonal α-PtO2(0001)layer.

  1. ZnO/ZnAl2O4 Nanocomposite Films Studied by X-Ray Diffraction, FTIR, and X-Ray Photoelectron Spectroscopy

    Directory of Open Access Journals (Sweden)

    S. Iaiche

    2015-01-01

    Full Text Available ZnO/ZnAl2O4 nanocomposite films were synthesised by ultrasonic spray pyrolysis (USP by extracting Al2O(SO42 oxide with zinc chloride hydrate in deionised water. The sample was then subjected to heat treatment at 650°C and 700°C for 1 h, which led to the formation of the spinel oxide (ZnAl2O4 and wurtzite (ZnO phases. Al2(SO43·18H2O salt was transformed into aluminum oxide sulfate Al2O(SO42, which is an intermediary decomposition product, by calcination at 795°C for 3 h. The structures of the synthesised ZnO/ZnAl2O4 films were confirmed by XRD, FTIR, and X-ray photoelectron spectroscopy (XPS. XPS spectra of the major Zn, Al, and O photoelectron lines and the major X-ray induced Zn LMM Auger lines for ZnO/ZnAl2O4 are presented.

  2. Time-resolved photoelectron spectroscopy of a dinuclear Pt(II) complex: Tunneling autodetachment from both singlet and triplet excited states of a molecular dianion

    Science.gov (United States)

    Winghart, Marc-Oliver; Yang, Ji-Ping; Vonderach, Matthias; Unterreiner, Andreas-Neil; Huang, Dao-Ling; Wang, Lai-Sheng; Kruppa, Sebastian; Riehn, Christoph; Kappes, Manfred M.

    2016-02-01

    Time-resolved pump-probe photoelectron spectroscopy has been used to study the relaxation dynamics of gaseous [Pt2(μ-P2O5H2)4 + 2H]2- after population of its first singlet excited state by 388 nm femtosecond laser irradiation. In contrast to the fluorescence and phosphorescence observed in condensed phase, a significant fraction of the photoexcited isolated dianions decays by electron loss to form the corresponding monoanions. Our transient photoelectron data reveal an ultrafast decay of the initially excited singlet 1A2u state and concomitant rise in population of the triplet 3A2u state, via sub-picosecond intersystem crossing (ISC). We find that both of the electronically excited states are metastably bound behind a repulsive Coulomb barrier and can decay via delayed autodetachment to yield electrons with characteristic kinetic energies. While excited state tunneling detachment (ESETD) from the singlet 1A2u state takes only a few picoseconds, ESETD from the triplet 3A2u state is much slower and proceeds on a time scale of hundreds of nanoseconds. The ISC rate in the gas phase is significantly higher than in solution, which can be rationalized in terms of changes to the energy dissipation mechanism in the absence of solvent molecules. [Pt2(μ-P2O5H2)4 + 2H]2- is the first example of a photoexcited multianion for which ESETD has been observed following ISC.

  3. Ionization of atoms by chirped attosecond pulses

    Institute of Scientific and Technical Information of China (English)

    Tan Fang; Peng Liang-You; Gong Qi-Huang

    2009-01-01

    We investigate the ionization dynamics of atoms by chirped attosecond pulses using the strong field approximation method. The pulse parameters are carefully chosen in the regime where the strong field approximation method is valid. We analyse the effects of the chirp of attosecond pulses on the energy distributions and the corresponding left-right asymmetry of the ionized electrons. For a single chirped attosecond pulse, the ionized electrons can be redistributed and the left-right asymmetry shows oscillations because of the introduction of the chirp. For time-delayed double attosecond pulses at different intensities with the weaker one chirped, exchanging the order of the two pulses shows a relative shift of the energy spectra, which can be explained by the different effective time delays of different frequency components because of the chirp.

  4. Time-resolved photoemission using attosecond streaking

    CERN Document Server

    Nagele, Stefan; Wais, Michael; Wachter, Georg; Burgdörfer, Joachim

    2014-01-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric effect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the field-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for effective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes $A$@$\\text{C}_{60}$ and discuss how streaking time shifts are modified due to the interaction of the $\\text{C}_...

  5. Time-resolved photoemission using attosecond streaking

    Science.gov (United States)

    Nagele, S.; Pazourek, R.; Wais, M.; Wachter, G.; Burgdörfer, J.

    2014-04-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric efect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the feld-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for efective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes A@C60 and discuss how streaking time shifts are modifed due to the interaction of the C60 cage with the probing infrared streaking field.

  6. Investigation of a metal-ionic conductor interface in thin film samples using X-ray photoelectron spectroscopy and electrical measurements

    Energy Technology Data Exchange (ETDEWEB)

    Couturier, G.; Danto, Y.; Barriere, A.S.; Duc, T.M.; Garaud, Y.

    1982-03-26

    The surface of an evaporated thin film of the ionic conductor ..beta..-PbF/sub 2/ was analysed using X-ray photoelectron spectroscopy (XPS). The results were compared with those obtained from nuclear and secondary ion mass spectrometry measurements. An analysis of the Au-..beta..-PbF/sub 2/ interface shows the presence of a thin layer of partly oxidized metallic lead. Part of this interfacial lead diffused across the gold film towards the external surface where it became bound to oxygen. An electrical analysis of the interface was performed by studying the capacitance as a function of the surface potential. The differences between experimental and calculated values are discussed in the light of the XPS measurements.

  7. Elucidating the electronic structure of supported gold nanoparticles and its relevance to catalysis by means of hard X-ray photoelectron spectroscopy

    Science.gov (United States)

    Reinecke, Benjamin N.; Kuhl, Kendra P.; Ogasawara, Hirohito; Li, Lin; Voss, Johannes; Abild-Pedersen, Frank; Nilsson, Anders; Jaramillo, Thomas F.

    2016-08-01

    We report on the electronic structure of Au (gold) nanoparticles supported onto TiO2 with a goal of elucidating the most important effects that contribute to their high catalytic activity. We synthesize and characterize with high resolution transmission electron microscopy (HRTEM) 3.4, 5.3, and 9.5 nm diameter TiO2-supported Au nanoparticles with nearly spherical shape and measure their valence band using Au 5d subshell sensitive hard X-ray photoelectron spectroscopy (HAXPES) conducted at Spring-8. Based on density functional theory (DFT) calculations of various Au surface structures, we interpret the observed changes in the Au 5d valence band structure as a function of size in terms of an increasing percentage of Au atoms at corners/edges for decreasing particle size. This work elucidates how Au coordination number impacts the electronic structure of Au nanoparticles, ultimately giving rise to their well-known catalytic activity.

  8. Band offsets of Er{sub 2}O{sub 3} films grown on Ge substrates by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Ting; Peng, Lining; Cui, Yanxia; Hao, Yuying [Taiyuan University of Technology, Key Laboratory of Advanced Transducers and Intelligent Control System (Ministry of Education), College of Physics and Optoelectronics, Taiyuan (China); Fang, Zebo [Shaoxing University, Department of Physics, Shaoxing (China)

    2014-06-15

    The band alignments of high-k Er{sub 2}O{sub 3} films grown on Ge substrates by molecular beam epitaxy are determined by X-ray photoelectron spectroscopy. The valenceband and the conduction-band offsets of Er{sub 2}O{sub 3} to Ge are found to be 3.16 ± 0.02 and 2.13 ± 0.02 eV, respectively. The energy gap of Er{sub 2}O{sub 3} is 5.96 ± 0.02 eV as determined by the optical spectrophotometry. From the band offset viewpoint, the above results indicate that Er{sub 2}O{sub 3} could be a promising candidate for high-k gate dielectrics on Ge substrate. (orig.)

  9. Harmonium: A pulse preserving source of monochromatic extreme ultraviolet (30–110 eV radiation for ultrafast photoelectron spectroscopy of liquids

    Directory of Open Access Journals (Sweden)

    J. Ojeda

    2016-03-01

    Full Text Available A tuneable repetition rate extreme ultraviolet source (Harmonium for time resolved photoelectron spectroscopy of liquids is presented. High harmonic generation produces 30–110 eV photons, with fluxes ranging from ∼2 × 1011 photons/s at 36 eV to ∼2 × 108 photons/s at 100 eV. Four different gratings in a time-preserving grating monochromator provide either high energy resolution (0.2 eV or high temporal resolution (40 fs between 30 and 110 eV. Laser assisted photoemission was used to measure the temporal response of the system. Vibrational progressions in gas phase water were measured demonstrating the ∼0.2 eV energy resolution.

  10. Thermodynamic Equilibrium Studies of Nanocrystallite CeO2 Grain Boundaries by High Temperature X-Ray Photoelectron Spectroscopy and Thermal Gravimetric Analysis

    Institute of Scientific and Technical Information of China (English)

    LIU Zhen-Xiang; XIE Kan

    2000-01-01

    Nanostructured CeO2 thin films and powders are studied by high temperature x-ray photoelectron spectroscopy and thermal gravimetric analysis. The results indicate that the surface composition strongly depends on temperature, the surface O/Ce ratio initially increases with increasing temperature, then decreases with the further increase of temperature, the maximum surface O/Ce ratio is at about 300℃ C. The variation of the surface composition with temperature arises from the ion migration, redistribution and transformation between lattice oxygen and gas phase oxygen near the grain boundaries during the thermodynamic equilibrium process. The results also show that CeO2 has a weakly bond oxygen, high oxygen mobility in the bulk and a high molecular dissociation rate at the surface, especially for the sol-gel prepared nanocrystallite CeO2.

  11. Structure, Mobility, and Composition of Transition Metal Catalyst Surfaces. High-Pressure Scanning Tunneling Microscopy and Ambient-Pressure X-ray Photoelectron Spectroscopy Studies

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhongwei [Univ. of California, Berkeley, CA (United States)

    2013-12-06

    Surface structure, mobility, and composition of transition metal catalysts were studied by high-pressure scanning tunneling microscopy (HP-STM) and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) at high gas pressures. HP-STM makes it possible to determine the atomic or molecular rearrangement at catalyst surfaces, particularly at the low-coordinated active surface sites. AP-XPS monitors changes in elemental composition and chemical states of catalysts in response to variations in gas environments. Stepped Pt and Cu single crystals, the hexagonally reconstructed Pt(100) single crystal, and Pt-based bimetallic nanoparticles with controlled size, shape and composition, were employed as the model catalysts for experiments in this thesis.

  12. Low-temperature scanning tunneling microscopy/ultraviolet photoelectron spectroscopy investigation of two-dimensional crystallization of C60: pentacence binary system on Ag(111)

    Science.gov (United States)

    Lin Zhang, Jia; Hong Liang Zhang, Kelvin; Qiang Zhong, Jian; Chao Niu, Tian; Chen, Wei

    2012-02-01

    Atomic scale investigation of temperature-dependent two-dimensional (2 D) crystallization processes of fullerene-C60 on pentacene-covered Ag(111) surface has been carried out by in situ low-temperature scanning tunneling microscopy (LT-STM) experiments. To evaluate the effect of molecule-substrate interfacial interactions on the 2 D crystallization of C60: pentacene binary system, we also carried out the same self-assembly experiments of C60 on monolayer pentacene covered graphite substrate. It is revealed that temperature-dependent structural transition of various ordered C60 nanoassemblies is strongly influenced by the molecule-Ag(111) interfacial interactions, and further mediated by the weak C60-pentacene intermolecular interactions. In situ ultraviolet photoelectron spectroscopy (UPS) has been used to evaluate the nature of the intermolecular interactions between C60 and pentacene films.

  13. High-resolution electron-energy-loss spectroscopy and photoelectron-diffraction studies of the geometric structure of adsorbates on single-crystal metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rosenblatt, D.H.

    1982-11-01

    Two techniques which have made important contributions to the understanding of surface phenomena are high resolution electron energy loss spectroscopy (EELS) and photoelectron diffraction (PD). EELS is capable of directly measuring the vibrational modes of clean and adsorbate covered metal surfaces. In this work, the design, construction, and performance of a new EELS spectrometer are described. These results are discussed in terms of possible structures of the O-Cu(001) system. Recommendations for improvements in this EELS spectrometer and guidelines for future spectrometers are given. PD experiments provide accurate quantitative information about the geometry of atoms and molecules adsorbed on metal surfaces. The technique has advantages when used to study disordered overlayers, molecular overlayers, multiple site systems, and adsorbates which are weak electron scatterers. Four experiments were carried out which exploit these advantages.

  14. The role of cesium suboxides in low-work-function surface layers studied by X-ray photoelectron spectroscopy - Ag-O-Cs

    Science.gov (United States)

    Yang, S.-J.; Bates, C. W., Jr.

    1980-01-01

    The oxidation of cesium on silver substrates has been studied using photoyield measurements and X-ray photoelectron spectroscopy. The occurrence of two O1s peaks in the core-level spectrum at 527.5 and 531.5-eV binding energy for cesium and oxygen exposures giving the optimum photoyield proves that two oxides of cesium exist in high-photoyield surfaces, and not Cs2O alone as previously thought. From the shape and position of the cesium peaks and the Auger parameter, the assignment of the O1s peaks at 527.5- and 531.5-eV binding energies to oxygen in Cs2O and Cs11O3, respectively, can be made. Hence the total cesium-oxygen layer is a mixed phase consisting of Cs2O + Cs11O3, approximately 20-40 A thick.

  15. Initial stages of ITO/Si interface formation: In situ x-ray photoelectron spectroscopy measurements upon magnetron sputtering and atomistic modelling using density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Løvvik, O. M.; Diplas, S.; Ulyashin, A. [SINTEF Materials and Chemistry, Forskningsveien 1, NO-0314 Oslo (Norway); Romanyuk, A. [University of Basel, Kingelbergstr. 82, CH-4056 Basel (Switzerland)

    2014-02-28

    Initial stages of indium tin oxide (ITO) growth on a polished Si substrate upon magnetron sputtering were studied experimentally using in-situ x-ray photoelectron spectroscopy measurements. The presence of pure indium and tin, as well as Si bonded to oxygen at the ITO/Si interface were observed. The experimental observations were compared with several atomistic models of ITO/Si interfaces. A periodic model of the ITO/Si interface was constructed, giving detailed information about the local environment at the interface. Molecular dynamics based on density functional theory was performed, showing how metal-oxygen bonds are broken on behalf of silicon-oxygen bonds. These theoretical results support and provide an explanation for the present as well as previous ex-situ and in-situ experimental observations pointing to the creation of metallic In and Sn along with the growth of SiO{sub x} at the ITO/Si interface.

  16. X-ray photoelectron spectroscopy of pyrrolidinium-based ionic liquids: cation-anion interactions and a comparison to imidazolium-based analogues.

    Science.gov (United States)

    Men, Shuang; Lovelock, Kevin R J; Licence, Peter

    2011-09-07

    We investigate seven 1-alkyl-1-methylpyrrolidinium-based ionic liquids, [C(n)C(1)Pyrr][X], using X-ray photoelectron spectroscopy (XPS). The electronic environment for each element is analysed and a robust fitting model is developed for the C 1s region that applies to each of the ionic liquids studied. This model allows accurate charge correction and the determination of reliable and reproducible binding energies for each ionic liquid studied. The electronic interaction between the cation and anion is investigated for ionic liquids with one and also two anions. i.e., mixtures. Comparisons are made to imidazolium-based ionic liquids; in particular, a detailed comparison is made between [C(8)C(1)Pyrr][X] and [C(8)C(1)Im][X](-), where X(¬) is common to both ionic liquids.

  17. Characterization of gate oxynitrides by means of time of flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy. Quantification of nitrogen

    CERN Document Server

    Ferrari, S; Fanciulli, M

    2002-01-01

    We present a methodology for the quantitative estimation of nitrogen in ultrathin oxynitrides by means of time of flight secondary ion mass spectrometry (TOF-SIMS) and x-ray photoelectron spectroscopy (XPS). We consider an innovative approach to TOF-SIMS depth profiling, by elemental distribution of single species as sum of peaks containing such species. This approach is very efficient in overcoming matrix effect arising when quantifying elements were distributed in silicon and silicon oxide. We use XPS to calibrate TOF-SIMS and to obtain quantitative information on nitrogen distribution in oxynitride thin layers. In the method we propose we process TOF-SIMS and XPS data simultaneously to obtain a quantitative depth profile.

  18. Evidence for chemical bond formation at rubber-brass interface: Photoelectron spectroscopy study of bonding interaction between copper sulfide and model molecules of natural rubber

    Science.gov (United States)

    Ozawa, Kenichi; Mase, Kazuhiko

    2016-12-01

    Strong adhesion between rubber and brass has been considered to arise mainly from the mechanical interaction, which is characterized by dendritic interlocking at the interface. In order to examine a possible contribution of the chemical interaction, chemical state analysis was carried out for model molecules of natural rubber (2-methyl-2-butene and isoprene) adsorbed on Cu2S, a key chemical species for adhesion, by means of photoelectron spectroscopy (PES). Absence of a C 1s PES component associated with C=C bonds and the appearance of adsorption-induced components in the S 2p region indicate that the molecules interact with the Cu2S surface via the C=C bond to form C-S covalent bonds. This proves that the chemical interaction certainly plays a role in rubber-brass adhesion along with the mechanical interaction.

  19. Structural and bonding properties of ScSi-n(n=2~6)clusters:photoelectron spectroscopy and density functional calculations

    Institute of Scientific and Technical Information of China (English)

    Xu Hong-Guang; Wu Miao-Miao; Zhang Zeng-Guang; Sun Qiang; Zheng Wei-Jun

    2011-01-01

    Anion ion photoelectron spectroscopy and density functional theory(DFT)are used to investigate the electronicand structural properties of ScSi-n(n=2~6)clusters and their neutrals. We find that the structures of ScSin are similar to those of Si-n+1. The most stable isomers of ScSin cluster anions and their neutrals are similar for n=2, 3and 5 but different for n=4 and 6, indicating that the charge effect on geometry is size dependent for small scandiumsilicon clusters. The low electron binding energy(EBE)tails observed in the spectra of ScSi-4,6 can be explained by the existence of less stable isomers. A comparison between ScSi-n and VSi-n clusters shows the effects of metal size and electron configuration on cluster geometries.

  20. X-ray absorption near the edge structure and x-ray photoelectron spectroscopy studies on pyrite prepared by thermally sulfurizing iron films

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui; Liu Ying-Shu; Wang Bao-Yi; Wei Long; Kui Re-Xi; Qian Hai-Jie

    2009-01-01

    This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by x-ray absorption near edge structure spectra and x-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.

  1. Characterisation of PEGylated PLGA nanoparticles comparing the nanoparticle bulk to the particle surface using UV/vis spectroscopy, SEC, {sup 1}H NMR spectroscopy, and X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Spek, S.; Haeuser, M. [Institute of Pharmaceutical Technology and Biopharmacy, University of Muenster, Corrensstrasse 48, 48149 Muenster (Germany); Schaefer, M.M. [nanoAnalytics, Heisenbergstrasse 11, 48149 Muenster (Germany); Langer, K., E-mail: k.langer@wwu.de [Institute of Pharmaceutical Technology and Biopharmacy, University of Muenster, Corrensstrasse 48, 48149 Muenster (Germany)

    2015-08-30

    Graphical abstract: - Highlights: • We compared nanoparticles prepared on the basis of PLGA and PEG–PLGA for their polymeric composition in the particle bulk and on the surface. • We validated three analytical methods (UV/vis, SEC, {sup 1}H NMR) for quantification of the polymeric stabiliser PVA and {sup 1}H NMR for the quantification of PEG. • In the case of PEG–PLGA as starting material we observed significant PEG contents not only on the surface but even in the particle bulk. • We observed an unexpected accumulation of the polymeric stabiliser PVA on PEGylated particle surfaces. - Abstract: Hypothesis: The bulk and the surface structure of nanoparticles based on poly(lactic-co-glycolic acid) (PLGA) and PLGA–PEG copolymer is expected to consist of different polymer compositions. An enrichment of hydrophilic PEG on the surface in combination with an accumulation of PLGA in the bulk is anticipated. Hence, the imbalance between bulk and surface composition should be detectable by suitable analytical methods. Experiments: Nanoparticles were assembled using an emulsion-evaporation method with polyvinyl alcohol (PVA) as stabiliser. Mixtures of PLGA and PLGA–PEG copolymer were applied to achieve variably PEGylated nanoparticles. The nanoparticle composition was analysed with respect to PLGA, PVA and PEG, comparing the polymer content of the nanoparticle bulk to the surface. For the bulk, PVA was quantified by a UV/vis spectroscopic method as well as size exclusion chromatography (SEC), and {sup 1}H nuclear magnetic resonance (NMR) spectroscopy. PEG determination of the bulk was carried out using quantitative {sup 1}H NMR spectroscopy. Surface composition was investigated by X-ray photoelectron spectroscopy (XPS). Findings: For the characterisation of the polymer composition {sup 1}H NMR, SEC, and XPS-methods were successfully established and validated. Unexpectedly, a significant PEG content was detected within the particle bulk. The comparison of

  2. Optical vortices discern attosecond time delay in electron emission from magnetic sublevels

    CERN Document Server

    Wätzel, Jonas

    2016-01-01

    Photoionization from energetically distinct electronic states may have a relative time delay of tens of attoseconds. Here we demonstrate that pulses of optical vortices allow measuring such attoseconds delays from magnetic sublevels, even from a spherically symmetric target. The di?erence in the time delay is substantial and exhibits a strong angular dependence. Furthermore, we find an atomic scale variation in the time delays depending on the target orbital position in the laser spot. The findings o?er thus a qualitatively new way for a spatio-temporal sensing of the magnetic states from which the photoelectrons originate, with a spatial resolution way below the di?raction limit of the vortex beam. Our conclusions follow from analytical considerations based on symmetry, complemented and confirmed with full numerical simulations of the quantum dynamics.

  3. Photoelectron spectroscopy investigation of the temperature-induced deprotonation and substrate-mediated hydrogen transfer in a hydroxyphenyl-substituted porphyrin

    Energy Technology Data Exchange (ETDEWEB)

    Smykalla, Lars, E-mail: lars.smykalla@physik.tu-chemnitz.de [Technische Universität Chemnitz, Institute of Physics, Solid Surfaces Analysis Group, D-09107 Chemnitz (Germany); Shukrynau, Pavel [Technische Universität Chemnitz, Institute of Physics, Solid Surfaces Analysis Group, D-09107 Chemnitz (Germany); Mende, Carola; Lang, Heinrich [Technische Universität Chemnitz, Institute of Chemistry, Inorganic Chemistry, D-09107 Chemnitz (Germany); Knupfer, Martin [Electronic and Optical Properties Department, IFW Dresden, D-01171 Dresden (Germany); Hietschold, Michael [Technische Universität Chemnitz, Institute of Physics, Solid Surfaces Analysis Group, D-09107 Chemnitz (Germany)

    2015-04-01

    Highlights: • Photoelectron spectroscopy of tetra(p-hydroxyphenyl)porphyrin on Au(1 1 1) and Ag(1 1 0). • Ratio of amount of −NH− to −N= in the molecule on Au(1 1 1) decreases after annealing. • Dissociation of −OH groups and transfer of hydrogen atoms to −N= on Ag(1 1 0). • Cleavage of C−H bonds of porphyrin macro-cycle at high temperature. • Changes of the valence band of the molecule in dependance of annealing temperature. - Abstract: The temperature dependent stepwise deprotonation of 5,10,15,20-tetra(p-hydroxyphenyl)-porphyrin is investigated using photoelectron spectroscopy. An abundance of pyrrolic relative to iminic nitrogen and a decrease in the ratio of the amount of −NH− to −N= with increasing annealing temperature is found. In contrast to the molecules adsorbed on Au(1 1 1), on the more reactive Ag(1 1 0) surface, partial dissociation of the hydroxyl groups and subsequent diffusion and rebonding of hydrogen to the central nitrogen atoms resulting in a zwitterionic molecule was clearly observed. Moreover, partial C−H bond cleavage and the formation of new covalent bonds with adjacent molecules or the surface starts at a relatively high annealing temperature of 300 °C. This reaction is identified to occur at the carbon atoms of the pyrrole rings, which leads also to a shift in the N 1s signal and changes in the valence band of the molecules. Our results show that annealing can significantly alter the molecules which were deposited depending on the maximum temperature and the catalytic properties of the specific substrate. The thermal stability should be considered if a molecular monolayer is prepared from a multilayer by desorption, or if annealing is applied to enhance the self-assembly of molecular structures.

  4. The influence of biosurfactant adsorption on the physicochemical behaviour of carbon steel surfaces using contact angle measurements and X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Shubina, V., E-mail: varvara.shubina2014@gmail.com [LUNAM Université, IFSTTAR, MAST, SMC, F-44340 Bouguenais (France); Gaillet, L. [LUNAM Université, IFSTTAR, MAST, SMC, F-44340 Bouguenais (France); Ababou-Girard, S. [Institut de Physique de Rennes, Département Matériaux et Nanosciences, UMR 6251 CNRS, Université Rennes 1, 35000 Rennes-Cedex (France); Gaudefroy, V. [LUNAM Université, IFSTTAR, MAST, SMC, F-44340 Bouguenais (France); Chaussadent, T.; Farças, F. [Université Paris-Est, IFSTTAR, MAST, CPDM, F-77447 Marne-la-Vallée (France); Meylheuc, T. [INRA, UMR1319 Micalis, F-78352 Jouy-en-Josas (France); AgroParisTech, UMR Micalis, F-78352 Jouy-en-Josas (France); Dagbert, C. [2 Chemin de la Grand’côte, 36270 Éguzon-Chantôme (France); Creus, J. [LaSIE, UMR7356, Université de La Rochelle, Pôle Sciences et Technologie, Bâtiment Marie Curie, Avenue Michel Crépeau, 17000 La Rochelle (France)

    2015-10-01

    Highlights: • Surface modifications to carbon steel surfaces due to the adsorption of a biosurfactant derived from Pseudomonas fluorescens bacteria cells were investigated using contact angle measurements (CAM) and X-ray photoelectron spectroscopy (XPS). • CAM allowed to establish an increase of electron-donating properties of steel surface due to the biosurfactant adsorption. • XPS demonstrated that biosurfactant molecules change the stoichiometry of mixted-oxide layer and the new outer layer mostly composed of magnetite. • Thickness and density of adsorbed biosurfactants layers were highlighted using a semiquantitative approach for 3 different concentrations of biomolecules. - Abstract: We investigated modifications to carbon steel surfaces due to the adsorption of a biosurfactant derived from Pseudomonas fluorescens bacteria cells using contact angle measurements (CAM) and X-ray photoelectron spectroscopy (XPS). After conditioning carbon steel in solutions with three different concentrations of biosurfactant molecules: 0.05, 0.3 and 1 g L{sup −1}, the average thickness of the biosurfactant layer on the carbon steel specimens was 7.9 ± 0.3, 12.1 ± 0.5 and 16.4 ± 0.7 Å, respectively. The biosurfactants changed the composition of both the Fe{sup 2+} and Fe{sup 3+} mixed-oxide layer and the outer layer, mostly composed of Fe{sup 3+} associated with magnetite. Contact angle measurements indicate decreased hydrophobic properties after the carbon steel was modified by biosurfactant. It was shown that the carbon steel surface free energy depends on the biosurfactant concentration, due to an acquisition of strong electron-donating properties.

  5. High resolution pulsed field ionization photoelectron spectroscopy using multibunch synchrotron radiation: Time-of-flight selection scheme

    Energy Technology Data Exchange (ETDEWEB)

    Jarvis, G.K. [Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Song, Y.; Ng, C.Y. [Ames Laboratory, United States Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)

    1999-06-01

    We have developed an efficient electron time-of-flight (TOF) selection scheme for high resolution pulsed field ionization (PFI) photoelectron (PFI-PE) measurements using monochromatized multibunch undulator synchrotron radiation at the Advanced Light Source. By employing a simple electron TOF spectrometer, we show that PFI-PEs produced by the PFI in the dark gap of a synchrotron ring period can be cleanly separated from prompt background photoelectrons. A near complete suppression of prompt electrons was achieved in PFI-PE measurements by gating the PFI-PE TOF peak, as indicated by monitoring background electron counts at the Ar(11s{sup {prime}}) autoionizing Rydberg peak, which is adjacent to the Ar{sup +}({sup 2}P{sub 3/2}) PFI-PE band. The rotational-resolved PFI-PE band for H{sub 2}{sup +} (X {sup 2}{Sigma}{sub g}{sup +},v{sup +}=0) measured using this electron TOF selection scheme is nearly free from residues of nearby autoionizing features, which were observed in the previous measurement by employing an electron spectrometer equipped with a hemispherical energy analyzer. This comparison indicates that the TOF PFI-PE scheme is significantly more effective in suppressing the hot-electron background. In addition to attaining a high PFI-PE transmission, a major advantage of the electron TOF scheme is that it allows the use of a smaller pulsed electric field and thus results in a higher instrumental PFI-PE resolution. We have demonstrated instrumental resolutions of 1.0 cm{sup {minus}1} full width at half maximum (FWHM) and 1.9 cm{sup {minus}1} FWHM in the PFI-PE bands for Xe{sup +}({sup 2}P{sub 3/2}) and Ar{sup +}({sup 2}P{sub 3/2}) at 12.123 and 15.760 eV, respectively. These resolutions are more than a factor 2 better than those achieved in previous synchrotron based PFI-PE studies. {copyright} {ital 1999 American Institute of Physics.}

  6. Negative Ion Photoelectron Spectroscopy Reveals Thermodynamic Advantage of Organic Acids in Facilitating Formation of Bisulfate Ion Clusters: Atmospheric Implications

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Gao-Lei; Lin, Wei; Deng, Shihu; Zhang, Jian; Zheng, Weijun; Paesani, Francesco; Wang, Xue B.

    2013-03-07

    Recent lab and field measurements have indicated critical roles of organic acids in enhancing new atmospheric aerosol formation. Such findings have stimulated theoretical studies with the aim of understanding interaction of organic acids with common aerosol nucleation precursors like bisulfate (HSO4-). In this Letter, we report a combined negative ion photoelectron spectroscopic and theoretical investigation of molecular clusters formed by HSO4- with succinic acid (SUA, HO2C(CH2)2CO2H), HSO4-(SUA)n (n = 0-2), along with HSO4-(H2O)n and HSO4-(H2SO4)n. It is found that one SUA molecule can stabilize HSO4- by ca. 39 kcal/mol, triple the corresponding value that one water molecule is capable of (ca. 13 kcal/mol). Molecular dynamics simulations and quantum chemical calculations reveal the most plausible structures of these clusters and attribute the stability of these clusters due to formation of strong hydrogen bonds. This work provides direct experimental evidence showing significant thermodynamic advantage by involving organic acid molecules to promote formation and growth in bisulfate clusters and aerosols.

  7. Surface spin-polarized currents generated in topological insulators by circularly polarized synchrotron radiation and their photoelectron spectroscopy indication

    Science.gov (United States)

    Shikin, A. M.; Klimovskikh, I. I.; Filyanina, M. V.; Rybkina, A. A.; Pudikov, D. A.; Kokh, K. A.; Tereshchenko, O. E.

    2016-08-01

    A new method for generating spin-polarized currents in topological insulators has been proposed and investigated. The method is associated with the spin-dependent asymmetry of the generation of holes at the Fermi level for branches of topological surface states with the opposite spin orientation under the circularly polarized synchrotron radiation. The result of the generation of holes is the formation of compensating spin-polarized currents, the value of which is determined by the concentration of the generated holes and depends on the specific features of the electronic and spin structures of the system. The indicator of the formed spin-polarized current can be a shift of the Fermi edge in the photoelectron spectra upon photoexcitation by synchrotron radiation with the opposite circular polarization. The topological insulators with different stoichiometric compositions (Bi1.5Sb0.5Te1.8Se1.2 and PbBi2Se2Te2) have been investigated. It has been found that there is a correlation in the shifts and generated spin-polarized currents with the specific features of the electronic spin structure. Investigations of the graphene/Pt(111) system have demonstrated the possibility of using this method for other systems with a spin-polarized electronic structure.

  8. Electronic structure and spectroscopy of nucleic acid bases: Ionization energies, ionization-induced structural changes, and photoelectron spectra

    Energy Technology Data Exchange (ETDEWEB)

    Bravaya, Ksenia B.; Kostko, Oleg; Dolgikh, Stanislav; Landau, Arie; Ahmed, Musahid; Krylov, Anna I.

    2010-08-02

    We report high-level ab initio calculations and single-photon ionization mass spectrometry study of ionization of adenine (A), thymine (T), cytosine (C) and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized five lowest-energy tautomeric forms. The first adiabatic and several vertical ionization energies were computed using equation-of-motion coupled-cluster method for ionization potentials with single and double substitutions. Equilibrium structures of the cationic ground states were characterized by DFT with the {omega}B97X-D functional. The ionization-induced geometry changes of the bases are consistent with the shapes of the corresponding molecular orbitals. For the lowest-energy tautomers, the magnitude of the structural relaxation decreases in the following series G > C > A > T, the respective relaxation energies being 0.41, 0.32, 0.25 and 0.20 eV. The computed adiabatic ionization energies (8.13, 8.89, 8.51-8.67 and 7.75-7.87 eV for A,T,C and G, respectively) agree well with the onsets of the photoionization efficiency (PIE) curves (8.20 {+-} 0.05, 8.95 {+-} 0.05, 8.60 {+-} 0.05 and 7.75 {+-} 0.05 eV). Vibrational progressions for the S{sub 0}-D{sub 0} vibronic bands computed within double-harmonic approximation with Duschinsky rotations are compared with previously reported experimental photoelectron spectra.

  9. Geometrical and Electronic Structures of MnS3(-/0) Clusters from Computational Chemistry and Photoelectron Spectroscopy.

    Science.gov (United States)

    Tran, Van Tan; Tran, Quoc Tri

    2016-05-26

    The B3LYP functional and CASPT2 method have been applied to investigate the geometrical and electronic structures of η(2)-(S2)MnS(-/0), η(2)-(S3)Mn(-/0), and MnS3(-/0) isomers of MnS3(-/0) clusters. The ground state of the anionic cluster is computed to be the (5)B2 of η(2)-(S2)MnS(-) isomer, whereas that of the anionic cluster is calculated to be the (4)B1 of the same isomer. The photoelectron spectrum of MnS3(-) cluster is interpreted by electron detachment processes from the most stable η(2)-(S2)MnS(-) and from the metastable η(2)-(S3)Mn(-) and MnS3(-) isomers. The first and second bands with low intensities are, respectively, attributed to the (7)A' → (6)A' and (7)A' → (8)A' transitions within the η(2)-(S3)Mn(-/0) isomers. The third band with the highest intensity in the spectrum can be assigned to the (5)B2 → (4)B1, (5)B2 → (6)B1, and (5)B2 → (4)A2 transitions within the most stable η(2)-(S2)MnS(-/0) isomers, the (3)B1 → (2)A1 transition within the metastable MnS3(-/0) isomers, and the (7)A' → 3(6)A' transition within the metastable η(2)-(S3)Mn(-/0) isomers. Because the η(2)-(S2)MnS(-) is computed to be the most stable isomer of the MnS3(-) cluster, we believe that the highest intensity third band in the spectrum is mainly the result of electron detachments from this isomer.

  10. Attosecond dynamics of electrons in molecules and liquids

    Science.gov (United States)

    Woerner, Hans Jakob

    2016-05-01

    The ultrafast motion of electrons and holes following light-matter interaction is fundamental to a broad range of chemical and biophysical processes. In this lecture, I will discuss two recent experiments carried out in our group that measure the atomic-scale motion of charge with attosecond temporal resolution (1 as = 10-18 s). The first experiment is carried out on isolated, spatially oriented molecules in the gas phase. We advance high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately following ionization of iodoacetylene, while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement of both even and odd harmonic orders, enables us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~ 100 as. We separately reconstruct quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determine the shape of the hole created by ionization. The second experiment is carried out on a free-flowing microjet of liquid water. We use an attosecond pulse train synchronized with a near-infrared laser pulse to temporally resolve the process of photoemission from liquid water using the RABBIT technique. We measure a delay on the order of 50 as between electrons emitted from the HOMO of liquid water compared to that of gas-phase water and a substantially reduced modulation contrast of the corresponding sidebands. Since our measurements on solvated water molecules are referenced to isolated ones, the measured delays reflect (i) the photoionization delays caused by electron transport through the aqueous environment and (ii) the effect of solvation on the parent molecule. The relative modulation contrast, in turn, contains information on (iii) the modification of transition amplitudes and (iv) dephasing processes. These experiments make the liquid phase and its fascinating

  11. Temperature-dependent Raman and ultraviolet photoelectron spectroscopy studies on phase transition behavior of VO{sub 2} films with M1 and M2 phases

    Energy Technology Data Exchange (ETDEWEB)

    Okimura, Kunio, E-mail: okifn@keyaki.cc.u-tokai.ac.jp; Hanis Azhan, Nurul [Graduate School of Engineering, Tokai University, Hiratsuka 259-1292 (Japan); Hajiri, Tetsuya [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Kimura, Shin-ichi [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871 (Japan); Zaghrioui, Mustapha; Sakai, Joe [GREMAN, UMR 7347 CNRS, Université François Rabelais de Tours, Parc de Grandmont, 37200 Tours (France)

    2014-04-21

    Structural and electronic phase transitions behavior of two polycrystalline VO{sub 2} films, one with pure M1 phase and the other with pure M2 phase at room temperature, were investigated by temperature-controlled Raman spectroscopy and ultraviolet photoelectron spectroscopy (UPS). We observed characteristic transient dynamics in which the Raman modes at 195 cm{sup −1} (V-V vibration) and 616 cm{sup −1} (V-O vibration) showed remarkable hardening along the temperature in M1 phase film, indicating the rearrangements of V-V pairs and VO{sub 6} octahedra. It was also shown that the M1 Raman mode frequency approached those of invariant M2 peaks before entering rutile phase. In UPS spectra with high energy resolution of 0.03 eV for the M2 phase film, narrower V{sub 3d} band was observed together with smaller gap compared to those of M1 phase film, supporting the nature of Mott insulator of M2 phase even in the polycrystalline film. Cooperative behavior of lattice rearrangements and electronic phase transition was suggested for M1 phase film.

  12. The initial atomic layer deposition of HfO2/Si(001) as followed in situ by synchrotron radiation photoelectron spectroscopy

    Science.gov (United States)

    Tallarida, Massimo; Karavaev, Konstantin; Schmeisser, Dieter

    2008-09-01

    We have grown HfO2 on Si(001) by atomic layer deposition (ALD) using HfCl4 and H2O as precursors. The early stages of the ALD were investigated with high-resolution photoelectron spectroscopy and x-ray absorption spectroscopy. We observed the changes occurring in the Si2p, O1s, Hf4f, Hf4d, and Cl2p core level lines after each ALD cycle up to the complete formation of two layers of HfO2. From the analysis of those variations, we deduced the growth properties of HfO2. The first layer consists of a sparse and Cl-contaminated oxide because of the incomplete oxidation, and the second layer is denser than the first one and with an almost stoichiometric O /Hf ratio. At the completion of the second layer, the x-ray absorption spectra revealed the change of the Hf-oxide chemical state due to the transition from the thin Hf-oxide to the bulklike HfO2.

  13. Degradation of all-vanadium redox flow batteries (VRFB) investigated by electrochemical impedance and X-ray photoelectron spectroscopy: Part 2 electrochemical degradation

    Science.gov (United States)

    Derr, Igor; Bruns, Michael; Langner, Joachim; Fetyan, Abdulmonem; Melke, Julia; Roth, Christina

    2016-09-01

    Electrochemical degradation (ED) of carbon felt electrodes was investigated by cycling of a flow through all-vanadium redox flow battery (VRFB) and conducting half-cell measurements with two reference electrodes inside the test bench. ED was detected using half-cell and full-cell electrochemical impedance spectroscopy (EIS) at different states of charge (SOC). Reversing the polarity of the battery to recover cell performance was performed with little success. Renewing the electrolyte after a certain amount of cycles restored the capacity of the battery. X-ray photoelectron spectroscopy (XPS) reveals that the amount of surface functional increases by more than a factor of 3 for the negative side as well as for the positive side. Scanning electron microscope (SEM) images show a peeling of the fiber surface after cycling the felts, which leads to a loss of electrochemically active surface area (ECSA). Long term cycling shows that ED has a stronger impact on the negative half-cell [V(II)/V(III)] than the positive half-cell [V(IV)/V(V)] and that the negative half-cell is the rate-determining half-cell for the VRFB.

  14. X-ray Photoelectron Spectroscopy ofGaP_{1-x}N_x Photocorroded as a Result of Hydrogen Productionthrough Water Electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Marie A.; /Illinois U., Urbana /SLAC

    2006-09-27

    Photoelectrochemical (PEC) cells produce hydrogen gas through the sunlight driven electrolysis of water. By extracting hydrogen and oxygen from water and storing solar energy in the H-H bond, they offer a promising renewable energy technology. Addition of dilute amounts of nitrogen to III-V semiconductors has been shown to dramatically increase the stability of these materials for hydrogen production. In an effort to learn more about the origin of semiconductor photocorrosion in PEC cells, three samples of p-type GaP with varying levels of nitrogen content (0%, 0.2%, 2%) were photocorroded and examined by X-ray Photoelectron Spectroscopy (XPS). GaPN samples were observed to be more efficient during the hydrogen production process than the pure GaP samples. Sample surfaces contained gallium oxides in the form of Ga{sub 2}O{sub 3} and Ga(OH){sub 3} and phosphorus oxide (P{sub 2}O{sub 5}), as well as surface oxides from exposure to air. A significant shift in intensity from bulk to surface peaks dramatic nitrogen segregation to the surface during photoelectrochemical hydrogen production. Further investigations, including using a scanning electron microscope to investigate sample topography and inductively coupled plasma mass spectroscopy (ICP-MS) analysis for solution analyses, are under way to determine the mechanism for these changes.

  15. Time-resolved photoelectron spectroscopy of a dinuclear Pt(II) complex: Tunneling autodetachment from both singlet and triplet excited states of a molecular dianion

    Energy Technology Data Exchange (ETDEWEB)

    Winghart, Marc-Oliver, E-mail: marc-oliver.winghart@kit.edu; Unterreiner, Andreas-Neil [Institute of Physical Chemistry, Karlsruhe Institute of Technology, P.O. Box 6980, 76049 Karlsruhe (Germany); Yang, Ji-Ping [Institute of Physical Chemistry, Karlsruhe Institute of Technology, P.O. Box 6980, 76049 Karlsruhe (Germany); School of Sciences, Hefei University of Technology, Hefei 230009 (China); Vonderach, Matthias [Centre for Proteome Research, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB (United Kingdom); Huang, Dao-Ling; Wang, Lai-Sheng [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Kruppa, Sebastian; Riehn, Christoph [Fachbereich Chemie und Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 52–54, 67663 Kaiserslautern (Germany); Kappes, Manfred M., E-mail: manfred.kappes@kit.edu [Institute of Physical Chemistry, Karlsruhe Institute of Technology, P.O. Box 6980, 76049 Karlsruhe (Germany); Institute of Nanotechnology, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe (Germany)

    2016-02-07

    Time-resolved pump-probe photoelectron spectroscopy has been used to study the relaxation dynamics of gaseous [Pt{sub 2}(μ-P{sub 2}O{sub 5}H{sub 2}){sub 4} + 2H]{sup 2−} after population of its first singlet excited state by 388 nm femtosecond laser irradiation. In contrast to the fluorescence and phosphorescence observed in condensed phase, a significant fraction of the photoexcited isolated dianions decays by electron loss to form the corresponding monoanions. Our transient photoelectron data reveal an ultrafast decay of the initially excited singlet {sup 1}A{sub 2u} state and concomitant rise in population of the triplet {sup 3}A{sub 2u} state, via sub-picosecond intersystem crossing (ISC). We find that both of the electronically excited states are metastably bound behind a repulsive Coulomb barrier and can decay via delayed autodetachment to yield electrons with characteristic kinetic energies. While excited state tunneling detachment (ESETD) from the singlet {sup 1}A{sub 2u} state takes only a few picoseconds, ESETD from the triplet {sup 3}A{sub 2u} state is much slower and proceeds on a time scale of hundreds of nanoseconds. The ISC rate in the gas phase is significantly higher than in solution, which can be rationalized in terms of changes to the energy dissipation mechanism in the absence of solvent molecules. [Pt{sub 2}(μ-P{sub 2}O{sub 5}H{sub 2}){sub 4} + 2H]{sup 2−} is the first example of a photoexcited multianion for which ESETD has been observed following ISC.

  16. Charge-transfer-to-solvent reactions from I- to water, methanol, and ethanol studied by time-resolved photoelectron spectroscopy of liquids

    Science.gov (United States)

    Okuyama, Haruki; Suzuki, Yoshi-Ichi; Karashima, Shutaro; Suzuki, Toshinori

    2016-08-01

    The charge-transfer-to-solvent (CTTS) reactions from iodide (I-) to H2O, D2O, methanol, and ethanol were studied by time-resolved photoelectron spectroscopy of liquid microjets using a magnetic bottle time-of-flight spectrometer with variable pass energy. Photoexcited iodide dissociates into a weak complex (a contact pair) of a solvated electron and an iodine atom in similar reaction times, 0.3 ps in H2O and D2O and 0.5 ps in methanol and ethanol, which are much shorter than their dielectric relaxation times. The results indicate that solvated electrons are formed with minimal solvent reorganization in the long-range solvent polarization field created for I-. The photoelectron spectra for CTTS in H2O and D2O—measured with higher accuracy than in our previous study [Y. I. Suzuki et al., Chem. Sci. 2, 1094 (2011)]—indicate that internal conversion yields from the photoexcited I-* (CTTS) state are less than 10%, while alcohols provide 2-3 times greater yields of internal conversion from I-*. The overall geminate recombination yields are found to be in the order of H2O > D2O > methanol > ethanol, which is opposite to the order of the mutual diffusion rates of an iodine atom and a solvated electron. This result is consistent with the transition state theory for an adiabatic outer-sphere electron transfer process, which predicts that the recombination reaction rate has a pre-exponential factor inversely proportional to a longitudinal solvent relaxation time.

  17. Charge-transfer-to-solvent reactions from I(-) to water, methanol, and ethanol studied by time-resolved photoelectron spectroscopy of liquids.

    Science.gov (United States)

    Okuyama, Haruki; Suzuki, Yoshi-Ichi; Karashima, Shutaro; Suzuki, Toshinori

    2016-08-21

    The charge-transfer-to-solvent (CTTS) reactions from iodide (I(-)) to H2O, D2O, methanol, and ethanol were studied by time-resolved photoelectron spectroscopy of liquid microjets using a magnetic bottle time-of-flight spectrometer with variable pass energy. Photoexcited iodide dissociates into a weak complex (a contact pair) of a solvated electron and an iodine atom in similar reaction times, 0.3 ps in H2O and D2O and 0.5 ps in methanol and ethanol, which are much shorter than their dielectric relaxation times. The results indicate that solvated electrons are formed with minimal solvent reorganization in the long-range solvent polarization field created for I(-). The photoelectron spectra for CTTS in H2O and D2O-measured with higher accuracy than in our previous study [Y. I. Suzuki et al., Chem. Sci. 2, 1094 (2011)]-indicate that internal conversion yields from the photoexcited I(-*) (CTTS) state are less than 10%, while alcohols provide 2-3 times greater yields of internal conversion from I(-*). The overall geminate recombination yields are found to be in the order of H2O > D2O > methanol > ethanol, which is opposite to the order of the mutual diffusion rates of an iodine atom and a solvated electron. This result is consistent with the transition state theory for an adiabatic outer-sphere electron transfer process, which predicts that the recombination reaction rate has a pre-exponential factor inversely proportional to a longitudinal solvent relaxation time.

  18. Measurement of valence-band offset at native oxide/BaSi{sub 2} interfaces by hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takabe, Ryota; Du, Weijie; Takeuchi, Hiroki; Toko, Kaoru [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Ito, Keita [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Japan Society for the Promotion of Science (JSPS), Chiyoda, Tokyo 102-0083 (Japan); Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Ueda, Shigenori [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), Hyogo 679-5148 (Japan); Quantum Beam Unit, NIMS, Tsukuba, Ibaraki 305-0047 (Japan); Kimura, Akio [Graduate School of Science, Hiroshima University, Higashi-hiroshima 739-8526 (Japan); Suemasu, Takashi [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Japan Science and Technology Agency, CREST, Tokyo 102-0075 (Japan)

    2016-01-14

    Undoped n-type BaSi{sub 2} films were grown on Si(111) by molecular beam epitaxy, and the valence band (VB) offset at the interface between the BaSi{sub 2} and its native oxide was measured by hard x-ray photoelectron spectroscopy (HAXPES) at room temperature. HAXPES enabled us to investigate the electronic states of the buried BaSi{sub 2} layer non-destructively thanks to its large analysis depth. We performed the depth-analysis by varying the take-off angle (TOA) of photoelectrons as 15°, 30°, and 90° with respect to the sample surface and succeeded to obtain the VB spectra of the BaSi{sub 2} and the native oxide separately. The VB maximum was located at −1.0 eV from the Fermi energy for the BaSi{sub 2} and −4.9 eV for the native oxide. We found that the band bending did not occur near the native oxide/BaSi{sub 2} interface. This result was clarified by the fact that the core-level emission peaks did not shift regardless of TOA (i.e., analysis depth). Thus, the barrier height of the native oxide for the minority-carriers in the undoped n-BaSi{sub 2} (holes) was determined to be 3.9 eV. No band bending in the BaSi{sub 2} close to the interface also suggests that the large minority-carrier lifetime in undoped n-BaSi{sub 2} films capped with native oxide is attributed not to the band bending in the BaSi{sub 2}, which pushes away photogenerated minority carriers from the defective surface region, but to the decrease of defective states by the native oxide.

  19. Investigation of the reaction of hydroxy and carbon monoxide to form hydrogen and carbon dioxide by Photoelectron-Photofragment Coincidence spectroscopy in a cryogenic ion beam trap

    Science.gov (United States)

    Johnson, Christopher Joseph

    2011-12-01

    The HOCO radical plays a crucial role in a wide variety of chemical processes, including atmospheric CO2 regulation and combustion chemistry, as an intermediate in the elementary reaction OH + CO → H + CO2 . However, scant information exists on this species due to the difficulties in studying it. Previous photoelectron-photofragment coincidence (PPC) studies performed in this laboratory have identified key processes occurring on the HOCO potential energy surface, but are complicated by the presence of internal excitation in the precursor anions, leading to uncertainties in product energies and dynamics. To address this, a new instrument has been constructed which incorporates a cryogenically cooled linear electrostatic storage device, providing a cold source of anions for dissociative photodetachment studies by PPC spectroscopy. The enhanced resolution and well-characterized energetics provided by this instrument have allowed the fundamental energetics and processes occurring on the HOCO potential energy surface to be studied in unprecedented detail. New data shows unambiguous confirmation of the presence of tunneling in the reaction HOCO → H + CO2. Careful study of this product channel has led to the generation a model one-dimensional potential barrier describing this process directly from experimental tunneling data, and tunneling lifetimes over a range of relevant internal energies to be predicted. High resolution photodetachment experiments provide a reassignment of the electron affinities of both cis- and trans-HOCO and the determination of several normal mode frequencies not previously measured in the gas phase, each with the support of high-level ab initio quantum chemical calculations. Further details on the previously-unknown isomer well depths and the process of isomerization have been extracted using this information. Finally, nonresonant two-photon photodetachment studies of NO2 -, a species with striking electronic structure similarities to HOCO

  20. Vibrational state-selective autodetachment photoelectron spectroscopy from dipole-bound states of cold 2-hydroxyphenoxide: o − HO(C{sub 6}H{sub 4})O{sup −}

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Dao-Ling; Wang, Lai-Sheng, E-mail: Lai-Sheng-Wang@brown.edu [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Liu, Hong-Tao [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Ning, Chuan-Gang [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China)

    2015-03-28

    We report a photodetachment and high-resolution photoelectron imaging study of cold 2-hydroxyphenoxide anion, o − HO(C{sub 6}H{sub 4})O{sup −}, cooled in a cryogenic ion trap. Photodetachment spectroscopy revealed a dipole-bound state (DBS) of the anion, 25 ± 5 cm{sup −1}, below the detachment threshold of 18784 ± 5 cm{sup −1} (2.3289 ± 0.0006 eV ), i.e., the electron affinity of the 2-hydroxyphenoxy radical o − HO(C{sub 6}H{sub 4})O{sup ⋅}. Twenty-two vibrational levels of the DBS are observed as resonances in the photodetachment spectrum. By tuning the detachment laser to these DBS vibrational levels, we obtain 22 high-resolution resonant photoelectron spectra, which are highly non-Franck-Condon due to mode-selective autodetachment and the Δv = − 1 propensity rule. Numerous Franck-Condon inactive vibrational modes are observed in the resonant photoelectron spectra, significantly expanding the vibrational information that is available in traditional high-resolution photoelectron spectroscopy. A total of 15 fundamental vibrational frequencies are obtained for the o − HO(C{sub 6}H{sub 4})O{sup ⋅}  radical from both the photodetachment spectrum and the resonant photoelectron spectra, including six symmetry-forbidden out-of-plane modes as a result of resonant enhancement.

  1. Electronic structure of nickel porphyrin NiP: Study by X-ray photoelectron and absorption spectroscopy

    Science.gov (United States)

    Svirskiy, G. I.; Sergeeva, N. N.; Krasnikov, S. A.; Vinogradov, N. A.; Sergeeva, Yu. N.; Cafolla, A. A.; Preobrajenski, A. B.; Vinogradov, A. S.

    2017-02-01

    Energy distributions and properties of the occupied and empty electronic states for a planar complex of nickel porphyrin NiP are studied by X-ray photoemission and absorption spectroscopy techniques. As a result of the analysis of the experimental spectra of valence photoemission, the nature and energy positions of the highest occupied electronic states were determined: the highest occupied state is formed mostly by atomic states of the porphine ligand; the following two states are associated with 3 d states of the nickel atom. It was found that the lowest empty state is specific and is described by the σ-type b 1 g MO formed by empty Ni3{d_{{x^2} - {y^2}}}-states and occupied 2 p-states of lone electron pairs of nitrogen atoms. This specific nature of the lowest empty state is a consequence of the donor-acceptor chemical bond in NiP.

  2. Photoelectron spectroscopy of self-assembled monolayers of molecular switches on noble metal surfaces; Photoelektronenspektroskopie selbstorganisierter Adsorbatschichten aus molekularen Schaltern auf Edelmetalloberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, Nils

    2012-09-12

    Self-assembled monolayers (SAMs) of butanethiolate (C4) on single crystalline Au(111) surfaces were prepared by adsorption from solution. The thermally activated desorption behaviour of the C4 molecules from the gold substrate was examined by qualitative thermal desorption measurements (TDM), through this a desorption temperature T{sub Des}=473 K could be determined. With this knowledge, it was possible to produce samples of very good surface quality, by thermal treatment T{sub Sample}spectroscopy of C4/Au was on the samples of the p x {radical}(3) phase using two-photon photoemission spectroscopy (2PPE). The spectra revealed clear signatures of two unoccupied resonance states at energies E-E{sub F}=3.7 eV and 3.9 eV. The low-energy state was assigned to the characteristic {sigma}*-resonance associated with the Au-S bond of the thiolate. The energy of the other resonance state agreed well with an interface state reported before for SAMs of an other alkanethiol on Au(111) in a densely packed phase. Furthermore the 2PPE data indicated that the high quality of the ex situ prepared SAMs supported the formation of image potential states. The reversible photo- and thermally activated isomerization of the molecular switch 3-(4-(4-Hexyl-phenylazo)-phenoxy)-propane-1-thiol (ABT), deposited by self-assembly from solution on Au(111), was examined using laser-based photoelectron spectroscopy. Differences in the molecular dipole moment characteristic for the trans and the cis isomer of ABT were observed via changes in the sample work function, accessible by detection of the threshold energy for photoemission. A quantitative

  3. Mechanism of anodic oxidation of molybdenum in nearly-neutral electrolytes studied by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Petrova, Manuela [University of Chemical Technology and Metallurgy, 8 Kl. Ohridski Blvd., 1756 Sofia (Bulgaria); Bojinov, Martin, E-mail: martin@uctm.edu [University of Chemical Technology and Metallurgy, 8 Kl. Ohridski Blvd., 1756 Sofia (Bulgaria); Zanna, Sandrine; Marcus, Philippe [Laboratoire de Physico-Chimie des Surfaces, CNRS-ENSCP (UMR7045), 11 Rue Pierre et Marie Curie, 75005 Paris (France)

    2011-09-30

    Anodic oxidation of molybdenum in weakly acidic, nearly neutral and weakly alkaline electrolytes was studied by voltammetric and electrochemical impedance spectroscopic measurements in a wide potential and pH range. Current vs. potential curves were found to exhibit two pseudo-Tafel regions suggesting two parallel pathways of the dissolution process. Electrochemical impedance spectra indicated the presence of at least two reaction intermediates. X-ray photoelectron spectroscopic (XPS) results pointed to the formation of an oxide containing Mo(IV), Mo(V) and Mo(VI), the exact ratio between different valence states depending on potential and pH of the solution. A physico-chemical model of the processes is proposed and a set of kinetic equations for the steady-state current vs. potential curve and the impedance response are derived. The model is found to reproduce quantitatively the current vs. potential curves and impedance spectra at a range of potentials and pH and to agree qualitatively with the XPS results. Subject to further improvement, the model could serve as a starting point for the optimization of the electrochemical fabrication of functional molybdenum oxide coatings.

  4. Two-photon finite-pulse model for resonant transitions in attosecond experiments

    CERN Document Server

    Galán, Álvaro Jiménez; Argenti, Luca

    2015-01-01

    We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate \\emph{ab initio} calculations, or be extracted from few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N=2 threshold for the RABITT (Reconstruction of Attosecond Beating by Interference of Two-photon Transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association to a weak IR probe, obtaining results in quantitative agreement with those from accurate \\emph{ab initio} simulations. In particular, we show that: i) Use of finite pulses results in a homogene...

  5. Photoelectron spectroscopy as an in situ contact-less method for studies of MOS properties of ultrathin oxides on Si

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Ana G., E-mail: acs@fct.unl.pt [CeFiTec, Department of Physics, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, P-2829-516 Caparica (Portugal); Pedersen, Kjeld [Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, DK-9220 Aalborg East (Denmark); Li, Zheshen S. [Institute for Storage Ring Facilities (ISA), Faculty of Science, Aarhus University, Ny Munkegade 120, Building 1520, DK-8000 Aarhus C (Denmark); Morgen, Per [Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark)

    2015-10-30

    Highlights: • Monitoring electric field changes within ultrathin oxides. • Contact-less method – no need for wires to the surface. • Probing of surface electronic levels through semi-open layer of metal particles. • Electron tunnelling through ultrathin oxide. - Abstract: The electric field across an ultrathin and uniform Si-oxide layer on a Si (1 1 1) surface and the positions of the valence band edges at the Si-oxide/Si (1 1 1) interface have been probed by high-resolution synchrotron radiation induced photoemission spectroscopy, as an in situ contact-less method. Variation of the “gate bias” is achieved by depositing Sn nanoparticles on the ultrathin oxide surface. These nanoparticles, growing as isolated hemi-spherical islands, attract various quantities of negative charges from the substrate inducing a potential difference between the Sn islands/Si-oxide and Si-oxide/Si (1 1 1) interface. This method allows us to study and extract the locally varying electric field and changes in the positions of the edges of the valence bands by measuring the valence band spectra and the Si 2p and Sn 4d core-levels at different Sn coverages. The ultrathin (0.8 nm thick) Si-oxide layer is grown in a simple and traceable self-limiting thermal process on a clean Si (1 1 1) surface. The oxide grown in this way creates flat bands. The properties of the system of Sn islands grown on this system are also determined. The induced electric field in the oxide varies linearly with the amount of Sn deposited per area.

  6. Benchmarking Attosecond Physics with Atomic Hydrogen

    Science.gov (United States)

    2015-05-25

    Final 3. DATES COVERED (From - To) 12 Mar 12 – 11 Mar 15 4. TITLE AND SUBTITLE Benchmarking attosecond physics with atomic hydrogen 5a...AND SUBTITLE Benchmarking attosecond physics with atomic hydrogen 5a. CONTRACT NUMBER FA2386-12-1-4025 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Final Report for AOARD Grant FA2386-12-1-4025 “ Benchmarking

  7. Attosecond nanoscale near-field sampling

    Science.gov (United States)

    Förg, B.; Schötz, J.; Süßmann, F.; Förster, M.; Krüger, M.; Ahn, B.; Okell, W. A.; Wintersperger, K.; Zherebtsov, S.; Guggenmos, A.; Pervak, V.; Kessel, A.; Trushin, S. A.; Azzeer, A. M.; Stockman, M. I.; Kim, D.; Krausz, F.; Hommelhoff, P.; Kling, M. F.

    2016-01-01

    The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. By comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted. PMID:27241851

  8. Vector potential photoelectron microscopy.

    Science.gov (United States)

    Browning, R

    2011-10-01

    A new class of electron microscope has been developed for the chemical microanalysis of a wide range of real world samples using photoelectron spectroscopy. Highly structured, three-dimensional samples, such as fiber mats and fracture surfaces can be imaged, as well as insulators and magnetic materials. The new microscope uses the vector potential field from a solenoid magnet as a spatial reference for imaging. A prototype instrument has demonstrated imaging of uncoated silk, magnetic steel wool, and micron-sized single strand tungsten wires.

  9. Photoelectron spectroscopy and theoretical study of M(IO3)2- (M = H, Li, Na, K): Structural evolution, optical isomers, and hyperhalogen behavior

    Science.gov (United States)

    Hou, Gao-Lei; Wu, Miao Miao; Wen, Hui; Sun, Qiang; Wang, Xue-Bin; Zheng, Wei-Jun

    2013-07-01

    H(IO3)2- and M(IO3)2- (M = Li, Na, K) anions were successfully produced via electrospray ionization of their corresponding bulk salt solutions, and were characterized by combining negative ion photoelectron spectroscopy and quantum chemical calculations. The experimental vertical detachment energies (VDEs) of M(IO3)2- (M = H, Li, Na, K) are 6.25, 6.57, 6.60, and 6.51 eV, respectively, and they are much higher than that of IO3- (4.77 eV). The theoretical calculations show that each of these anions has two energetically degenerate optical isomers. It is found that the structure of H(IO3)2- can be written as IO3-(HIO3), in which the H atom is tightly bound to one of the IO3- groups and forms an iodic acid (HIO3) molecule; while the structures of M(IO3)2- can be written as (IO3-)M+(IO3-), in which the alkali metal atoms interact with the two IO3- groups almost equally and bridge the two IO3- groups via two O atoms of each IO3- with the two MOOI planes nearly perpendicular to each other. In addition, the high VDEs of M(IO3)2- (M = Li, Na, K) can be explained by the hyperhalogen behavior of their neutral counterparts.

  10. Evolution of the SrTiO3/MoO3 interface electronic structure: An in situ photoelectron spectroscopy study

    KAUST Repository

    Du, Yuanmin

    2015-05-12

    Modifying the surface energetics, particularly the work function, of advanced materials is of critical importance for a wide range of surface- and interface-based devices. In this work, using in situ photoelectron spectroscopy, we investigated the evolution of electronic structure at the SrTiO3 surface during the growth of ultrathin MoO3 layers. Thanks to the large work function difference between SrTiO3 and MoO3, the energy band alignment on the SrTiO3 surface is significantly modified. The charge transfer and dipole formation at the SrTiO3/MoO3 interface leads to a large modulation of work function and an apparent doping in SrTiO3. The measured evolution of electronic structure and upward band bending suggest that the growth of ultrathin MoO3 layers is a powerful tool to modulate the surface energetics of SrTiO3, and this surface-engineering approach could be generalized to other functional oxides.

  11. Stark-assisted population control of coherent CS(2) 4f and 5p Rydberg wave packets studied by femtosecond time-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Knappenberger, Kenneth L; Lerch, Eliza-Beth W; Wen, Patrick; Leone, Stephen R

    2007-09-28

    A two-color (3+1(')) pump-probe scheme is employed to investigate Rydberg wave packet dynamics in carbon disulfide (CS(2) (*)). The state superpositions are created within the 4f and 5p Rydberg manifolds by three photons of the 400 nm pump pulse, and their temporal evolution is monitored with femtosecond time-resolved photoelectron spectroscopy using an 800 nm ionizing probe pulse. The coherent behavior of the non-stationary superpositions are observed through wavepacket revivals upon ionization to either the upper (12) or lower (32) spin-orbit components of CS(2) (+). The results show clearly that the composition of the wavepacket can be efficiently controlled by the power density of the excitation pulse over a range from 500 GWcm(2) to 10 TWcm(2). The results are consistent with the anticipated ac-Stark shift for 400 nm light and demonstrate an effective method for population control in molecular systems. Moreover, it is shown that Rydberg wavepackets can be formed in CS(2) with excitation power densities up to 10 TWcm(2) without significant fragmentation. The exponential 1e population decay (T(1)) of specific excited Rydberg states are recovered by analysis of the coherent part of the signal. The dissociation lifetimes of these states are typically 1.5 ps. However, a region exhibiting a more rapid decay ( approximately 800 fs) is observed for states residing in the energy range of 74 450-74 550 cm(-1), suggestive of an enhanced surface crossing in this region.

  12. Quantification of the toxic hexavalent chromium content in an organic matrix by X-ray photoelectron spectroscopy (XPS) and ultra-low-angle microtomy (ULAM)

    Science.gov (United States)

    Greunz, Theresia; Duchaczek, Hubert; Sagl, Raffaela; Duchoslav, Jiri; Steinberger, Roland; Strauß, Bernhard; Stifter, David

    2017-02-01

    Cr(VI) is known for its corrosion inhibitive properties and is, despite legal regulations, still a potential candidate to be added to thin (1-3 μm) protective coatings applied on, e.g., electrical steel as used for transformers, etc. However, Cr(VI) is harmful to the environment and to the human health. Hence, a reliable quantification of it is of decisive interest. Commonly, an alkaline extraction with a photometric endpoint detection of Cr(VI) is used for such material systems. However, this procedure requires an accurate knowledge on sample parameters such as dry film thickness and coating density that are occasionally associated with significant experimental errors. We present a comprehensive study of a coating system with a defined Cr(VI) pigment concentration applied on electrical steel. X-ray photoelectron spectroscopy (XPS) was employed to resolve the elemental chromium concentration and the chemical state. Turning to the fact that XPS is extremely surface sensitive (purpose a special sample preparation step performed on an ultra-microtome was required prior to analysis. Since a temperature increase leads to a reduction of Cr(VI) we extend our method on samples, which were subjected to different curing temperatures. We show that our proposed approach now allows to determine the elemental and Cr(VI) concentration and distribution inside the coating.

  13. Chemical state analysis of trace-level alkali metals sorbed in micaceous oxide by total reflection X-ray photoelectron spectroscopy

    Science.gov (United States)

    Baba, Y.; Shimoyama, I.; Hirao, N.

    2016-10-01

    In order to determine the chemical states of radioactive cesium (137Cs or 134Cs) sorbed in clay minerals, chemical states of cesium as well as the other alkali metals (sodium and rubidium) sorbed in micaceous oxides have been investigated by X-ray photoelectron spectroscopy (XPS). Since the number of atoms in radioactive cesium is extremely small, we specially focused on chemical states of trace-level alkali metals. For this purpose, we have measured XPS under X-ray total reflection (TR) condition. For cesium, it was shown that ultra-trace amount of cesium down to about 100 pg cm-2 can be detected by TR-XPS. This amount corresponds to about 200 Bq of 137Cs (t1/2 = 30.2 y). It was demonstrated that ultra-trace amount of cesium corresponding to radioactive cesium level can be measured by TR-XPS. As to the chemical states, it was found that core-level binding energy in TR-XPS for trace-level cesium shifted to lower-energy side compared with that for thicker layer. A reverse tendency is observed in sodium. Based on charge transfer within a simple point-charge model, it is concluded that chemical bond between alkali metal and micaceous oxide for ultra-thin layer is more polarized that for thick layer.

  14. Corrosive effects of fluoride on titanium: investigation by X-ray photoelectron spectroscopy, atomic force microscopy, and human epithelial cell culturing.

    Science.gov (United States)

    Stájer, Anette; Ungvári, Krisztina; Pelsoczi, István K; Polyánka, Hilda; Oszkó, Albert; Mihalik, Erzsébet; Rakonczay, Zoltán; Radnai, Márta; Kemény, Lajos; Fazekas, András; Turzó, Kinga

    2008-11-01

    High fluoride (F(-)) concentrations and acidic pH impair the corrosion resistance of titanium (Ti). Effects of F(-)-containing caries-preventive prophylactic rinses, and gels on Ti were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Human epithelial cell attachment and proliferation were investigated by dimethylthiazol-diphenyl tetrazolium bromide (MTT) and protein content assays. Aqueous 1% NaF solution (3800 ppm F(-), pH 4.5) or high (12,500 ppm) F(-) content gel (pH 4.8) strongly corroded the surface and modified its composition. XPS revealed formation of a strongly bound F(-)-containing complex (Na(2)TiF(6)). AFM indicated an increase in roughness (R(a)) of the surfaces: 10-fold for the NaF solution and smaller for the gel or a mouthwash (250 ppm F(-), pH 4.4). MTT revealed that cell attachment was significantly increased by the gel, but was not disturbed by either the mouthwash or the NaF. Cell proliferation determined by MTT decreased significantly only for the NaF-treated samples; protein content assay experiments showed no such effect. This study indicates that epithelial cell culturing results can depend on the method used, and the adverse effects of a high F(-) concentration and low pH should be considered when prophylactic gels are applied by patients with Ti implants or other dental devices.

  15. Recycling of CO2: Probing the Chemical State of the Ni(111) Surface during the Methanation Reaction with Ambient-Pressure X-Ray Photoelectron Spectroscopy.

    Science.gov (United States)

    Heine, Christian; Lechner, Barbara A J; Bluhm, Hendrik; Salmeron, Miquel

    2016-10-12

    Using ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), we studied the adsorption and reactions of CO2 and CO2 + H2 on the Ni(111) surface to identify the surface chemical state and the nature of the adsorbed species during the methanation reaction. In 200 mTorr CO2, we found that NiO is formed from CO2 dissociation into CO and atomic oxygen. Additionally, carbonate (CO3(2-)) is present on the surface from further reaction of CO2 with NiO. The addition of H2 into the reaction environment leads to reduction of NiO and the disappearance of CO3(2-). At temperatures >160 °C, CO adsorbed on hollow sites, and atomic carbon and OH species are present on the surface. We conclude that the methanation reaction proceeds via dissociation of CO2, followed by reduction of CO to atomic carbon and its hydrogenation to methane.

  16. Hard X-ray photoelectron spectroscopy of Li{sub x}Ni{sub 1−x}O epitaxial thin films with a high lithium content

    Energy Technology Data Exchange (ETDEWEB)

    Kumara, L. S. R., E-mail: KUMARA.Rosantha@nims.go.jp; Yang, Anli [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), 1-1-1 Kouto, Sayo, Hyogo 679-5148 (Japan); Sakata, Osami, E-mail: SAKATA.Osami@nims.go.jp [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), 1-1-1 Kouto, Sayo, Hyogo 679-5148 (Japan); Synchrotron X-ray Group, Quantum Beam Unit, NIMS, 1-1-1 Kouto, Sayo, Hyogo 679-5148 (Japan); Department of Innovative and Engineered Materials, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259-J3-16, Nagatsuta, Midori, Yokohama 226-8502 (Japan); Yamauchi, Ryosuke; Matsuda, Akifumi; Yoshimoto, Mamoru [Department of Innovative and Engineered Materials, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259-J3-16, Nagatsuta, Midori, Yokohama 226-8502 (Japan); Taguchi, Munetaka [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Ikoma, Nara 630-0192 (Japan)

    2014-07-28

    The core-level and valence-band electronic structures of Li{sub x}Ni{sub 1−x}O epitaxial thin films with x = 0, 0.27, and 0.48 were studied by hard X-ray photoelectron spectroscopy. A double peak structure, consisting of a main peak and a shoulder peak, and a satellite structure were observed in the Ni 2p{sub 3/2} core-level spectra. The intensity ratio of the shoulder to main peak in this double peak structure increased with increasing lithium content in Li{sub x}Ni{sub 1−x}O. This lithium doping dependence of the Ni 2p{sub 3/2} core-level spectra was investigated using an extended cluster model, which included the Zhang–Rice (ZR) doublet bound states arising from a competition between O 2p – Ni 3d hybridization and the Ni on-site Coulomb interaction. The results indicated that the change in the intensity ratio in the main peak is because of a reduction in the ZR doublet bound states from lithium substitutions. This strongly suggests that holes compensating Li doping in Li{sub x}Ni{sub 1−x}O are of primarily ZR character.

  17. Photoelectron spectroscopy investigation of the temperature-induced deprotonation and substrate-mediated hydrogen transfer in a hydroxyphenyl-substituted porphyrin

    CERN Document Server

    Smykalla, Lars; Mende, Carola; Lang, Heinrich; Knupfer, Martin; Hietschold, Michael

    2015-01-01

    The temperature dependent stepwise deprotonation of 5,10,15,20-tetra(p-hydroxyphenyl)porphyrin is investigated using photoelectron spectroscopy. An abundance of pyrrolic relative to iminic nitrogen and a decrease in the ratio of the amount of -NH- to -N= with increasing annealing temperature is found. In contrast to the molecules adsorbed on Au(111), on the more reactive Ag(110) surface, partial dissociation of the hydroxyl groups and subsequent diffusion and rebonding of hydrogen to the central nitrogen atoms resulting in a zwitterionic molecule was clearly observed. Moreover, partial C-H bond cleavage and the formation of new covalent bonds with adjacent molecules or the surface starts at a relatively high annealing temperature of 300{\\deg}C. This reaction is identified to occur at the carbon atoms of the pyrrole rings, which leads also to a shift in the N 1s signal and changes in the valence band of the molecules. Our results show that annealing can significantly alter the molecules which were deposited de...

  18. Electronic and geometric properties of Au nanoparticles on Highly Ordered Pyrolytic Graphite (HOPG) studied using X-ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM).

    Science.gov (United States)

    Lopez-Salido, Ignacio; Lim, Dong Chan; Dietsche, Rainer; Bertram, Nils; Kim, Young Dok

    2006-01-26

    Au nanoparticles grown on mildly sputtered Highly Ordered Pyrolytic Graphite (HOPG) surfaces were studied using Scanning Tunneling Microscopy (STM) and X-ray Photoelectron Spectroscopy (XPS). The results were compared with those of Ag nanoparticles on the same substrate. By varying the defect densities of HOPG and the Au coverages, one can create Au nanoparticles in various sizes. At high Au coverages, the structures of the Au films significantly deviate from the ideal truncated octahedral form: the existence of many steps between different Au atomic layers can be observed, most likely due to a high activation barrier of the diffusion of Au atoms across the step edges. This implies that the particle growth at room temperature is strongly limited by kinetic factors. Hexagonal shapes of Au structures could be identified, indicating preferential growth of Au nanostructures along the (111) direction normal to the surface. In the case of Au, XPS studies reveal a weaker core level shift with decreasing particle size compared to the 3d level in similarly sized Ag particles. Also taking into account the Auger analysis of the Ag particles, the core level shifts of the metal nanoparticles on HOPG can be understood in terms of the metal/substrate charge transfer. Ag is (partially) positively charged, whereas Au negatively charged on HOPG. It is demonstrated that XPS can be a useful tool to study metal-support interactions, which plays an important role for heterogeneous catalysis, for example.

  19. Optical and X-ray photoelectron spectroscopy of PbGeO3 and Pb5Ge3O11 single crystals

    Indian Academy of Sciences (India)

    S C Sabharwal; S N Jha; Sangeeta

    2010-08-01

    Pb5Ge3O11 crystals are found to exhibit pale yellow colouration while PbGeO3 are colourless. X-ray photoelectron spectroscopy (XPS) measurements show lead deficiency in both the crystals. The results also reveal a stronger ionic character for PbGeO3 as compared to Pb5Ge3O11 crystal. The binding energy of Ge3 core level in the case of Pb5Ge3O11 crystal is found to be smaller than the binding energy of germanium oxide, thereby indicating the incomplete oxidation of Ge ions in the crystal lattice. On gamma ray irradiation, the transmission of both the crystals is observed to deteriorate uniformly over the entire wavelength range, which has been attributed to the oxidation of some of the lattice Pb ions. On gamma irradiation the changes observed in O1 core level energies for both the crystals are seen to be consistent with the changes noted in the Pb47/2 and Ge3 spectra. Interestingly, the results reveal oxidation of surface Ge atoms with atmospheric oxygen under gamma irradiation.

  20. Electronic structure and correlation in β -T i3O5 and λ -T i3O5 studied by hard x-ray photoelectron spectroscopy

    Science.gov (United States)

    Kobayashi, Keisuke; Taguchi, Munetaka; Kobata, Masaaki; Tanaka, Kenji; Tokoro, Hiroko; Daimon, Hiroshi; Okane, Tetsuo; Yamagami, Hiroshi; Ikenaga, Eiji; Ohkoshi, Shin-ichi

    2017-02-01

    We have conducted hard x-ray photoelectron spectroscopy investigations of the electronic structure changes and electron correlation phenomena which take place upon the photoinduced reversible phase transition between β- and λ -T i3O . From valence band spectra of β- and λ -T i3O5 , we have identified the bipolaron caused by the σ-type bonding of dx y orbitals in β -T i3O5 and the π stacking between the dx y orbitals between different Ti sites in λ -T i3O5 , previously predicted by ab initio calculations. This indicates that the single electron band picture is valid for the description of photoinduced phase transitions. On the other hand, the Ti 2 p and Ti 1 s core level spectra exhibit nonlocal screening satellite features, which are typical spectroscopic signs of strong electron correlation in the coherent Ti t2 g states. The most striking result we obtain is that correlation in the valence band also manifests to reduce the plasmon energy, which results in an enhancement of the valence electron mass by a factor of 2.7.

  1. Cu in In{sub 2}S{sub 3}: interdiffusion phenomena analysed by high kinetic energy X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pistor, P.; Allsop, N.; Caballero, R.; Camus, C.; Grimm, A.; Johnson, B.; Kropp, T.; Lauermann, I.; Lehmann, S.; Schorr, S.; Weber, A.; Klenk, R. [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH (HZB), Berlin (Germany); Braun, W.; Gorgoi, M. [Berliner Elektronenspeicherring-Gesellschaft fuer Synchrotronstrahlung m.b.H., Berlin (Germany); Fischer, Ch.-H. [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH (HZB), Berlin (Germany); Freie Universitaet Berlin (Germany). Fachbereich Physik; Moenig, H. [Freie Universitaet Berlin (Germany). Fachbereich Physik

    2009-05-15

    Chalcopyrite thin film solar cells with an In{sub 2}S{sub 3} buffer showed high efficiencies above 15%, but only after annealing at 200 C. One possible explanation is a Cu interdiffusion at the absorber/buffer interface. We were able to directly measure a Cu interdiffusion with a new tool at the BESSY synchrotron facility: HIKE (high kinetic energy X-ray photoelectron spectroscopy). Due to its increased information depth of up to 10-20 nm HIKE is able to provide chemical information even through thin closed overlayers. The HIKE endstation also allows in-situ heating. A layer stack of In{sub 2}S{sub 3}/ Cu(In,Ga)Se{sub 2} was prepared and heated in-situ up to a temperature of 300 C while continuously measuring HIKE spectra. A strong increase of the Cu signal above temperatures around 200 C was found. With this setup we were able to directly monitor the Cu diffusion from the absorber into the buffer layer. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Influence of surface hydroxylation on 3-aminopropyltriethoxysilane growth mode during chemical functionalization of GaN Surfaces: an angle-resolved X-ray photoelectron spectroscopy Study.

    Science.gov (United States)

    Arranz, A; Palacio, C; García-Fresnadillo, D; Orellana, G; Navarro, A; Muñoz, E

    2008-08-19

    A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown on sapphire substrates by metal-organic chemical vapor deposition was carried out. Both types of samples were chemically functionalized with 3-aminopropyltriethoxysilane (APTES) using a well-established silane-based approach for functionalizing hydroxylated surfaces. The untreated surfaces as well as those modified by hydroxylation and APTES deposition were analyzed using angle-resolved X-ray photoelectron spectroscopy. Strong differences were found between the APTES growth modes on n- and p-GaN surfaces that can be associated with the number of available hydroxyl groups on the GaN surface of each sample. Depending on the density of surface hydroxyl groups, different mechanisms of APTES attachment to the GaN surface take place in such a way that the APTES growth mode changes from a monolayer to a multilayer growth mode when the number of surface hydroxyl groups is decreased. Specifically, a monolayer growth mode with a surface coverage of approximately 78% was found on p-GaN, whereas the formation of a dense film, approximately 3 monolayers thick, was observed on n-GaN.

  3. In situ SERS and X-ray photoelectron spectroscopy studies on the pH-dependant adsorption of anthraquinone-2-carboxylic acid on silver electrode

    Science.gov (United States)

    Li, Dan; Jia, Shaojie; Fodjo, Essy Kouadio; Xu, Hu; Wang, Yuhong; Deng, Wei

    2016-03-01

    In this study, in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) are used to investigate the redox reaction and adsorption behavior of anthraquinone-2-carboxylic acid (AQ-2-COOH) on an Ag electrode at different pH values. The obtained results indicate that AQ-2-COOH is adsorbed tilted on the Ag electrode through O-atom of ring carbonyl in a potential range from -0.3 to -0.5 V vs. SCE, but the orientation turns to more tilted orientation with both O-atom of the ring carbonyl and carboxylate group in positive potential region for pH 6.0 and 7.4. However, at pH 10.0, the orientation adopts tilted conformation constantly on the Ag electrode with both O-atom of the anthraquinone ring and carboxylate group in the potential range from -0.3 to -0.5 V vs. SCE or at positive potentials. Moreover, the adsorption behavior of AQ-2-COOH has been further confirmed by AR-XPS on the Ag surface. Proposed reasons for the observed changes in orientation are presented.

  4. Chemical interaction at the buried silicon/zinc oxide thin-film solar cell interface as revealed by hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wimmer, M., E-mail: mark.wimmer@helmholtz-berlin.de [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Gerlach, D.; Wilks, R.G.; Scherf, S.; Félix, R. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Lupulescu, C. [Institute for Optics and Atomic Physics, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Ruske, F.; Schondelmaier, G.; Lips, K. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Hüpkes, J. [Institute for Energy Research, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Gorgoi, M. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Eberhardt, W. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Institute for Optics and Atomic Physics, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Rech, B. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Bär, M., E-mail: marcus.baer@helmholtz-berlin.de [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Institut für Physik und Chemie, Brandenburgische Technische Universität Cottbus, Konrad-Wachsmann-Allee 1, 03046 Cottbus (Germany)

    2013-10-15

    Highlights: •We used HAXPES to identify chemical interactions at the buried silicon/aluminum-doped zinc oxide thin-film solar cell interface. •The results indicate a diffusion of zinc and aluminum into the silicon upon annealing procedures which are part of the solar cell processing. •The contamination of the silicon may be detrimental for the solar cell performance. -- Abstract: Hard X-ray photoelectron spectroscopy (HAXPES) is used to identify chemical interactions (such as elemental redistribution) at the buried silicon/aluminum-doped zinc oxide thin-film solar cell interface. Expanding our study of the interfacial oxidation of silicon upon its solid-phase crystallization (SPC), in which we found zinc oxide to be the source of oxygen, in this investigation we address chemical interaction processes involving zinc and aluminum. In particular, we observe an increase of zinc- and aluminum-related HAXPES signals after SPC of the deposited amorphous silicon thin films. Quantitative analysis suggests an elemental redistribution in the proximity of the silicon/aluminum-doped zinc oxide interface – more pronounced for aluminum than for zinc – as explanation. Based on these insights the complex chemical interface structure is discussed.

  5. A study of the O/Ag(111) system with scanning tunneling microscopy and x-ray photoelectron spectroscopy at ambient pressures

    Science.gov (United States)

    Heine, Christian; Eren, Baran; Lechner, Barbara A. J.; Salmeron, Miquel

    2016-10-01

    The interaction of O2 with the Ag(111) surface was studied with scanning tunneling microscopy (STM) in the pressure range from 10- 9 Torr to 1 atm at room temperature and with X-ray photoelectron spectroscopy (XPS) up to 0.3 Torr O2 in the temperature range from RT to 413 K. STM images show that the Ag(111) surface topography is little affected in regions with large flat terraces, except for the appearance of mobile features due to oxygen atoms at pressures above 0.01 Torr. In regions where the step density is high, the surface became rough under 0.01 Torr of O2, due to the local oxidation of Ag. Various chemical states of oxygen due to chemisorbed, oxide and subsurface species were identified by XPS as a function of pressure and temperature. The findings from the STM images and XPS measurements indicate that formation of an oxide phase, the thermodynamically stable form at room temperature under ambient O2 pressure, is kinetically hindered in the flat terrace areas but proceeds readily in regions with high-step density.

  6. Understanding the Adsorption of CuPc and ZnPc on Noble Metal Surfaces by Combining Quantum-Mechanical Modelling and Photoelectron Spectroscopy

    Directory of Open Access Journals (Sweden)

    Yu Li Huang

    2014-03-01

    Full Text Available Phthalocyanines are an important class of organic semiconductors and, thus, their interfaces with metals are both of fundamental and practical relevance. In the present contribution we provide a combined theoretical and experimental study, in which we show that state-of-the-art quantum-mechanical simulations are nowadays capable of treating most properties of such interfaces in a quantitatively reliable manner. This is shown for Cu-phthalocyanine (CuPc and Zn-phthalocyanine (ZnPc on Au(111 and Ag(111 surfaces. Using a recently developed approach for efficiently treating van der Waals (vdW interactions at metal/organic interfaces, we calculate adsorption geometries in excellent agreement with experiments. With these geometries available, we are then able to accurately describe the interfacial electronic structure arising from molecular adsorption. We find that bonding is dominated by vdW forces for all studied interfaces. Concomitantly, charge rearrangements on Au(111 are exclusively due to Pauli pushback. On Ag(111, we additionally observe charge transfer from the metal to one of the spin-channels associated with the lowest unoccupied π-states of the molecules. Comparing the interfacial density of states with our ultraviolet photoelectron spectroscopy (UPS experiments, we find that the use of a hybrid functionals is necessary to obtain the correct order of the electronic states.

  7. In situ investigations of laser and thermally modified As{sub 2}S{sub 3} nanolayers: Synchrotron radiation photoelectron spectroscopy and density functional theory calculations

    Energy Technology Data Exchange (ETDEWEB)

    Kondrat, O., E-mail: o.b.kondrat@gmail.com; Holomb, R.; Popovich, N.; Mitsa, V. [Institute of Solid State Physics and Chemistry, Uzhhorod National University, Pidhirna Str., 46, 88000 Uzhhorod (Ukraine); Veres, M. [Wigner Research Centre for Physics, Hungarian Academy of Sciences, 1121 Budapest (Hungary); Csik, A. [Institute for Nuclear Research, Hungarian Academy of Sciences, H-4001 Debrecen (Hungary); Feher, A. [Pavol Jozef Šafárik University in Košice, Park Angelinum 9, Košice (Slovakia); Tsud, N.; Matolín, V. [Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Prague 8 (Czech Republic); Vondráček, M. [Institute of Physics, Academy of Science of the Czech Republic, Na Slovance 2, CZ-182 21 Prague 8 (Czech Republic); Prince, K. C. [Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, in Area Science Park, 34149 Basovizza, Trieste (Italy); Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, 34149 Basovizza, Trieste (Italy)

    2015-12-14

    As-deposited, annealed, and in situ As{sub 2}S{sub 3} nanolayers, illuminated by blue (405 nm) and red (650 nm) laser light, were studied using synchrotron radiation photoelectron spectroscopy and DFT electronic structure calculations. Changes in composition and local atomic coordination occurring in the irradiated region of As{sub 2}S{sub 3} films were monitored by analysis of As 3d and S 2p core levels. These studies show that both the thermal treatment and the red laser illumination of As{sub 2}S{sub 3} nanolayers decrease the concentration of homopolar (As-As and S-S) bonds. From the other hand, an increasing concentration of As-rich structural units (s.u.) with a homopolar As-As bond was observed under in situ blue laser illumination of As{sub 2}S{sub 3} nanolayers. Molecular orbital energies were calculated for different As- and S-centered s.u. and used for the interpretation of the core levels and valence band spectra. The surface local structure of the As{sub 2}S{sub 3} nanolayers and its photoinduced transformation are discussed in detail.

  8. New insight brought by density functional theory on the chemical state of alaninol on Cu(100): Energetics and interpretation of x-ray photoelectron spectroscopy data

    Science.gov (United States)

    Irrera, S.; Costa, D.

    2008-03-01

    In recent years, an increasing interest has been focused on the adsorption of molecules on surfaces due to the importance of technologies based on the interaction of organic systems with metals and oxides for biosensors, catalysis, and molecularly imprinted polymer technology. A particularly attractive area is the study of chiral surfaces, as these can act as heterogeneous catalysts and sensors in the stereochemical industrial processes. This work reports on an ab initio simulation of chemisorption of the D-alaninol on Cu (100). This system has been investigated systematically by using the Vienna ab initio simulation Package (VASP) which performs density functional theory (DFT) calculations in periodic boundary conditions. Molecular dynamics at 300K is performed to explore all the possible geometries, finally, optimized at 0K to obtain the adsorption modes. C 1s, O 1s, and N 1s, core level shift (CLS) calculations of those adsorption modes have been evaluated and compared with x-ray photoelectron spectroscopy experimental data. Energetic and CLS indicate that both chemical functions, the NH2 and the dehydrogenated hydroxyl, are involved in the bonding to the surface at low coverage. Atomic hydrogen coadsorbs in a fourfold hollow site. An atomistic thermodynamics approach suggests that at room temperature under UHV conditions, coadsorbed hydrogen has recombined as H2 and desorbed from the surface.

  9. Multimode Surface Functional Group Determination: Combining Steady-State and Time-Resolved Fluorescence with X-ray Photoelectron Spectroscopy and Absorption Measurements for Absolute Quantification.

    Science.gov (United States)

    Fischer, Tobias; Dietrich, Paul M; Unger, Wolfgang E S; Rurack, Knut

    2016-01-19

    The quantitative determination of surface functional groups is approached in a straightforward laboratory-based method with high reliability. The application of a multimode BODIPY-type fluorescence, photometry, and X-ray photoelectron spectroscopy (XPS) label allows estimation of the labeling ratio, i.e., the ratio of functional groups carrying a label after reaction, from the elemental ratios of nitrogen and fluorine. The amount of label on the surface is quantified with UV/vis spectrophotometry based on the molar absorption coefficient as molecular property. The investigated surfaces with varying density are prepared by codeposition of 3-(aminopropyl)triethoxysilane (APTES) and cyanoethyltriethoxysilane (CETES) from vapor. These surfaces show high functional group densities that result in significant fluorescence quenching of surface-bound labels. Since alternative quantification of the label on the surface is available through XPS and photometry, a novel method to quantitatively account for fluorescence quenching based on fluorescence lifetime (τ) measurements is shown. Due to the complex distribution of τ on high-density surfaces, the stretched exponential (or Kohlrausch) function is required to determine representative mean lifetimes. The approach is extended to a commercial Rhodamine B isothiocyanate (RITC) label, clearly revealing the problems that arise from such charged labels used in conjunction with silane surfaces.

  10. An X-ray photoelectron spectroscopy study of the products of the interaction of gaseous IrF6 with fine UO2F2

    Directory of Open Access Journals (Sweden)

    Prusakov Vladimir N.

    2007-01-01

    Full Text Available Nuclear fuel reprocessing by fluorination, a dry method of regeneration of spent nuclear fuel, uses UO2F2 for the separation of plutonium from gaseous mixtures. Since plutonium requires special treatment, IrF6 was used as a thermodynamic model of PuF6. The model reaction of the interaction of gaseous IrF6 with fine UO2F2 in the sorption column revealed a change of color of the sorption column contents from pale-yellow to gray and black, indicating the formation of products of such an interaction. The X-ray photoelectron spectroscopy study showed that the interaction of gaseous IrF6 with fine UO2F2 at 125 °C results in the formation of stable iridium compounds where the iridium oxidation state is close to Ir3+. The dependence of the elemental compositions of the layers in the sorption column on the penetration depth of IrF6 was established.

  11. In Situ Observation of Water Dissociation with Lattice Incorporation at FeO Particle Edges Using Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Xingyi [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Lee, Junseok [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Wang, Congjun [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Matranga, Christopher [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Aksoy, Funda [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nigde University, Nigde (Turkey). Dept. of Physics; Liu, Zhi [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2011-03-15

    The dissociation of H2O and formation of adsorbed hydroxyl groups, on FeO particles grown on Au(111) were identified with in situ,: X:ray photoelectron spectroscopy (XPS) at water pressures ranging from 3 x 10-8 to 0.1 Torr. The facile dissociation of H2O takes place at FeO particle edges, and it was successfully observed in situ With atomically resolved scanning tunneling microscopy (STM). The in situ STM studies show that adsorbed hydroxyl groups were formed exclusively along the edges of the FeO particles with the 0 atom becoming directly incorporated into the oxide crystalline lattice The STM results are consistent with coordinatively unsaturated ferrous (CUF) sites along the FeO particle edge causing the observed reactivity with H2O. Our results also directly illustrate how structural defects and under.-coordinated sites participate in chemical reactions.

  12. Acid-base interactions in amorphous solid dispersions of lumefantrine prepared by spray-drying and hot-melt extrusion using X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Song, Yang; Zemlyanov, Dmitry; Chen, Xin; Su, Ziyang; Nie, Haichen; Lubach, Joseph W; Smith, Daniel; Byrn, Stephen; Pinal, Rodolfo

    2016-12-05

    This study investigates drug-excipient interactions in amorphous solid dispersions (ASDs) of the model basic compound lumefantrine (LMN), with five acidic polymers. X-ray photoelectron spectroscopy (XPS) was used to measure the extent of the protonation of the tertiary amine in LMN by the five acidic polymers. The extent/efficiency of protonation of the ASDs was assessed a function of polymer type, manufacturing process (hot-melt extrusion vs. spray drying), and drug loading (DL). The most strongly acidic polymer, polystyrene sulfonic acid (PSSA) was found to be the most efficient polymer in protonating LMN, independently of manufacturing method and DL. The rank order for the protonation extent of LMN by each polymer is roughtly the same for both manufacturing processes. However, protonation efficiency of polymers of similar acidic strength ranged from ∼0% to 75% (HPMCAS and Eudragit L100-55, respectively), suggesting an important role of molecular/mixing effects. For some polymers, including Eudragit L100 55 and HPMCP, spray-drying resulted in higher protonation efficiency compared to hot-melt extrusion. This result is attributable to a more favorable encounter between acid and base groups, when exposed to each other in solution phase. Increasing DL led to decreased protonation efficiency in most cases, particularly for polyacrylic acid, despite having the highest content of acidic groups per unit mass. These results indicate that the combined effects of acid strength and mixing phenomena regulate the efficiency of acid-base interactions in the ASDs.

  13. sp2/sp3 hybridization ratio in amorphous carbon from C 1s core-level shifts: X-ray photoelectron spectroscopy and first-principles calculation

    Science.gov (United States)

    Haerle, Rainer; Riedo, Elisa; Pasquarello, Alfredo; Baldereschi, Alfonso

    2002-01-01

    Using a combined experimental and theoretical approach, we address C 1s core-level shifts in amorphous carbon. Experimental results are obtained by x-ray photoelectron spectroscopy (XPS) and electron-energy-loss spectroscopy (EELS) on thin-film samples of different atomic density, obtained by a pulsed-laser deposition growth process. The XPS spectra are deconvoluted into two contributions, which are attributed to sp2- and sp3-hybridized atoms, respectively, separated by 0.9 eV, independent of atomic density. The sp3 hybridization content extracted from XPS is consistent with the atomic density derived from the plasmon energy in the EELS spectrum. In our theoretical study, we generate several periodic model structures of amorphous carbon of different densities applying two schemes of increasing accuracy in sequence. We first use a molecular-dynamics approach, based on an environmental-dependent tight-binding Hamiltonian to quench the systems from the liquid phase. The final model structures are then obtained by further atomic relaxation using a first-principles pseudopotential plane-wave approach within density-functional theory. Within the latter framework, we also calculate carbon 1s core-level shifts for our disordered model structures. We find that the shifts associated to threefold- and fourfold- coordinated carbon atoms give rise to two distinct peaks separated by about 1.0 eV, independent of density, in close agreement with experimental observations. This provides strong support for decomposing the XPS spectra into two peaks resulting from sp2- and sp3-hybridized atoms. Core-hole relaxations effects account for about 30% of the calculated shifts.

  14. Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources.

    Science.gov (United States)

    Shavorskiy, Andrey; Neppl, Stefan; Slaughter, Daniel S; Cryan, James P; Siefermann, Katrin R; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P; Zegkinoglou, Ioannis; Fraund, Matthew W; Khurmi, Champak; Hertlein, Marcus P; Wright, Travis W; Huse, Nils; Schoenlein, Robert W; Tyliszczak, Tolek; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A; Rude, Bruce S; Ölsner, Andreas; Mähl, Sven; Bluhm, Hendrik; Gessner, Oliver

    2014-09-01

    An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ~9 ns at a pass energy of 50 eV and ~1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with

  15. The method of the photoelectron spectroscopy for the observation of ultrafst processes in metals; Die Methode der Photoelektronenspektroskopie zur Beobachtung ultraschneller Prozesse in Metallen

    Energy Technology Data Exchange (ETDEWEB)

    Heinz, Oliver

    2007-12-15

    An essential thematic main topic of this experimental-physical thesis is the observation of the thermalization of hot electrons of a metal film, which were excited and heated by an ultrashort laser pulse. Applied for this was a modification of the method of the photoelectron spectroscopy, at which it is by an optical-pump examination technique possible, to study the dynamics of the electron energy distribution in the metal with high time resolution. The laser pulses required for the surpassing of the metal escape work in the ultraviolet spectral range are by that produced, that pulses of a Ti:sapphire laser system in the infrared spectral region and a pulse duration of 40 femtoseconds are frequency-multiplied. For the success of this measurement method with high time resolution high requirements both on the quality of the exciting laser pulses and the ultrahigh-vacuum apparature of the photoelectron spectrometer are indispensable. The essential details of these special requirements are extensively discussed in this thesis. The excitation of the metal sample by intense and ultrashort laser pulses of different wavelength led after evaluation of the photoemission spectra and after analysis of the structural character of the metal surface to an extension of already existing knowledge concerning the photoemission at simultaneous absorption of two or several photons. [German] Ein wesentlicher thematischer Schwerpunkt dieser experimentalphysikalischen Arbeit ist die Beobachtung der Thermalisierung heisser Elektronen eines Metallfilms, welche mit einem ultrakurzen Laserimpuls angeregt und aufgeheizt wurden. Verwendet wurde dazu eine Abwandlung der Methode der Photoelektronenspektroskopie, bei der es durch eine optische Pump-Abfrage-Technik moeglich ist, die Dynamik der Elektronenenergieverteilung im Metall mit hoher Zeitaufloesung zu untersuchen. Die zur Ueberwindung der metallischen Austrittsarbeit erforderlichen Laserimpulse im ultravioletten Spektralbereich werden

  16. Photoelectron circular dichroism of isopropanolamine

    Science.gov (United States)

    Catone, D.; Turchini, S.; Contini, G.; Prosperi, T.; Stener, M.; Decleva, P.; Zema, N.

    2017-01-01

    Spectroscopies based on circular polarized light are sensitive to the electronic and structural properties of chiral molecules. Photoelectron circular dichroism (PECD) is a powerful technique that combines the chiral sensitivity of the circular polarized light and the electronic information obtained by photoelectron spectroscopy. An experimental and theoretical PECD study of the outer valence and C 1s core states of 1-amino-2-propanol in the gas phase is presented. The experimental dichroic dispersions in the photoelectron kinetic energy are compared with theoretical calculations employing a multicentric basis set of B-spline functions and a Kohn-Sham Hamiltonian. In order to understand analogies and differences in the dichroism of structural isomers bearing the same functional groups, a comparison with previous PECD study of valence band of 2-amino-1-propanol is carried out.

  17. Theory of attosecond delays in molecular photoionization

    Science.gov (United States)

    Baykusheva, Denitsa; Wörner, Hans Jakob

    2017-03-01

    We present a theoretical formalism for the calculation of attosecond delays in molecular photoionization. It is shown how delays relevant to one-photon-ionization, also known as Eisenbud-Wigner-Smith delays, can be obtained from the complex dipole matrix elements provided by molecular quantum scattering theory. These results are used to derive formulae for the delays measured by two-photon attosecond interferometry based on an attosecond pulse train and a dressing femtosecond infrared pulse. These effective delays are first expressed in the molecular frame where maximal information about the molecular photoionization dynamics is available. The effects of averaging over the emission direction of the electron and the molecular orientation are introduced analytically. We illustrate this general formalism for the case of two polyatomic molecules. N2O serves as an example of a polar linear molecule characterized by complex photoionization dynamics resulting from the presence of molecular shape resonances. H2O illustrates the case of a non-linear molecule with comparably simple photoionization dynamics resulting from a flat continuum. Our theory establishes the foundation for interpreting measurements of the photoionization dynamics of all molecules by attosecond metrology.

  18. Photoelectronic characterization of heterointerfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Brumbach, Michael Todd

    2012-02-01

    In many devices such as solar cells, light emitting diodes, transistors, etc., the performance relies on the electronic structure at interfaces between materials within the device. The objective of this work was to perform robust characterization of hybrid (organic/inorganic) interfaces by tailoring the interfacial region for photoelectron spectroscopy. Self-assembled monolayers (SAM) were utilized to induce dipoles of various magnitudes at the interface. Additionally, SAMs of molecules with varying dipolar characteristics were mixed into spatially organized structures to systematically vary the apparent work function. Polymer thin films were characterized by depositing films of varying thicknesses on numerous substrates with and without interfacial modifications. Hard X-ray photoelectron spectroscopy (HAXPES) was performed to evaluate a buried interface between indium tin oxide (ITO), treated under various conditions, and poly(3-hexylthiophene) (P3HT). Conducting polymer films were found to be sufficiently conducting such that no significant charge redistribution in the polymer films was observed. Consequently, a further departure from uniform substrates was taken whereby electrically disconnected regions of the substrate presented ideally insulating interfacial contacts. In order to accomplish this novel strategy, interdigitated electrodes were used as the substrate. Conducting fingers of one half of the electrodes were electrically grounded while the other set of electrodes were electronically floating. This allowed for the evaluation of substrate charging on photoelectron spectra (SCOPES) in the presence of overlying semiconducting thin films. Such an experiment has never before been reported. This concept was developed out of the previous experiments on interfacial modification and thin film depositions and presents new opportunities for understanding chemical and electronic changes in a multitude of materials and interfaces.

  19. Investigation of sulfur forms and transformation during the co-combustion of sewage sludge and coal using X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Li, Pei-Sheng; Hu, Yi; Yu, Wan; Yue, Ya-Nan; Xu, Qiao; Hu, Song; Hu, Nian-Su; Yang, Jun

    2009-08-15

    X-ray photoelectron spectroscopy was used to investigate the characteristics and evolution of sulfur (S) in mixtures of bituminous coal and sewage sludge (SS) and their chars during isothermal combustion. Five groups of mixtures with SS content of 0%, 10%, 20%, 30% and 100%, were examined at different burn-off ratios (beta) of 0, 30%, 50%, 70% and 100%. The S in the coal mainly exist as the forms of mercaptan (S1), sulfide (S2), thiophene (S3), sulfoxide (S4), sulfone (S5) and sulfate (S6). During the coal combustion process, the content of S1 and S2 decreased, while that of S3 and S5 increased in the early stage and decreased in the late stage. The S4 content increased throughout the entire process of combustion. Small amount of S6 was detected, showing a fluctuated pattern. The trend of S1, S2, S5 and S6 in SS was alike with that in coal, whereas S4 decreased at the end of combustion. The changing process of S3 in SS was opposite to that of coal, while the composition of S in the mixtures resulted from the mixing of coal and SS. The transformation of each functional group during co-combustion were correlated with their transformation characteristics during the mono-combustion of coal and SS, and no obvious interaction was observed, which demonstrated that the coal-origin and SS-origin sulfur in mixtures kept their own characteristics in the combustion. SS may accumulate on the solid surface as alpha increase, resulting its significant influence on the evolution of each form of S. When alpha was low, most of the S-contained functional groups presented the characteristics of coal. The percentage of coal-origin functional groups declined as alpha increased. The transforming trends of most functional groups were similar with that of SS when alpha reached 30%.

  20. Interaction of human plasma fibrinogen with commercially pure titanium as studied with atomic force microscopy and X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Keere, Isabel Van De; Willaert, Ronnie; Hubin, Annick; Vereecken, Jean

    2008-03-04

    The surface of a biomaterial interacts with the body fluid upon implantation in the human body. The biocompatibility of a material is strongly influenced by the adsorption of proteins onto the surface. Titanium is frequently used as a biomaterial for implants in orthopedics and cardiovascular devices. Understanding the biocompatibility is very important to improve implants. The surface chemistry of an implant material and its influence on the interaction with body fluid is crucial in that perspective. The main goal of this study was to investigate the conformation of human plasma fibrinogen (HPF) adsorbed on commercially pure titanium (CP Ti) on a molecular level by means of ex situ atomic force microscopy (AFM). With X-ray photoelectron spectroscopy combined with argon ion beam depth profiling, it was shown that the oxide layer present at the surface was mainly composed of TiO2, with a small percentage of Ti2O3. Ex situ AFM imaging showed the conformation of HPF on CP Ti. Single molecules and aggregates of fibrinogen were observed. The trinodular structure of single HPF molecules (two spherical D domains at the distal ends of the extended molecule and the central spherical E domain) adsorbed onto CP Ti was visualized. Aggregate formation through the connection of the D domains of the HPF molecules was observed on CP Ti. The alphaC domains of HPF were not visible on CP Ti. The ex situ AFM images indicated conformational changes of HPF upon adsorption onto CP Ti. The conformation of the adsorbed HPF molecules was different on mica and titanium. The difference in wettability between both substrates caused a larger spread of the protein on the CP Ti surface and thus resulted in a larger perturbation to the native structure of HPF as compared to mica.

  1. Advanced analysis tool for X-ray photoelectron spectroscopy profiling: Cleaning of perovskite SrTiO{sub 3} oxide surface using argon cluster ion source

    Energy Technology Data Exchange (ETDEWEB)

    Aureau, D., E-mail: damien.aureau@uvsq.fr [Institut Lavoisier de Versailles, (UMR 8180) Université de Versailles-Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Ridier, K. [Institut Lavoisier de Versailles, (UMR 8180) Université de Versailles-Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Groupe d' Étude de la Matière Condensée (UMR 8635) Université de Versailles Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Bérini, B.; Dumont, Y.; Keller, N. [Groupe d' Étude de la Matière Condensée (UMR 8635) Université de Versailles Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Vigneron, J.; Bouttemy, M.; Etcheberry, A. [Institut Lavoisier de Versailles, (UMR 8180) Université de Versailles-Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Fouchet, A. [Groupe d' Étude de la Matière Condensée (UMR 8635) Université de Versailles Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France)

    2016-02-29

    This article shows the comparison between three different ionic bombardments during X-ray photoelectron spectroscopy (XPS) studies of single crystalline SrTiO{sub 3} (STO) substrates. The abrasion using a “cluster argon ion source” is compared with the standard “monoatomic Ar”. The influence of the energy of the monoatomic ions used is clearly demonstrated. While the chemically adsorbed species on the STO surface are removed, such bombardment strongly modifies the surface. A reduction of part of the titanium atoms and the appearance of a different chemical environment for surface strontium atoms are observed. Implantation of argon ions is also detected. Cluster ion etching is used on oxide surface and, in this case only, due to a much lower kinetic energy per atom compared to monoatomic ions, the possibility to remove surface contaminants at the surface without modification of the XP spectra is clearly demonstrated, ensuring that the stoichiometry of the surface is preserved. Such result is crucial for everybody working with oxide surfaces to obtain a non-modified XPS analysis. The progressive effect of this powerful tool allows the monitoring of the removal of surface contamination in the first steps of the bombardment which was not achievable with usual guns. - Highlights: • The effects of three argon etchings are studied as a function of time on SrTiO3 oxide. • A method for obtaining non-modified chemical analysis of oxides is presented. • The soft removal of adsorbed species thanks to argon cluster is demonstrated. • The damages induced on SrTiO3 surface by ionic bombardment are shown. • The influence of the kinetic energy of incoming Ar atoms is examined.

  2. Negative Ion Photoelectron Spectroscopy Reveals Remarkable Noninnocence of Ligands in Nickel Bis(dithiolene) Complexes [Ni(dddt)2](-) and [Ni(edo)2](.).

    Science.gov (United States)

    Liu, Xing; Hou, Gao-Lei; Wang, Xuefeng; Wang, Xue-Bin

    2016-05-12

    [Ni(dddt)2](-) (dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate) and [Ni(edo)2](-) (edo = 5,6-dihydro-1,4-dioxine-2,3-dithiolate) are two donor-type nickel bis(dithiolene) complexes, with the tendency of donating low binding energy electrons. These two structurally similar complexes differ only with respect to the outer atoms in the ligand framework where the former has four S atoms while the latter has four O atoms. Herein, we report a negative ion photoelectron spectroscopy (NIPES) study on these two complexes to probe the electronic structures of the anions and their corresponding neutrals. The NIPE spectra exhibit the adiabatic electron detachment energy (ADE) or, equivalently, the electron affinity (EA) of the neutral [Ni(L)2](0) to be relatively low for this type of complexes, 2.780 and 2.375 eV for L = dddt and edo, respectively. The 0.4 eV difference in ADEs shows a significant substitution effect for sulfur in dddt by oxygen in edo, i.e., noninnocence of the ligands, which has decreased the electronic stability of [Ni(edo)2](-) by lowering its electron binding energy by ∼0.4 eV. The observed substitution effect on gas-phase EA values correlates well with the measured redox potentials for [Ni(dddt)2](-/0) and [Ni(edo)2](-/0) in solutions. The singlet-triplet splitting (ΔEST) of [Ni(dddt)2](0) and [Ni(edo)2](0) is also determined from the spectra to be 0.57 and 0.53 eV, respectively. Accompanying DFT calculations and molecular orbital (MO) composition analyses show significant ligand contributions to the redox MOs and allow the components of the orbitals involved in each electronic transition and spectral assignments to be identified.

  3. An X-ray photoelectron spectroscopy study of surface changes on brominated and sulfur-treated activated carbon sorbents during mercury capture: performance of pellet versus fiber sorbents.

    Science.gov (United States)

    Saha, Arindom; Abram, David N; Kuhl, Kendra P; Paradis, Jennifer; Crawford, Jenni L; Sasmaz, Erdem; Chang, Ramsay; Jaramillo, Thomas F; Wilcox, Jennifer

    2013-12-03

    This work explores surface changes and the Hg capture performance of brominated activated carbon (AC) pellets, sulfur-treated AC pellets, and sulfur-treated AC fibers upon exposure to simulated Powder River Basin-fired flue gas. Hg breakthrough curves yielded specific Hg capture amounts by means of the breakthrough shapes and times for the three samples. The brominated AC pellets showed a sharp breakthrough after 170-180 h and a capacity of 585 μg of Hg/g, the sulfur-treated AC pellets exhibited a gradual breakthrough after 80-90 h and a capacity of 661 μg of Hg/g, and the sulfur-treated AC fibers showed no breakthrough even after 1400 h, exhibiting a capacity of >9700 μg of Hg/g. X-ray photoelectron spectroscopy was used to analyze sorbent surfaces before and after testing to show important changes in quantification and oxidation states of surface Br, N, and S after exposure to the simulated flue gas. For the brominated and sulfur-treated AC pellet samples, the amount of surface-bound Br and reduced sulfur groups decreased upon Hg capture testing, while the level of weaker Hg-binding surface S(VI) and N species (perhaps as NH4(+)) increased significantly. A high initial concentration of strong Hg-binding reduced sulfur groups on the surface of the sulfur-treated AC fiber is likely responsible for this sorbent's minimal accumulation of S(VI) species during exposure to the simulated flue gas and is linked to its superior Hg capture performance compared to that of the brominated and sulfur-treated AC pellet samples.

  4. Structures and chemical bonding of B3O3 (-/0) and B3O3H(-/0): A combined photoelectron spectroscopy and first-principles theory study.

    Science.gov (United States)

    Zhao, Li-Juan; Tian, Wen-Juan; Ou, Ting; Xu, Hong-Guang; Feng, Gang; Xu, Xi-Ling; Zhai, Hua-Jin; Li, Si-Dian; Zheng, Wei-Jun

    2016-03-28

    We present a combined photoelectron spectroscopy and first-principles theory study on the structural and electronic properties and chemical bonding of B3O3 (-/0) and B3O3H(-/0) clusters. The concerted experimental and theoretical data show that the global-minimum structures of B3O3 and B3O3H neutrals are very different from those of their anionic counterparts. The B3O3 (-) anion is characterized to possess a V-shaped OB-B-BO chain with overall C2 v symmetry (1A), in which the central B atom interacts with two equivalent boronyl (B≡O) terminals via B-B single bonds as well as with one O atom via a B=O double bond. The B3O3H(-) anion has a Cs (2A) structure, containing an asymmetric OB-B-OBO zig-zag chain and a terminal H atom interacting with the central B atom. In contrast, the C2 v (1a) global minimum of B3O3 neutral contains a rhombic B2O2 ring with one B atom bonded to a BO terminal and that of neutral B3O3H (2a) is also of C2 v symmetry, which is readily constructed from C2 v (1a) by attaching a H atom to the opposite side of the BO group. The H atom in B3O3H(-/0) (2A and 2a) prefers to interact terminally with a B atom, rather than with O. Chemical bonding analyses reveal a three-center four-electron (3c-4e) π hyperbond in the B3O3H(-) (2A) cluster and a four-center four-electron (4c-4e) π bond (that is, the so-called o-bond) in B3O3 (1a) and B3O3H (2a) neutral clusters.

  5. Effect of iron oxide reductive dissolution on the transformation and immobilization of arsenic in soils: New insights from X-ray photoelectron and X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Jian-Xin [Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China); School of River and Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074 (China); Wang, Yu-Jun, E-mail: yjwang@issas.ac.cn [Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China); Liu, Cun [Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China); Wang, Li-Hua; Yang, Ke [Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of sciences, Shanghai 201204 (China); Zhou, Dong-Mei, E-mail: dmzhou@issas.ac.cn [Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China); Li, Wei; Sparks, Donald L. [Environmental Soil Chemistry Group, Delaware Environmental Institute and Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19717-1303 United States (United States)

    2014-08-30

    Graphical abstract: - Highlights: • Immobility and transformation of As on different Eh soils were investigated. • μ-XRF, XANES, and XPS were used to gain As distribution and speciation in soil. • Sorption capacity of As on anaerobic soil was much higher than that on oxic soil. • Fe oxides reductive dissolution is a key factor for As sorption and transformation. - Abstract: The geochemical behavior and speciation of arsenic (As) in paddy soils is strongly controlled by soil redox conditions and the sequestration by soil iron oxyhydroxides. Hence, the effects of iron oxide reductive dissolution on the adsorption, transformation and precipitation of As(III) and As(V) in soils were investigated using batch experiments and synchrotron based techniques to gain a deeper understanding at both macroscopic and microscopic scales. The results of batch sorption experiments revealed that the sorption capacity of As(V) on anoxic soil was much higher than that on control soil. Synchrotron based X-ray fluorescence (μ-XRF) mapping studies indicated that As was heterogeneously distributed and was mainly associated with iron in the soil. X-ray absorption near edge structure (XANES), micro-X-ray absorption near edge structure (μ-XANES) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the primary speciation of As in the soil is As(V). These results further suggested that, when As(V) was introduced into the anoxic soil, the rapid coprecipitation of As(V) with ferric/ferrous ion prevented its reduction to As(III), and was the main mechanism controlling the immobilization of As. This research could improve the current understanding of soil As chemistry in paddy and wetland soils.

  6. High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Strocov, V. N., E-mail: vladimir.strocov@psi.ch; Schmitt, T.; Flechsig, U.; Schmidt, T.; Imhof, A.; Chen, Q.; Raabe, J. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland); Betemps, R.; Zimoch, D.; Krempasky, J. [Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland); Wang, X. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland); Institut de Physique de la Matiére Condensé, Ecole Polytechnique Fédéderale de Lausanne (Switzerland); Grioni, M. [Institut de Physique de la Matiére Condensé, Ecole Polytechnique Fédéderale de Lausanne (Switzerland); Piazzalunga, A. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland); Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Patthey, L. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland)

    2010-09-01

    Concepts and technical realization of the high-resolution soft X-ray beamline ADRESS at the Swiss Light Source are described. Optimization of the optical scheme for high resolution and photon flux as well as diagnostics tools and alignment strategies are discussed. The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for resonant inelastic X-ray scattering (RIXS) and angle-resolved photoelectron spectroscopy (ARPES) are described. The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0–180° rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well established scheme of plane-grating monochromator operating in collimated light. The ultimate resolving power E/ΔE is above 33000 at 1 keV photon energy. The choice of blazed versus lamellar gratings and optimization of their profile parameters is described. Owing to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, the beamline is capable of delivering high photon flux up to 1 × 10{sup 13} photons s{sup −1} (0.01% BW){sup −1} at 1 keV. Ellipsoidal refocusing optics used for the RIXS endstation demagnifies the vertical spot size down to 4 µm, which allows slitless operation and thus maximal transmission of the high-resolution RIXS spectrometer delivering E/ΔE > 11000 at 1 keV photon energy. Apart from the beamline optics, an overview of the control system is given, the diagnostics and software tools are described, and strategies used for the optical alignment are discussed. An introduction to the concepts and instrumental realisation of the ARPES and RIXS endstations is given.

  7. Competition between organics and bromide at the aqueous solution-air interface as seen from ozone uptake kinetics and X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Lee, Ming-Tao; Brown, Matthew A; Kato, Shunsuke; Kleibert, Armin; Türler, Andreas; Ammann, Markus

    2015-05-14

    A more detailed understanding of the heterogeneous chemistry of halogenated species in the marine boundary layer is required. Here, we studied the reaction of ozone (O3) with NaBr solutions in the presence and absence of citric acid (C6H8O7) under ambient conditions. Citric acid is used as a proxy for oxidized organic material present at the ocean surface or in sea spray aerosol. On neat NaBr solutions, the observed kinetics is consistent with bulk reaction-limited uptake, and a second-order rate constant for the reaction of O3 + Br(-) is 57 ± 10 M(-1) s(-1). On mixed NaBr-citric acid aqueous solutions, the uptake kinetics was faster than that predicted by bulk reaction-limited uptake and also faster than expected based on an acid-catalyzed mechanism. X-ray photoelectron spectroscopy (XPS) on a liquid microjet of the same solutions at 1.0 × 10(-3)-1.0 × 10(-4) mbar was used to obtain quantitative insight into the interfacial composition relative to that of the bulk solutions. It revealed that the bromide anion becomes depleted by 30 ± 10% while the sodium cation gets enhanced by 40 ± 20% at the aqueous solution-air interface of a 0.12 M NaBr solution mixed with 2.5 M citric acid in the bulk, attributed to the role of citric acid as a weak surfactant. Therefore, the enhanced reactivity of bromide solutions observed in the presence of citric acid is not necessarily attributable to a surface reaction but could also result from an increased solubility of ozone at higher citric acid concentrations. Whether the acid-catalyzed chemistry may have a larger effect on the surface than in the bulk to offset the effect of bromide depletion also remains open.

  8. Electronic structure of the (Nd1−xDyx2Fe14B (0 ≤ x ≤ 1 system studied by X-ray photoelectron spectroscopy

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2015-09-01

    Full Text Available Systematic characterization of electronic structures in the (Nd1−xDyx2Fe14B system, especially the 4f behavior, provides an insight to the physical nature of the evolution of magnetic properties. A series of X-ray photoelectron spectroscopy (XPS core-level and valence-band spectra were used to study the electronic structures. It was found that substitution of Dy for Nd in Nd2Fe14B results in a nonlinear variation in the evolution of electronic structures. Only the finite coupling between the Nd 4f states and the Fe 3d states is found at both the Nd-rich regime and the Dy-rich regime. When the Dy concentration and the Nd concentration approach to be equal, a strong coupling between the Nd 4f states and the Fe 3d states is found, which results in a bonding state between them. Additionally, the 4f components in the (Nd1−xDyx2Fe14B system are ascribed to three parts: 1 the individual contribution of the Dy 4f states, which emerges just after the Dy-substitution; 2 the contribution of the coupling between the Nd 4f states and the Dy 4f states, which arises only when 0.4 ≤ x ≤ 0.6; 3 the associated contributions of the Nd 4f states and the Dy 4f states, where the contribution of the Nd 4f states and that of the Dy 4f states are prominent in the Nd-rich regime and Dy-rich regime, respectively.

  9. X-ray photoelectron spectroscopy study of fluorine-treated YBa sub 2 Cu sub 3 O sub 7 minus. delta. crystals

    Energy Technology Data Exchange (ETDEWEB)

    Tressaud, A.; Amine, K.; Chaminade, J.P.; Etourneau, J. (Laboratoire de Chimie du Solide du CNRS, Universite de Bordeaux I, 33405 Talence Cedex, (France)); Duc, T.M. (Institut de Physique Nucleaire, IN2P3-CNRS, Universite Claude Bernard, 69622 Villeurbanne Cedex, (France)); Sartre, A. (Science et Surface S.A., 69260 Charbonnieres, (France))

    1990-07-01

    An x-ray photoelectron-spectroscopy study of flux-grown YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} crystals left in moist atmospheric conditions has shown some aspects of the degradation process. Besides peaks which correspond to YO and BaO bonding in the superconducting phase, higher binding-energy components can be attributed to BaCO{sub 3}, YOH, and/or YCO{sub 3} bonding. An x-ray photoreduction of the copper species is observed in the ultrahigh vacuum. Fluorine-gas treatments carried out at low temperature drastically modify the surface properties of the crystals. The peaks attributed to MO bonding (M=Y, Ba, or Cu) disappear and are substituted by MF bonding with a subsequent increase in {ital E}{sub {ital b}}. In the F 1{ital s} region, the peak corresponding to those bondings is observed around {ital E}{sub {ital b}} {congruent}684.5 eV, a value which is in agreement with those claimed for the corresponding inorganic fluorides. The signature of those surface fluorides remains, even when the samples are left for long periods in moist air. Within the F 1{ital s} envelope, chemisorbed fluoro species with {ital E}{sub {ital b}} {congruent}686.5 eV are observed, especially when the fluorination process is performed at room temperature. These species are eliminated by vacuum annealing at 350 {degree}C. In specific conditions, a high-binding-energy contribution arises ({ital E}{sub {ital b}} {congruent}689 eV) which can be ascribed to the formation of surface carbon fluoride.''

  10. Laser photoelectron spectroscopy of ions

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, G.B. [Univ. of Colorado, Boulder (United States)

    1993-12-01

    During the last year the author has (a) completed a review article that critically contrasts three methods to measure R-H bond energies, (b) finished a spectroscopic study of the phenylnitrene anion, and (c) successfully completed an overhaul of the light source of the photodetachment spectrometer. The new light source is based on an Ar III laser that provides approximately 100 W of 3.531 eV photons.

  11. Surface and sub-surface oxidation of {alpha}-Cu-(17 at.%)Al(1 0 0) studied by X-ray photo-electron spectroscopy and low energy He{sup +} scattering spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kravchuk, T. [Department of Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Akhvlediani, R. [Department of Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Hoffman, A. [Department of Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel)]. E-mail: choffman@tx.technion.ac.il

    2005-04-01

    In this study the initial stages of oxidation of the {alpha}-Cu-(17 at.%)Al(1 0 0) single crystal oriented alloy surface was investigated by X-ray photo-electron spectroscopy and low energy He{sup +} scattering spectroscopy. It was found that oxygen adsorption can be divided in two sequential stages: (i) a fast process, up to 15-20 L exposure, in which oxygen adsorbs on the alloy's surface resulting mostly in the formation of Al-O chemisorbed bonds; and (ii) a slower process during which oxygen adsorbs forming Cu-O and Al-O chemisorbed bonds concurrent with diffusion of O to the sub-surface and Al segregation to the surface region. The surface oxidation rate is much higher than the sub-surface one. The rate of Al segregation increases with oxygen exposure and involves both surface and sub-surface regions. Annealing of the oxidized alloy surface results in a pronounced segregation of Al and formation of an aluminum oxide layer.

  12. Simulation of attosecond-resolved imaging of the plasmon electric field in metallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Prell, James S.; Borja, Lauren J. [Department of Chemistry, University of California, Berkeley, CA, 94720-1460 (United States); Neumark, Daniel M. [Department of Chemistry, University of California, Berkeley, CA, 94720-1460 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720 (United States); Leone, Stephen R. [Department of Chemistry, University of California, Berkeley, CA, 94720-1460 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720 (United States); Department of Physics, University of California, Berkeley, CA, 94720-1460 (United States)

    2013-02-15

    Sub-cycle photoelectron streaking from silver plasmonic nanospheres is simulated using few-cycle laser pulses tuned both on and off the plasmon resonance (376 nm vs 800 nm, respectively) to initiate the plasmon. Phase-locked, isolated attosecond XUV pulses induce photoemission from the nanospheres, and two different types of streaking of the photoelectrons occur simultaneously due to the laser and plasmon electric fields. Streaking is simulated over a wide range of excitation pulse intensities, and final velocity distributions for the photoelectrons emitted at different times are calculated. The resulting velocity distributions exhibit several characteristics attributable to the plasmon electric field. The dipole moment amplitude can be reconstructed using velocity map imaging or time-of-flight photoelectron velocity measurements without separate measurement of the laser electric field or deconvolution using an assumed streaking trace shape. These results indicate that photoelectron experiments in table-top set-ups can provide unprecedented spatio-temporal information about sub-cycle plasmon dynamics in metallic nanostructures. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Circularly Polarized Attosecond Pulses and Molecular Atto-Magnetism

    CERN Document Server

    Bandrauk, Andre D

    2014-01-01

    Various schemes are presented for the generation of circularly polarized molecular high-order harmonic generation (MHOHG) from molecules. In particular it is shown that combinations of counter-rotating circularly polarized pulses produce the lowest frequency Coriolis forces with the highest frequency recollisions, thus generating new harmonics which are the source of circular polarized attosecond pulses (CPAPs). These can be used to generate circularly polarized electronic currents in molecular media on attosecond time scale. Molecular attosecond currents allow then for the generation of ultrashort magnetic field pulses on the attosecond time scale, new tools for molecular atto-magnetism (MOLAM).

  14. An Experimentally Based Description of the Ground-state Wavefunction for Two Weakly Coupled Electrons by Photoelectron Spectroscopy and Magnetic Susceptibility Measurements

    OpenAIRE

    Rankin, Richard; Seddon, Elaine A.; Teuben, Jan H.; Jonkman-Beuker, Anneke H.; Boer, Dirk K.G. de

    1981-01-01

    It is possible to extract values for the transfer energy, t, and the Coulomb interaction, U, in hydrogen-like systems from a combination of photoelectron and magnetic data, as both the form of the photoelectron spectrum and the exchange splitting are determined by these quantities. This procedure is used to evaluate the ground-state wavefunction for the two weakly coupled Ti 3d electrons in (C10H8)(C5H5)2Ti2Cl2.

  15. Soft X-Ray and Vacuum Ultraviolet Based Spectroscopy of the Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J G

    2011-03-17

    The subjects of discussion included: VUV photoelectron spectroscopy, X-ray photoelectron spectroscopy, Synchrotron-radiation-based photoelectron spectroscopy, Soft x-ray absorption spectroscopy, Soft x-ray emission spectroscopy, Inverse photoelectron spectroscopy, Bremstrahlung Isochromat Spectroscopy, Low energy IPES, Resonant inverse photoelectron spectroscopy.

  16. Attosecond pulse shaping around a Cooper minimum

    CERN Document Server

    Schoun, S B; Wheeler, J; Roedig, C; Agostini, P; DiMauro, L F; Schafer, K J; Gaarde, M B

    2013-01-01

    High harmonic generation (HHG) is used to measure the spectral phase of the recombination dipole matrix element (RDM) in argon over a broad frequency range that includes the 3p Cooper minimum (CM). The measured RDM phase agrees well with predictions based on the scattering phases and amplitudes of the interfering s- and d-channel contributions to the complementary photoionization process. The reconstructed attosecond bursts that underlie the HHG process show that the derivative of the RDM spectral phase, the group delay, does not have a straight-forward interpretation as an emission time, in contrast to the usual attochirp group delay. Instead, the rapid RDM phase variation caused by the CM reshapes the attosecond bursts.

  17. Attosecond physics at a nanoscale metal tip

    Directory of Open Access Journals (Sweden)

    Lemell Christoph

    2013-03-01

    Full Text Available With few-cycle laser oscillator pulses at 800 nm we observe strong-field and attosecond physics phenomena in electron spectra recorded at a nanoscale tungsten tip. We observe the rescattering plateau as well as a strong carrier-envelope phase dependence of the spectra. We model the results with the semiclassical three-step model as well as with time-dependent density functional theory.

  18. Photoelectron spectroscopy at a free-electron laser. Investigation of space-charge effects in angle-resolved and core-level spectroscopy and realizaton of a time-resolved core-level photoemission experiment

    Energy Technology Data Exchange (ETDEWEB)

    Marczynski-Buehlow, Martin

    2012-01-30

    The free-electron laser (FEL) in Hamburg (FLASH) is a very interesting light source with which to perform photoelectron spectroscopy (PES) experiments. Its special characteristics include highly intense photon pulses (up to 100 J/pulse), a photon energy range of 30 eV to 1500 eV, transverse coherence as well as pulse durations of some ten femtoseconds. Especially in terms of time-resolved PES (TRPES), the deeper lying core levels can be reached with photon energies up to 1500 eV with acceptable intensity now and, therefore, element-specific, time-resolved core-level PES (XPS) is feasible at FLASH. During the work of this thesis various experimental setups were constructed in order to realize angle-resolved (ARPES), core-level (XPS) as well as time-resolved PES experiments at the plane grating monochromator beamline PG2 at FLASH. Existing as well as newly developed systems for online monitoring of FEL pulse intensities and generating spatial and temporal overlap of FEL and optical laser pulses for time-resolved experiments are successfully integrated into the experimental setup for PES. In order to understand space-charge effects (SCEs) in PES and, therefore, being able to handle those effects in future experiments using highly intense and pulsed photon sources, the origin of energetic broadenings and shifts in photoelectron spectra are studied by means of a molecular dynamic N-body simulation using a modified Treecode Algorithm for sufficiently fast and accurate calculations. It turned out that the most influencing parameter is the ''linear electron density'' - the ratio of the number of photoelectrons to the diameter of the illuminated spot on the sample. Furthermore, the simulations could reproduce the observations described in the literature fairly well. Some rules of thumb for XPS and ARPES measurements could be deduced from the simulations. Experimentally, SCEs are investigated by means of ARPES as well as XPS measurements as a function of

  19. X-ray photoelectron spectroscopy of oxygen-containing layers formed by a linear potential scan on stepped gold (111) films in aqueous 1 M sulphuric acid

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Nieto, Felipe J. [Instituto de Investigaciones Fisicoquimica Teoricas y Aplicadas INIFTA, Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Cientificas y Tecnicas Sucursal 4, Casilla de Correo 16, (1900) La Plata (Argentina); Member of Comision de Investigaciones Cientificas de la Provincia de Buenos Aires (Argentina)], E-mail: rodrini@inifta.unlp.edu.ar; Fachini, Esteban; Cabrera, Carlos R. [Department of Chemistry, University of Puerto Rico, Rio Piedras Campus, P.O. Box 23346, San Juan, 00931-3346 (Puerto Rico); Arvia, Alejandro J. [Instituto de Investigaciones Fisicoquimica Teoricas y Aplicadas INIFTA, Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Cientificas y Tecnicas Sucursal 4, Casilla de Correo 16, (1900) La Plata (Argentina)

    2009-01-01

    X-ray photoelectron spectroscopy (XPS) data of oxygen-containing layers (O-layers) made on stepped gold (111) film electrodes from aqueous 1 M sulphuric acid by single linear potential scans at 0.10 V s{sup -1} and 298 K are reported. The potential scan covered from the open circuit potential to anodic switching potential E{sub as} = 2.50 V versus normal hydrogen electrode (NHE) and holding times at E{sub as} in the range 30-300 s. The anodic charge density q{sub a} determined from the oxidation and reduction voltammetric scan is in the range 0.20 {<=} q{sub a} {<=} 2.5 mC cm{sup -2}. For the potential E = 0.5 V, in the absence of O-layers, the S 2p core level spectrum indicates the presence of sulphate/bisulphate adsorbates. For E{sub as} > 1.3 V, the O 1s core level spectrum involves the contribution from water, OH- and O-species. These spectra are deconvoluted utilising either three or four Gaussian contributions with values of peaked binding energy and full width at half-maximum height (FWMH) in good agreement with expectations. The envelope of these XPS O 1s signals after correction for the contribution of sulphate/bisulphate adsorbates and adventitious carbon approaches the XPS signal that has been reported for the core level spectrum in the O 1s region of oxidised gold surfaces produced by laser pulses at different molecular oxygen pressures. The O/OH concentration ratio in the O-layer increases with E{sub as} ageing time t{sub ag} and cathodic charge density q{sub c}. The hydrous nature of the O-layer, evaluated through the analysis of the core level spectra in the O 1s region, decreases as E{sub as} and t{sub ag} are increased. Results are interesting to unravel the composition and structure of electrochemically grown O-layers at the surface of the gold substrate, and the influence of the history of these O-layers on the respective XPS features.

  20. X-ray photoelectron spectroscopy studies of the electronic structure of superconducting Nb{sub 2}SnC and Nb{sub 2}SC

    Energy Technology Data Exchange (ETDEWEB)

    Romero, M.; Huerta, L.; Akachi, T. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México D.F. 04510 (Mexico); Llamazares, J.L. Sánchez [Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, Col. Lomas 4a, San Luis Potosí, S.L.P. 78216 (Mexico); Escamilla, R., E-mail: rauleg@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México D.F. 04510 (Mexico)

    2013-12-05

    Highlights: •XPS was used to investigate chemical shift in the Nb{sub 2}SnC and Nb{sub 2}SC compounds. •Valence band of the Nb{sub 2}SnC and Nb{sub 2}SC compounds was studied by XPS. •Positive and negative chemical shift are observed in the Nb{sub 2}SnC and Nb{sub 2}SC. •The charge transfer model can be applicable to the Nb{sub 2}SnC and Nb{sub 2}SC compounds. •The decrease of the N(E{sub F}) of Nb{sub 2}SC respect to Nb{sub 2}SnC explain the decrease of T{sub c}. -- Abstract: X-ray photoelectron spectroscopy (XPS) was used to investigate the binding energies and valence band of the Nb{sub 2}SnC and Nb{sub 2}SC compounds. The Nb 3d{sub 5/2}, Sn 3d{sub 5/2}, S 2p{sub 3/2} and C 1s core levels associated with the chemical states of Nb{sub 2}SnC and Nb{sub 2}SC were identified. The spectra for Nb{sub 2}SnC revealed Nb and Sn oxides on the surface of the sample, mainly Nb{sub 2}O{sub 5} and SnO{sub 2}, while the Nb{sub 2}SC only Nb{sub 2}O{sub 5} oxide. After Ar{sup +} ion etching the intensity of the oxides decreased in both samples. Comparing the Nb 3d, Sn 3d, S 2p and C 1s core levels with metallic Nb, Sn, S and C reference materials, we observed a positive chemical shift for Nb 3d{sub 5/2} and a negative chemical shift for C 1s in both samples. These results suggest that the charge transfer model can be applicable to the Nb{sub 2}SnC and Nb{sub 2}SC compounds. Finally, the decrease in the T{sub c} in the Nb{sub 2}SC compound respect to Nb{sub 2}SnC might be associated to decrease in the density of states N(E{sub F})

  1. Evaluation of the band alignment and valence plasmonic features of a DIBS grown Ga-doped Mg0.05Zn0.95O/CIGSe heterojunction by photoelectron spectroscopy

    Science.gov (United States)

    Awasthi, Vishnu; Pandey, Sushil Kumar; Kumar, Shailendra; Mukherjee, C.; Gupta, Mukul; Mukherjee, Shaibal

    2015-12-01

    The bandgap alignment of a Ga-doped MgZnO (GMZO)/CIGSe heterojunction exposed to short duration Ar+  ion beam sputtering has been investigated by ultraviolet photoelectron spectroscopy measurement. The offset values at the valence and conduction band of the GMZO/CIGSe hetrojunction are calculated to be 2.69 and  -0.63 eV, respectively. Moreover, the valence band onsets of GMZO and CIGSe thin films before and after few minutes Ar+ ion sputtering have been investigated. The presented study demonstrates the photoelectron-induced generation of resonant valence bulk and surface plasmonic features of various metal and metal oxide nanoclusters embedded within a GMZO matrix. The presence of such nanoclusters is proven to be beneficial in realizing cost-effective, ultra-thin, and high-performance photovoltaics based on the heterojunction.

  2. Espectroscopia de fotoelétrons de limiares de átomos e moléculas Atomic and molecular threshold photoelectron spectroscopy

    Directory of Open Access Journals (Sweden)

    Maria Cristina Andreolli Lopes

    2006-02-01

    Full Text Available A threshold photoelectron spectrometer applied to the study of atomic and molecular threshold photoionization processes is described. The spectrometer has been used in conjunction with a toroidal grating monochromator at the National Synchrotron Radiation Laboratory (LNLS, Brazil. It can be tuned to accept threshold electrons (< 20 meV and work with a power resolution of 716 (~18 meV at 12 eV with a high signal/noise ratio. The performance of this apparatus and some characteristics of the TGM (Toroidal Grating Monochromator beam line of LNLS are described and discussed by means of argon, O2 and N2 threshold photoelectron spectra.

  3. Structure of reactively sputter deposited tin-nitride thin films: A combined X-ray photoelectron spectroscopy, in situ X-ray reflectivity and X-ray absorption spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Luetzenkirchen-Hecht, Dirk [Fachbereich C-Physik, Bergische Universitaet Wuppertal, Gaussstr. 20, D-42097 Wuppertal (Germany)]. E-mail: dirklh@uni-wuppertal.de; Frahm, Ronald [Fachbereich C-Physik, Bergische Universitaet Wuppertal, Gaussstr. 20, D-42097 Wuppertal (Germany)

    2005-12-22

    Amorphous tin-nitride thin films were prepared by reactive sputter deposition on smooth float glass substrates in a vacuum chamber with an integrated small magnetron source. The films were investigated using in situ reflection mode X-ray absorption spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS). Both the X-ray absorption near edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS) were analysed, yielding bond distances, coordination numbers and Debye-Waller factors. XPS yields the chemical composition and the binding state of the constituents of the films, specular X-ray reflectivity allows the determination of the sample density and of the roughness and its changes with film thickness. The results were compared to those of crystalline Sn{sub 3}N{sub 4}, indicating that the electronic and atomic structure of the amorphous films determined by EXAFS data analysis are very similar to the stoichiometric reference compound. Two different Sn-N interactions with about 2.09 and 2.19 A bond distance and 4 and 6 nearest neighbours, respectively, are present. These bond distances are slightly relaxed compared to the crystalline reference material, which is consistent with the sample density, which is reduced by about 8% in comparison to Sn{sub 3}N{sub 4}. XPS as well as XANES revealed a Sn valence of about 4+ and the presence of nitric bonds, while XPS also suggests that the nitride is slightly decomposed under X-ray irradiation in ultra-high vacuum.

  4. Attosecond nonlinear polarization and light-matter energy transfer in solids

    Science.gov (United States)

    Sommer, A.; Bothschafter, E. M.; Sato, S. A.; Jakubeit, C.; Latka, T.; Razskazovskaya, O.; Fattahi, H.; Jobst, M.; Schweinberger, W.; Shirvanyan, V.; Yakovlev, V. S.; Kienberger, R.; Yabana, K.; Karpowicz, N.; Schultze, M.; Krausz, F.

    2016-06-01

    Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.

  5. Attosecond nonlinear polarization and light-matter energy transfer in solids.

    Science.gov (United States)

    Sommer, A; Bothschafter, E M; Sato, S A; Jakubeit, C; Latka, T; Razskazovskaya, O; Fattahi, H; Jobst, M; Schweinberger, W; Shirvanyan, V; Yakovlev, V S; Kienberger, R; Yabana, K; Karpowicz, N; Schultze, M; Krausz, F

    2016-05-23

    Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.

  6. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry characterization of aging effects on the mineral fibers treated with aminopropylsilane and quaternary ammonium compounds

    DEFF Research Database (Denmark)

    Zafar, Ashar; Schjødt-Thomsen, Jan; Sodhi, R.

    2012-01-01

    X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry were used to investigate the aging effects on the aminopropylsilane (APS) and quaternary ammonium surfactant-treated mineral fibers. APS-coated mineral fiber samples were treated with cationic surfactant...... (PCA) was applied to the time-of-flight secondary ion mass spectrometry spectra, and an increase in the intensities of APS characteristic peaks were observed after aging. The observed increase in the signals of APS originates from underlying silanized fibers after the removal of the surfactant...

  7. Regioisomer-specific electron affinities and electronic structures of C70 para-Adducts at polar and equatorial positions with (bromo)benzyl radicals: photoelectron spectroscopy and theoretical Study

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Gao-Lei; Li, Lei-Jiao; Li, Shu-Hui; Sun, Zhong-Ming; Gao, Xiang; Wang, Xue-Bin

    2016-07-28

    Negative ion photoelectron spectroscopy shows interesting regioisomer-specific electron affinities (EAs) of 2,5– and 7,23– para-adducts of C70 [(ArCH2)2C70] (Ar = Ph, o-, m-, and p-BrC6H4). Their EA values are larger than that of C70 by 5-150 meV with the 2,5– polar adducts’ EAs being higher than their corresponding 7,23– equatorial counterparts, exhibiting appreciable EA tunable ranges and regioisomer specificity. Density functional theory (DFT) calculations reproduce both the experimental EA values and EA trends very well.

  8. Correlation between Charge State of Insulating NaCl Surfaces and Ionic Mobility Induced by Water Adsorption: A Combined Ambient Pressure X-ray Photoelectron Spectroscopy and Scanning Force Microscopy Study

    Energy Technology Data Exchange (ETDEWEB)

    Verdaguer, Albert; Jose Segura, Juan; Fraxedas, Jordi; Bluhm, Hendrik; Salmeron, Miquel

    2008-09-03

    In situ ambient pressure X-ray photoelectron spectroscopy (APPES) and scanning force microscopy were used to characterize the surface discharge induced by water layers grown on (001) surfaces of sodium chloride single crystals. The APPES studies show that both kinetic energy (KE) and full width at half-maximum (FWHM) of the Na 2s and Cl 2p core level peaks, monitored as a function of relative humidity (RH), mimic surface conductivity curves measured using scanning force microscopy. The KE position and FWHM of the core level peaks therefore are directly related to the solvation and diffusion of ions at the NaCl(100) surface upon adsorption of water.

  9. Core-level spectra and binding energies of transition metal nitrides by non-destructive x-ray photoelectron spectroscopy through capping layers

    Science.gov (United States)

    Greczynski, G.; Primetzhofer, D.; Lu, J.; Hultman, L.

    2017-02-01

    We present the first measurements of x-ray photoelectron spectroscopy (XPS) core level binding energies (BE:s) for the widely-applicable group IVb-VIb polycrystalline transition metal nitrides (TMN's) TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN, and WN as well as AlN and SiN, which are common components in the TMN-based alloy systems. Nitride thin film samples were grown at 400 °C by reactive dc magnetron sputtering from elemental targets in Ar/N2 atmosphere. For XPS measurements, layers are either (i) Ar+ ion-etched to remove surface oxides resulting from the air exposure during sample transfer from the growth chamber into the XPS system, or (ii) in situ capped with a few nm thick Cr or W overlayers in the deposition system prior to air-exposure and loading into the XPS instrument. Film elemental composition and phase content is thoroughly characterized with time-of-flight elastic recoil detection analysis (ToF-E ERDA), Rutherford backscattering spectrometry (RBS), and x-ray diffraction. High energy resolution core level XPS spectra acquired with monochromatic Al Kα radiation on the ISO-calibrated instrument reveal that even mild etching conditions result in the formation of a nitrogen-deficient surface layer that substantially affects the extracted binding energy values. These spectra-modifying effects of Ar+ ion bombardment increase with increasing the metal atom mass due to an increasing nitrogen-to-metal sputter yield ratio. The superior quality of the XPS spectra obtained in a non-destructive way from capped TMN films is evident from that numerous metal peaks, including Ti 2p, V 2p, Zr 3d, and Hf 4f, exhibit pronounced satellite features, in agreement with previously published spectra from layers grown and analyzed in situ. In addition, the N/metal concentration ratios are found to be 25-90% higher than those obtained from the corresponding ion-etched surfaces, and in most cases agree very well with the RBS and ToF-E ERDA values. The N 1 s BE:s extracted from

  10. Atomic layer deposition of ultrathin Cu{sub 2}O and subsequent reduction to Cu studied by in situ x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dhakal, Dileep [Center for Microtechnologies—ZfM, Technische Universität Chemnitz, D-09107 Chemnitz (Germany); Assim, Khaybar; Lang, Heinrich [Institute of Chemistry, Inorganic Chemistry, Technische Universität Chemnitz, D-09107 Chemnitz (Germany); Bruener, Philipp; Grehl, Thomas [ION-TOF GmbH, Heisenbergstr. 15, D-48149 Münster (Germany); Georgi, Colin; Waechtler, Thomas; Ecke, Ramona; Schulz, Stefan E., E-mail: stefan.schulz@zfm.tu-chemnitz.de; Gessner, Thomas [Center for Microtechnologies—ZfM, Technische Universität Chemnitz, D-09107 Chemnitz, Germany and Fraunhofer Institute for Electronic Nano Systems—ENAS, Technologie-Campus 3, D-09126 Chemnitz (Germany)

    2016-01-15

    The growth of ultrathin (<5 nm) Ru-doped Cu{sub 2}O films deposited on SiO{sub 2} by atomic layer deposition (ALD) and Cu films by subsequent reduction of the Cu{sub 2}O using HCO{sub 2}H or CO is reported. Ru-doped Cu{sub 2}O has been deposited by a mixture of 16: 99 mol. % of [({sup n}Bu{sub 3}P){sub 2}Cu(acac)] as Cu precursor and 17: 1 mol. % of [Ru(η{sup 5}-C{sub 7}H{sub 11})(η{sup 5}-C{sub 5}H{sub 4}SiMe{sub 3})] as Ru precursor. The catalytic amount of Ru precursor was to support low temperature reduction of Cu{sub 2}O to metallic Cu by formic acid (HCO{sub 2}H) on arbitrary substrate. In situ x-ray photoelectron spectroscopy investigations of the Cu{sub 2}O ALD film indicated nearly 1 at. % of carbon contamination and a phosphorous contamination below the detection limit after sputter cleaning. Systematic investigations of the reduction of Ru-doped Cu{sub 2}O to metallic Cu by HCO{sub 2}H or CO as reducing agents are described. Following the ALD of 3.0 nm Cu{sub 2}O, the ultrathin films are reduced between 100 and 160 °C. The use of HCO{sub 2}H at 110 °C enabled the reduction of around 90% Cu{sub 2}O. HCO{sub 2}H is found to be very effective in the removal of oxygen from Ru-doped Cu{sub 2}O films with 2.5–4.7 nm thickness. In contrast, CO was effective for the removal of oxygen from the Cu{sub 2}O films only below 3.0 nm at 145 °C. Root mean square surface roughness of 0.4 ± 0.1 nm was observed from atomic force microscopy (AFM) investigations after the ALD of Cu{sub 2}O, followed by the subsequent reduction of 3.0 nm Cu{sub 2}O using either HCO{sub 2}H at 110 °C or CO at 145 °C on SiO{sub 2}. Furthermore, ex situ low energy ion scattering and AFM investigations confirmed that the Cu{sub 2}O film after ALD and Cu films after subsequent reduction was continuous on the SiO{sub 2} substrate.

  11. Molecular-orbital decomposition of the ionization continuum for a diatomic molecule by angle- and energy-resolved photoelectron spectroscopy. I. Formalism

    Science.gov (United States)

    Park, Hongkun; Zare, Richard N.

    1996-03-01

    A theoretical formalism is developed for the quantum-state-specific photoelectron angular distributions (PADs) from the direct photoionization of a diatomic molecule in which both the ionizing state and the state of the ion follow Hund's case (b) coupling. The formalism is based on the molecular-orbital decomposition of the ionization continuum and therefore fully incorporates the molecular nature of the photoelectron-ion scattering within the independent electron approximation. The resulting expression for the quantum-state-specific PADs is dependent on two distinct types of dynamical quantities, one that pertains only to the ionization continuum and the other that depends both on the ionizing state and the ionization continuum. Specifically, the electronic dipole-moment matrix element rlλ exp(iηlλ) for the ejection of a photoelectron with orbital angular momentum quantum number l making a projection λ on the internuclear axis is expressed as ΣαλŪlαλλ exp (iπτ¯αλλ) Mαλλ, where Ūλ is the electronic transformation matrix, τ¯αλλ is the scattering phase shift associated with the αλth continuum molecular orbital, and Mαλλ is the real electronic dipole-moment matrix element that connects the ionizing orbital to the αλth continuum molecular orbital. Because Ūλ and τ¯αλλ depend only on the dynamics in the ionization continuum, this formalism allows maximal exploitation of the commonality between photoionization processes from different ionizing states. It also makes possible the direct experimental investigation of scattering matrices for the photoelectron-ion scattering and thus the dynamics in the ionization continuum by studying the quantum-state-specific PADs, as illustrated in the companion article on the photoionization of NO.

  12. Near threshold studies of photoelectron satellites

    Energy Technology Data Exchange (ETDEWEB)

    Heimann, P.A.

    1986-11-01

    Photoelectron spectroscopy and synchrotron radiation have been used to study correlation effects in the rare gases: He, Ne, Ar, Kr, and Xe. Two kinds of time-of-flight electron analyzers were employed to examine photoionization very close to threshold and at higher kinetic energies. Partial cross sections and angular distributions have been measured for a number of photoelectron satellites. The shake-off probability has been determined at some inner-shell resonances. 121 refs., 28 figs., 13 tabs.

  13. Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses

    Science.gov (United States)

    Calegari, F.; Ayuso, D.; Trabattoni, A.; Belshaw, L.; De Camillis, S.; Anumula, S.; Frassetto, F.; Poletto, L.; Palacios, A.; Decleva, P.; Greenwood, J. B.; Martín, F.; Nisoli, M.

    2014-10-01

    In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub-4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems.

  14. Analysis of interference in attosecond transient absorption in adiabatic condition

    CERN Document Server

    Dong, Wenpu; Wang, Xiaowei; Zhao, Zengxiu

    2015-01-01

    We simulate the transient absorption of attosecond pulses of infrared laser-dressed atoms by considering a three-level system with the adiabatic approximation. We study the delay-dependent interference features in the transient absorption spectra of helium atoms from the perspective of the coherent interaction processes between the attosecond pulse and the quasi-harmonics, and find that many features of the interference fringes in the absorption spectra of the attosecond pulse can be attributed to the coherence phase difference. And the modulation signals of laser-induced sidebands of the dark state is found related to the dark state with population modulated by the dressing field.

  15. The attosecond regime of impulsive stimulated electronic Raman excitation

    CERN Document Server

    Ware, Matthew R; Cryan, James P; Haxton, Daniel J

    2016-01-01

    We have calculated the resonant and nonresonant contributions to attosecond impulsive stimulated electronic Raman scattering (SERS) in regions of autoionizing transitions. Comparison with Multiconfiguration Time-Dependent Hartree-Fock (MCTDHF) calculations find that attosecond SERS is dominated by continuum transitions and not autoionizing resonances. These results agree quantitatively with a rate equation that includes second-order Raman and first-and second-order photoionization rates. Such rate models can be extended to larger molecular systems. Our results indicate that attosecond SERS transition probabilities may be understood in terms of two-photon generalized cross sections even in the high-intensity limit for extreme ultraviolet wavelengths.

  16. Tomographic reconstruction of circularly polarized high-harmonic fields: 3D attosecond metrology.

    Science.gov (United States)

    Chen, Cong; Tao, Zhensheng; Hernández-García, Carlos; Matyba, Piotr; Carr, Adra; Knut, Ronny; Kfir, Ofer; Zusin, Dimitry; Gentry, Christian; Grychtol, Patrik; Cohen, Oren; Plaja, Luis; Becker, Andreas; Jaron-Becker, Agnieszka; Kapteyn, Henry; Murnane, Margaret

    2016-02-01

    Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date.

  17. Methods of Attosecond X-Ray Pulse Generation

    CERN Document Server

    Zholents, Alexander

    2005-01-01

    Our attitude towards attosecond x-ray pulses has changed dramatically over the past several years. Not long ago x-ray pulses with a duration of a few hundred attoseconds were just science fiction for most of us, but they are already a tool for some researchers in present days. Breakthrough progress in the generation of solitary soft x-ray pulses of attosecond duration has been made by the laser community. Following this lead, people in the free electron laser community have begun to develop new ideas on how to generate attosecond x-ray pulses in the hard x-ray energy range. In this report I will review some of these ideas.

  18. Connecting Lab-Based Attosecond Science with FEL research

    CERN Document Server

    CERN. Geneva

    2011-01-01

    In the last few years laboratory-scale femtosecond laser-based research using XUV light has developed dramatically following the successful development of attosecond laser pulses by means of high-harmonic generation. Using attosecond laser pulses, studies of electron dynamics on the natural timescale that electronic processes occur in atoms, molecules and solids can be contemplated, providing unprecedented insight into the fundamental role that electrons play in photo-induced processes. In my talk I will briefly review the present status of the attosecond science research field in terms of present and foreseen capabilities, and discuss a few recent applications, including a first example of the use of attosecond laser pulses in molecular science. In addition, I will discuss very recent results of experiments where photoionization of dynamically aligned molecules is investigated using a high-harmonics XUV source. Photoionization of aligned molecules becomes all the more interesting if the experiment is perfo...

  19. Making use of x-ray optical effects in photoelectron-, Auger electron-, and x-ray emission spectroscopies: Total reflection, standing-wave excitation, and resonant effects

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S.-H. [IBM Almaden Research Center, San Jose, California 95120 (United States); Gray, A. X. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States); Stanford Institute for Materials and Energy Science, Stanford University and SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Kaiser, A. M. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States); Peter Grunberg Institute, PGI-6, Forschungszentrum Juelich, 52425 Juelich (Germany); Mun, B. S. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Applied Physics, Hanyang University, Ansan, Gyeonggi 426-791 (Korea, Republic of); Sell, B. C. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States); Department of Physics, Otterbein College, Westerville, Ohio 43081 (United States); Kortright, J. B. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Fadley, C. S. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States)

    2013-02-21

    We present a general theoretical methodology and related open-access computer program for carrying out the calculation of photoelectron, Auger electron, and x-ray emission intensities in the presence of several x-ray optical effects, including total reflection at grazing incidence, excitation with standing-waves produced by reflection from synthetic multilayers and at core-level resonance conditions, and the use of variable polarization to produce magnetic circular dichroism. Calculations illustrating all of these effects are presented, including in some cases comparisons to experimental results. Sample types include both semi-infinite flat surfaces and arbitrary multilayer configurations, with interdiffusion/roughness at their interfaces. These x-ray optical effects can significantly alter observed photoelectron, Auger, and x-ray intensities, and in fact lead to several generally useful techniques for enhancing surface and buried-layer sensitivity, including layer-resolved densities of states and depth profiles of element-specific magnetization. The computer program used in this study should thus be useful for a broad range of studies in which x-ray optical effects are involved or are to be exploited in next-generation surface and interface studies of nanoscale systems.

  20. Using "Tender" X-ray Ambient Pressure X-Ray Photoelectron Spectroscopy as A Direct Probe of Solid-Liquid Interface.

    Science.gov (United States)

    Axnanda, Stephanus; Crumlin, Ethan J; Mao, Baohua; Rani, Sana; Chang, Rui; Karlsson, Patrik G; Edwards, Mårten O M; Lundqvist, Måns; Moberg, Robert; Ross, Phil; Hussain, Zahid; Liu, Zhi

    2015-05-07

    We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a "dip &pull" method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, "dip &pull" approach, with a "tender" X-ray synchrotron source (2 keV-7 keV), we are able to access the interface between liquid and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt(2+) and Pt(4+) interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of "tender" AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.

  1. Many-electron effects in photoelectron spectroscopy. [Deviations from Koopman's one-electron model, satellite structure, configuration interaction, mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Martin, R.L.

    1976-06-01

    The deviations from Koopmans' one-electron model of photoionization which lead to satellite structure in the photoelectron spectrum are examined within the formalism of configuration interaction (CI). The mechanisms which contribute to satellite intensity may be classified as continuum state configuration interaction, final ionic state configuration interaction, and initial state configuration interaction. The discussion centers around the last two mechanisms, these being the prime contributors to the satellite intensity well above threshold. Specific examples of theoretical ''spectra'' are presented for the F(1s) region of HF and the 1s region of neon. The agreement between theory and experiment is found to be excellent. In these two instances, initial state configuration interaction contributions increase the satellite intensity and are of nearly equal importance to the final ionic state mixing.

  2. Electronic structures of AlMoO(y)(-) (y = 1-4) determined by photoelectron spectroscopy and density functional theory calculations.

    Science.gov (United States)

    Waller, Sarah E; Mann, Jennifer E; Hossain, Ekram; Troyer, Mary; Jarrold, Caroline C

    2012-07-14

    Vibrationally-resolved photoelectron spectra of AlMoO(y)(-) (y = 1-4) are presented and analyzed in conjunction with density functional theory computational results. The structures determined for the AlMoO(y) anion and neutral clusters suggest ionic bonding between Al(+) and a MoO(y)(-) or MoO(y)(-2) moiety, and point to the relative stability of Mo=O versus Al=O bonds. The highest occupied and partially occupied orbitals in the anions and neutrals can be described as Mo atomic-like orbitals, so while the Mo is in a higher oxidation state than Al, the most energetically accessible electrons are localized on the molybdenum center.

  3. Co/Mo2C mirror as studied by x-ray fluorescence and photoelectron spectroscopies induced by x-ray standing waves

    Science.gov (United States)

    Jonnard, P.; Le Guen, K.; Yuan, Y. Y.; André, J.-M.; Mukherjee, S.; Giglia, A.; Nannarone, S.; Mahne, N.; Wang, Z.-S.; Li, H.-C.; Zhu, J.-T.

    2012-12-01

    We study a periodic Co/Mo2C multilayer prepared by magnetron sputtering. The period is 4.1 nm and the sample is designed to work around 778 eV, i.e. close to the Co 2p3/2 threshold, at a glancing angle of 11°. In this condition, strong x-ray standing waves set up within the sample. In order to probe different depths within the stack, particularly the interfaces, the glancing angle is moved along the first Bragg peak, while, the B 1s, C 1s, Mo 3d or O 1s photoelectron spectra, the Co Lα x-ray spectrum as well as the drain current of the sample are measured. Boron is present in the 3.5 nm B4C capping layer and oxygen is from surface contamination. The photoelectrons bring information from the superficial zone, i.e. the 5 first nm, while the characteristic x-rays probe the whole stack. Clear modulations of the intensity of the studied signals as well as core level shifts are observed when going through the Bragg peak. In order to understand what happens in the multilayer calculations of depth distributions of the electric field and the energy loss by the radiation are made with the IMD and OPAL codes, respectively. The combination of experimental results and theoretical simulations will enable us to determine from which place originate the various signals and to know if some interaction exists between the Co and Mo2C layers.

  4. Electronic structures of WAlO(y) and WAlO(y)(-) (y = 2-4) determined by anion photoelectron spectroscopy and density functional theory calculations.

    Science.gov (United States)

    Mann, Jennifer E; Waller, Sarah E; Jarrold, Caroline Chick

    2012-07-28

    The anion photoelectron spectra of WAlO(y)(-) (y = 2-4) are presented and assigned based on results of density functional theory calculations. The WAlO(2)(-) and WAlO(3)(-) spectra are both broad, with partially resolved vibrational structure. In contrast, the WAlO(4)(-) spectrum features well-resolved vibrational structure with contributions from three modes. There is reasonable agreement between experiment and theory for all oxides, and calculations are in particular validated by the near perfect agreement between the WAlO(4)(-) photoelectron spectrum and a Franck-Condon simulation based on computationally determined spectroscopic parameters. The structures determined from this study suggest strong preferential W-O bond formation, and ionic bonding between Al(+) and WO(y)(-2) for all anions. Neutral species are similarly ionic, with WAlO(2) and WAlO(3) having electronic structure that suggests Al(+) ionically bound to WO(y)(-) and WAlO(4) being described as Al(+2) ionically bound to WO(4)(-2). The doubly-occupied 3sp hybrid orbital localized on the Al center is energetically situated between the bonding O-local molecular orbitals and the anti- or non-bonding W-local molecular orbitals. The structures determined in this study are very similar to structures recently determined for the analogous MoAlO(y)(-)/MoAlO(y) cluster series, with subtle differences found in the electronic structures [S. E. Waller, J. E. Mann, E. Hossain, M. Troyer, and C. C. Jarrold, J. Chem. Phys. 137, 024302 (2012)].

  5. Ticking terahertz wave generation in attoseconds

    CERN Document Server

    Zhang, Dongwen; Meng, Chao; Du, Xiyu; Zhou, Zhaoyan; Zhao, Zengxiu; Yuan, Jianmin

    2012-01-01

    We perform a joint measurement of terahertz waves and high-order harmonics generated from noble atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase-delay of the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft-collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in HHG processes, dominant THz wave generation as well but in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics.

  6. Attosecond clocking of scattering dynamics in dielectrics

    Science.gov (United States)

    Kling, Matthias

    2016-05-01

    In the past few years electronic-device scaling has progressed rapidly and miniaturization has reached physical gate lengths below 100 nm, heralding the age of nanoelectronics. Besides the effort in size scaling of integrated circuits, tremendous progress has recently been made in increasing the switching speed where strong-field-based ``dielectric-electronics'' may push it towards the petahertz frontier. In this contest, the investigation of the electronic collisional dynamics occurring in a dielectric material is of primary importance to fully understand the transport properties of such future devices. Here, we demonstrate attosecond chronoscopy of electron collisions in SiO2. In our experiment, a stream of isolated aerodynamically focused SiO2 nanoparticles of 50 nm diameter was delivered into the laser interaction region. Photoemission is initiated by an isolated 250 as pulse at 35 eV and the electron dynamics is traced by attosecond streaking using a delayed few-cycle laser pulse at 700 nm. Electrons were detected by a kilohertz, single-shot velocity-map imaging spectrometer, permitting to separate frames containing nanoparticle signals from frames containing the response of the reference gas only. We find that the nanoparticle photoemission exhibits a positive temporal shift with respect to the reference. In order to understand the physical origin of the shift we performed semi-classical Monte-Carlo trajectory simulations taking into account the near-field distributions in- and outside the nanoparticles as obtained from Mie theory. The simulations indicate a pronounced dependence of the streaking time shift near the highest measured electron energies on the inelastic scattering time, while elastic scattering only shows a small influence on the streaking time shift for typical dielectric materials. We envision our approach to provide direct time-domain access to inelastic scattering for a wide range of dielectrics.

  7. Probing cation antisite disorder in Gd2 Ti2 O7 pyrochlore by site-specific near-edge x-ray-absorption fine structure and x-ray photoelectron spectroscopy

    Science.gov (United States)

    Nachimuthu, P.; Thevuthasan, S.; Engelhard, M. H.; Weber, W. J.; Shuh, D. K.; Hamdan, N. M.; Mun, B. S.; Adams, E. M.; McCready, D. E.; Shutthanandan, V.; Lindle, D. W.; Balakrishnan, G.; Paul, D. M.; Gullikson, E. M.; Perera, R. C. C.; Lian, J.; Wang, L. M.; Ewing, R. C.

    2004-09-01

    Disorder in Gd2Ti2O7 is investigated by near-edge x-ray-absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS). NEXAFS shows Ti4+ ions occupy octahedral sites with a tetragonal distortion induced by vacant oxygen sites. O1s XPS spectra obtained with a charge neutralization system from Gd2Ti2O7(100) and the Gd2Ti2O7 pyrochlore used by Chen [Phys. Rev. Lett. 88, 105901 (2002)], both yielded a single peak, unlike the previous result on the latter that found two peaks. The current results give no evidence for an anisotropic distribution of Ti and O. The extra features reported in the aforementioned communication resulted from charging effects and incomplete surface cleaning. Thus, a result confirming the direct observation of simultaneous cation-anion antisite disordering and lending credence to the split vacancy model has been clarified.

  8. High-power, narrow-band, high-repetition-rate, 5.9 eV coherent light source using passive optical cavity for laser-based angle-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Omachi, J; Yoshioka, K; Kuwata-Gonokami, M

    2012-10-08

    We demonstrate a scheme for efficient generation of a 5.9 eV coherent light source with an average power of 23 mW, 0.34 meV linewidth, and 73 MHz repetition rate from a Ti: sapphire picosecond mode-locked laser with an output power of 1 W. Second-harmonic light is generated in a passive optical cavity by a BiB(3)O(6) crystal with a conversion efficiency as high as 67%. By focusing the second-harmonic light transmitted from the cavity into a β-BaB(2)O(4) crystal, we obtain fourth-harmonic light at 5.9 eV. This light source offers stable operation for at least a week. We discuss the suitability of the laser light source for high-resolution angle-resolved photoelectron spectroscopy by comparing it with other sources (synchrotron radiation facilities and gas discharge lamp).

  9. Surface and interface analysis of a Roman lead pipe ``fistula'': microchemistry of the soldering at the join, as seen by scanning Auger microscopy and X-ray photoelectron spectroscopy

    Science.gov (United States)

    Paparazzo, Ernesto

    1994-01-01

    Scanning Auger microscopy (SAM) and X-ray photoelectron spectroscopy (XPS) are used to study the surface and interface chemical composition of a Roman lead pipe (fistula). Experimental evidence is provided that the Romans used tin for soldering the join, and the chemical nature of the single elements, e.g. whether in metallic or combined form, is identified. SAM discloses the segregation of the chemical elements with a sub-micron spatial resolution, and large deviations in the quantitative results are found relative to the large-area averaged XPS results. Elemental depth profiles are obtained from all over the body of the pipe: we find that the lead is less oxidized at the join, and this region contains many more hydrocarbon species, which we interpret as deriving from the use of oil for anti-oxidizing purposes. Our experimental findings are consistent with Plinius' report on the lead-tin soldering techniques used in the Roman world.

  10. A study of reversible gamma-induced structural transformations in vitreous Ge23.5Sb11.8S64.7 by high-resolution X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Kovalskiy, Andriy; Jain, Himanshu; Miller, Alfred C; Golovchak, Roman Ya; Shpotyuk, Oleh I

    2006-11-16

    The structural origin of reversible gamma-induced effects in vitreous Ge(23.5)Sb(11.8)S(64.7) has been investigated by high-resolution X-ray photoelectron spectroscopy (XPS). The changes in valence band spectrum from gamma-irradiation suggest a decrease of sulfur lone pair electron concentration accompanied by changes in bonding states of S and Ge. The appearance of additional doublets in the core-level XPS spectra of Ge, Sb, and S atoms for gamma-irradiated sample is described by the formation of over- and under-coordinated charged defect pairs (Ge(3)(-)-S(3)(+)) as a result of radiation treatment. The results verify the switching of Ge-S covalent bonds into S-S bonds as the main microstructural mechanism for gamma-induced optical effects in this glass.

  11. Synchrotron radiation X-ray photoelectron spectroscopy of Ti/Al ohmic contacts to n-type GaN: Key role of Al capping layers in interface scavenging reactions

    Science.gov (United States)

    Nozaki, Mikito; Ito, Joyo; Asahara, Ryohei; Nakazawa, Satoshi; Ishida, Masahiro; Ueda, Tetsuzo; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2016-10-01

    Interface reactions between Ti-based electrodes and n-type GaN epilayers were investigated by synchrotron radiation X-ray photoelectron spectroscopy. Metallic Ga and thin TiN alloys were formed at the interface by subsequently depositing Al capping layers on ultrathin Ti layers even at room temperature. By comparing results from stacked Ti/Al and single Ti electrodes, the essential role of Al capping layers serving as an oxygen-scavenging element to produce reactive Ti underlayers was demonstrated. Further growth of the metallic interlayer during annealing was observed. A strategy for achieving low-resistance ohmic contacts to n-GaN with low-thermal-budget processing is discussed.

  12. The influence of methanol on the chemical state of PtRu anodes in a high-temperature direct methanol fuel cell studied in situ by synchrotron-based near-ambient pressure x-ray photoelectron spectroscopy

    Science.gov (United States)

    Saveleva, Viktoriia A.; Daletou, Maria K.; Savinova, Elena R.

    2017-01-01

    Synchrotron radiation-based near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) has recently become a powerful tool for the investigation of interfacial phenomena in electrochemical power sources such as batteries and fuel cells. Here we present an in situ NAP-XPS study of the anode of a high-temperature direct methanol fuel cell with a phosphoric acid-doped hydrocarbon membrane, which reveals an enhanced flooding of the Pt3Ru anode with phosphoric acid in the presence of methanol. An analysis of the electrode surface composition depending on the cell voltage and on the presence of methanol reveals the strong influence of the latter on the extent of Pt oxidation and on the transformation of Ru into Ru (IV) hydroxide.

  13. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities.

    Science.gov (United States)

    Frassetto, F; Trabattoni, A; Anumula, S; Sansone, G; Calegari, F; Nisoli, M; Poletto, L

    2014-10-01

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10(11) W/cm(2).

  14. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Frassetto, F.; Poletto, L., E-mail: poletto@dei.unipd.it [National Research Council, Institute of Photonics and Nanotechnologies, via Trasea 7, 35131 Padova (Italy); Trabattoni, A.; Anumula, S.; Sansone, G. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); Calegari, F. [National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy); Nisoli, M. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy)

    2014-10-15

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10{sup 11} W/cm{sup 2}.

  15. Electronic and chemical structure of an organic light emitter embedded in an inorganic wide-bandgap semiconductor: Photoelectron spectroscopy of layered and composite structures of Ir(BPA) and ZnSe

    Science.gov (United States)

    Dimamay, Mariel; Mayer, Thomas; Hadziioannou, Georges; Jaegermann, Wolfram

    2015-05-01

    Luminescent organic phases embedded in conductive inorganic matrices are proposed for hybrid organic-inorganic light-emitting diodes. In this configuration, the organic dye acts as the radiative recombination site for charge carriers injected into the inorganic matrix. Our investigation is aimed at finding a material combination where the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the organic dye are situated in between the valence and conduction bands of the inorganic matrix in order to promote electron and hole transfer from the matrix to the dye. Bilayer and composite thin films of zinc selenide (ZnSe) and a red iridium complex (Ir(BPA)) organic light emitter were prepared in situ via UHV thermal evaporation technique. The electronic and atomic structures were studied applying X-ray and ultraviolet photoelectron spectroscopies. The measured energy band alignments for the ZnSe/Ir(BPA) bilayer and ZnSe+Ir(BPA) composite reveal that the HOMO and LUMO of the organic dye are positioned in the ZnSe bandgap. For the initial steps of ZnSe deposition on a dye film to form Ir(BPA)/ZnSe bilayers, zinc atoms intercalate into the dye film leaving behind an excess of selenium at the interface that partly reacts with dye molecules. Photoelectron spectroscopy of the composites shows the same species suggesting a similar mechanism. This mechanism leads to composite films with increased content of amorphous phases in the inorganic matrix, thereby affecting its conductivity, as well as to the presence of nonradiative recombination sites provided by the intercalated Zn atoms.

  16. Electronic and chemical structure of an organic light emitter embedded in an inorganic wide-bandgap semiconductor: Photoelectron spectroscopy of layered and composite structures of Ir(BPA) and ZnSe

    Energy Technology Data Exchange (ETDEWEB)

    Dimamay, Mariel [Institute of Materials Science, Darmstadt University of Technology, Alarich-Weiss-Strasse 2, D-64287 Darmstadt (Germany); Laboratoire de Chimie des Polymères Organiques, CNRS, Université de Bordeaux, UMR 5629-16 Avenue Pey-Berland, 33607 Pessac (France); Mayer, Thomas; Jaegermann, Wolfram [Institute of Materials Science, Darmstadt University of Technology, Alarich-Weiss-Strasse 2, D-64287 Darmstadt (Germany); Hadziioannou, Georges [Laboratoire de Chimie des Polymères Organiques, CNRS, Université de Bordeaux, UMR 5629-16 Avenue Pey-Berland, 33607 Pessac (France)

    2015-05-07

    Luminescent organic phases embedded in conductive inorganic matrices are proposed for hybrid organic-inorganic light-emitting diodes. In this configuration, the organic dye acts as the radiative recombination site for charge carriers injected into the inorganic matrix. Our investigation is aimed at finding a material combination where the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the organic dye are situated in between the valence and conduction bands of the inorganic matrix in order to promote electron and hole transfer from the matrix to the dye. Bilayer and composite thin films of zinc selenide (ZnSe) and a red iridium complex (Ir(BPA)) organic light emitter were prepared in situ via UHV thermal evaporation technique. The electronic and atomic structures were studied applying X-ray and ultraviolet photoelectron spectroscopies. The measured energy band alignments for the ZnSe/Ir(BPA) bilayer and ZnSe+Ir(BPA) composite reveal that the HOMO and LUMO of the organic dye are positioned in the ZnSe bandgap. For the initial steps of ZnSe deposition on a dye film to form Ir(BPA)/ZnSe bilayers, zinc atoms intercalate into the dye film leaving behind an excess of selenium at the interface that partly reacts with dye molecules. Photoelectron spectroscopy of the composites shows the same species suggesting a similar mechanism. This mechanism leads to composite films with increased content of amorphous phases in the inorganic matrix, thereby affecting its conductivity, as well as to the presence of nonradiative recombination sites provided by the intercalated Zn atoms.

  17. Comparison of X-ray photoelectron spectroscopy multiplet splitting of Cr 2p peaks from chromium tris(β-diketonates) with chemical effects

    Energy Technology Data Exchange (ETDEWEB)

    Liu, R.; Conradie, J.; Erasmus, E., E-mail: erasmuse@ufs.ac.za

    2016-01-15

    Graphical abstract: Synopsis and pictogram for Table of contents The Cr 2p{sub 3/2} peaks obtained from X-ray photoelectron spectra (XPS) of a series of chromium(III) β-diketonato complexes were fitted with calculated multiplet peaks. The ratio of the fac and mer isomers obtained from XPS compared very well with the Boltzmann calculated ratio. The electronegativity of the R-groups on the β-diketonato ligand influences the XPS peak positions. - Highlights: • β-diketonato complexes Cr(RCOCHCOR’){sub 3} • Cr 2p{sub 3/2} XPS peaks fitted with calculated multiplet peaks. • Different calculated multiplet peaks fit the Cr 2p{sub 3/2} peak for fac and mer isomers. • XPS peak positions influenced by the electronegativity of the R- and R'-group. - Abstract: X-ray photoelectron spectra (XPS) measurements of a series of chromium(III) β-diketonato complexes of the Cr 2p spectra was fitted with calculated multiplet peaks. The XPS of these Cr(III) complexes did not exhibit fine structure, however, well-defined line shapes could be fitted to the Cr 2p{sub 3/2} envelope. The splitting patterns obtained for the Cr(III) β-diketonato complexes compared well with the multiplet splitting predicted by Gupta and Sen for the free Cr(III) ion. The Cr(III) β-diketonato complexes containing unsymmetrically substituted β-diketonato ligands, which display both the fac and mer isomers, could be fitted with two sets of multiplets and were useful in determining the ratio between the fac and mer isomers, which was compared with the Boltzman calculated ratio obtained from density functional theory energies. The obtained binding energy of the first multiplet splitting peak of the Cr 2p{sub 3/2} envelope was found to be dependent on the combined Gordy group electronegativity of the R-groups substituted on the β-diketonato ligand (RCOCHCOR′){sup −}.

  18. Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility.

    Science.gov (United States)

    Oura, Masaki; Wagai, Tatsuya; Chainani, Ashish; Miyawaki, Jun; Sato, Hiromi; Matsunami, Masaharu; Eguchi, Ritsuko; Kiss, Takayuki; Yamaguchi, Takashi; Nakatani, Yasuhiro; Togashi, Tadashi; Katayama, Tetsuo; Ogawa, Kanade; Yabashi, Makina; Tanaka, Yoshihito; Kohmura, Yoshiki; Tamasaku, Kenji; Shin, Shik; Ishikawa, Tetsuya

    2014-01-01

    In order to utilize high-brilliance photon sources, such as X-ray free-electron lasers (XFELs), for advanced time-resolved photoelectron spectroscopy (TR-PES), a single-shot CCD-based data acquisition system combined with a high-resolution hemispherical electron energy analyzer has been developed. The system's design enables it to be controlled by an external trigger signal for single-shot pump-probe-type TR-PES. The basic performance of the system is demonstrated with an offline test, followed by online core-level photoelectron and Auger electron spectroscopy in 'single-shot image', 'shot-to-shot image (image-to-image storage or block storage)' and `shot-to-shot sweep' modes at soft X-ray undulator beamline BL17SU of SPring-8. In the offline test the typical repetition rate for image-to-image storage mode has been confirmed to be about 15 Hz using a conventional pulse-generator. The function for correcting the shot-to-shot intensity fluctuations of the exciting photon beam, an important requirement for the TR-PES experiments at FEL sources, has been successfully tested at BL17SU by measuring Au 4f photoelectrons with intentionally controlled photon flux. The system has also been applied to hard X-ray PES (HAXPES) in `ordinary sweep' mode as well as shot-to-shot image mode at the 27 m-long undulator beamline BL19LXU of SPring-8 and also at the SACLA XFEL facility. The XFEL-induced Ti 1s core-level spectrum of La-doped SrTiO3 is reported as a function of incident power density. The Ti 1s core-level spectrum obtained at low power density is consistent with the spectrum obtained using the synchrotron source. At high power densities the Ti 1s core-level spectra show space-charge effects which are analysed using a known mean-field model for ultrafast electron packet propagation. The results successfully confirm the capability of the present data acquisition system for carrying out the core-level HAXPES studies of condensed matter induced by the XFEL.

  19. Threshold photoelectron spectroscopy of unstable N-containing compounds: Resolution of ΔK subbands in HNCO{sup +} and vibrational resolution in NCO{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Holzmeier, Fabian; Lang, Melanie; Fischer, Ingo, E-mail: ingo.fischer@uni-wuerzburg.de [Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg (Germany); Tang, Xiaofeng [Synchrotron SOLEIL, l’Orme des Merisiers, Saint Aubin BP 48, F-91192 Gif sur Yvette Cedex (France); Cunha de Miranda, Barbara; Romanzin, Claire; Alcaraz, Christian [Laboratoire de Chimie-Physique, UMR 8000 CNRS and Université Paris-Sud 11, F-91405 Orsay Cedex (France); Hemberger, Patrick [Molecular Dynamics Group, Paul Scherrer Institute (PSI), CH-5232 Villigen (Switzerland)

    2015-05-14

    The threshold photoelectron spectra (TPES) of two unstable nitrogen-containing species, HNCO and NCO, were recorded utilizing vacuum ultraviolet synchrotron radiation. Both are intermediates in combustion processes and play a role in the removal of nitrogen oxides from exhaust gases. The rovibronic structure of the first band in the TPES of HNCO{sup +} was analyzed within the framework of an orbital ionization model, and the resolved structure of the origin band was assigned to ΔK subbands. An ionization energy of 11.602 ± 0.005 eV was determined and the vibrational structure of the cationic ground state was analyzed by a Franck-Condon fit. Low lying electronically excited states of HNCO{sup +} were also observed. In a second series of experiments, the NCO radical was generated by flash pyrolysis from chlorine isocyanate. The ionization energy to the X{sup +} {sup 3}Σ{sup −} ground state was determined to be 11.76 ± 0.02 eV, while for the a{sup +1}Δ state, a value of 12.93 ± 0.02 eV was obtained. Vibrational structure was observed for both states, and bands were assigned by Franck-Condon simulations.

  20. Surface and subsurface oxidation of Mo2C/Mo(100): low-energy ion-scattering, auger electron, angle-resolved X-ray photoelectron, and mass spectroscopy studies.

    Science.gov (United States)

    Ovári, László; Kiss, János; Farkas, Arnold P; Solymosi, Frigyes

    2005-03-17

    The interaction of oxygen with a carburized Mo(100) surface was investigated at different temperatures (300-1000 K). The different information depths of low-energy ion-scattering (LEIS) spectroscopy, with topmost layer sensitivity, Auger electron spectroscopy (AES), and angle-resolved X-ray photoelectron spectroscopy (ARXPS) allowed us to discriminate between reactions on the topmost layer and subsurface transformations. According to ARXPS measurements, a carbide overlayer was prepared by the high-temperature decomposition of C(2)H(4) on Mo(100), and the carbon distribution proved to be homogeneous with a Mo(2)C stoichiometry down to the information depth of XPS. O(2) adsorbs dissociatively on the carbide layer at room temperature. One part of the chemisorbed oxygen is bound to both C and Mo sites, indicated by LEIS. Another fraction of oxygen atoms probably resides in the hollow sites not occupied by C. The removal of C from the outermost layer by O(2), in the form of CO, detected by mass spectroscopy (MS), was observed at 500-600 K. The carbon-depleted first layer is able to adsorb more oxygen compared to the Mo(2)C/Mo(100) surface. Applying higher doses of O(2) at 800 K results in the inward diffusion of O and the partial oxidation of Mo atoms. This process, however, is not accompanied by the removal of C from subsurface sites. The depletion of C from the bulk starts only at 900 K (as shown by MS, AES, and XPS), very probably by the diffusion of C to the surface followed by its reaction with oxygen. At T(ads) = 1000 K, the carbon content of the sample, down to the information depth of XPS, decreased further, accompanied by the attenuation of the C concentration gradient and a substantially decreased amount of oxygen.

  1. Attosecond Hard X-ray Free Electron Laser

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar

    2013-03-01

    Full Text Available In this paper, several schemes of soft X-ray and hard X-ray free electron lasers (XFEL and their progress are reviewed. Self-amplified spontaneous emission (SASE schemes, the high gain harmonic generation (HGHG scheme and various enhancement schemes through seeding and beam manipulations are discussed, especially in view of the generation of attosecond X-ray pulses. Our recent work on the generation of attosecond hard X-ray pulses is also discussed. In our study, the enhanced SASE scheme is utilized, using electron beam parameters of an XFEL under construction at Pohang Accelerator Laboratory (PAL. Laser, chicane and electron beam parameters are optimized to generate an isolated attosecond hard X-ray pulse at 0.1 nm (12.4 keV. The simulations show that the manipulation of electron energy beam profile may lead to the generation of an isolated attosecond hard X-ray of 150 attosecond pulse at 0.1 nm.

  2. The Renner-Teller effect in HCCCl{sup +}(X{sup ~2}Π) studied by zero-kinetic energy photoelectron spectroscopy and ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Wei; Dai, Zuyang; Wang, Jia; Mo, Yuxiang, E-mail: ymo@mail.tsinghua.edu.cn [Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China)

    2015-05-21

    The spin-vibronic energy levels of the chloroacetylene cation up to 4000 cm{sup −1} above the ground state have been measured using the one-photon zero-kinetic energy photoelectron spectroscopic method. The spin-vibronic energy levels have also been calculated using a diabatic model, in which the potential energy surfaces are expressed by expansions of internal coordinates, and the Hamiltonian matrix equation is solved using a variational method with harmonic basis functions. The calculated spin-vibronic energy levels are in good agreement with the experimental data. The Renner-Teller (RT) parameters describing the vibronic coupling for the H—C≡C bending mode (ε{sub 4}), Cl—C≡C bending mode (ε{sub 5}), the cross-mode vibronic coupling (ε{sub 45}) of the two bending vibrations, and their vibrational frequencies (ω{sub 4} and ω{sub 5}) have also been determined using an effective Hamiltonian matrix treatment. In comparison with the spin-orbit interaction, the RT effect in the H—C≡C bending (ε{sub 4}) mode is strong, while the RT effect in the Cl—C≡C bending mode is weak. There is a strong cross-mode vibronic coupling of the two bending vibrations, which may be due to a vibronic resonance between the two bending vibrations. The spin-orbit energy splitting of the ground state has been determined for the first time and is found to be 209 ± 2 cm{sup −1}.

  3. Electronic structure and optical properties of Cs2HgCl4: DFT calculations and X-ray photoelectron spectroscopy measurements

    Science.gov (United States)

    Lavrentyev, A. A.; Gabrelian, B. V.; Vu, V. T.; Parasyuk, O. V.; Fedorchuk, A. O.; Khyzhun, O. Y.

    2016-10-01

    A high-quality single crystal of cesium mercury tetrabromide, Cs2HgCl4, was synthesized by using the vertical Bridgman-Stockbarger method and its electronic structure was studied from both experimental and theoretical viewpoints. In particular, X-ray photoelectron spectra were measured for both pristine and Ar+ ion-bombarded Cs2HgCl4 single crystal surfaces. The present XPS measurements indicate that the Cs2HgCl4 single crystal surface is sensitive with respect to Ar+ ion-bombardment: such a treatment changes substantially its elemental stoichiometry. With the aim of exploring total and partial densities of states within the valence band and conduction band regions of the Cs2HgCl4 compound, band-structure calculations based on density functional theory (DFT) using the augmented plane wave + local orbitals (APW + lo) method as incorporated within the WIEN2k package are performed. The calculations indicate that the Cl 3p states are the principal contributors in the upper portion of the valence band, while the Hg 5d and Cs 5p states dominate in its lower portion. In addition, the calculations allow for concluding that the unoccupied Cl p and Hg s states are the main contributors to the bottom of the conduction band. Furthermore, main optical characteristics of Cs2HgCl4, namely dispersion of the absorption coefficient, real and imaginary parts of dielectric function, electron energy-loss spectrum, refractive index, extinction coefficient and optical reflectivity, are elucidated based on the DFT calculations.

  4. Determination of the limit of detection by X-ray photoelectron spectroscopy for As, Zn and Pb oxides in SiO2 matrix as model systems for environmental investigations

    Science.gov (United States)

    Atzei, Davide; Elsener, Bernhard; Fantauzzi, Marzia; Brundu, Fabio; Rossi, Antonella

    2016-07-01

    In this work the detection limits of arsenic, zinc and lead in silica matrix by X-ray photoelectron spectroscopy (XPS) analysis were evaluated. These elements were selected since they are particularly relevant in environmental investigations. Pure oxides and several binary mixtures with silica at different concentrations of As (III), Zn (II) and Pb (II) oxides obtained by ball milling were analysed by XPS. Inductive-coupled plasma optical emission spectroscopy (ICP-OES) was also exploited for determining their bulk concentration. The linear response of XPS intensity vs weighed (at%) was confirmed. Three different models were here applied to estimate the limit of detection (LOD) of arsenic, zinc and lead and the results were in good agreement. Under the experimental conditions here adopted, the calculated LODs (at%) of arsenic, zinc, and lead as pure oxides and in silica matrix were found to range between 0.1 and 0.3, between 0.04 and 0.1 and between 0.03 and 0.04 respectively.

  5. Enhanced corrosion resistance of mild steel in normal sulfuric acid medium by 2,5-bis(n-thienyl)-1,3,4-thiadiazoles: Electrochemical, X-ray photoelectron spectroscopy and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Lebrini, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF-LSPES UMR-CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Lagrenee, M. [Unite de Catalyse et de Chimie du Solide, UMR-CNRS 8181, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Traisnel, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF-LSPES UMR-CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Gengembre, L. [Unite de Catalyse et de Chimie du Solide, UMR-CNRS 8181, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Vezin, H. [Laboratoire de Chimie Organique et Macromoleculaire, UMR-CNRS 8009, USTL Bat C4, F-59655 Villeneuve d' Ascq Cedex (France); Bentiss, F. [Laboratoire de Chimie de Coordination et d' Analytique, Faculte des Sciences, Universite Chouaib Doukkali, BP 20, M-24000 El Jadida (Morocco)], E-mail: f.bentiss@pop.ensc-lille.fr

    2007-09-30

    The inhibitive action of some thiadiazole derivatives, namely 2,5-bis(2-thienyl)-1,3,4-thiadiazole (2-TTH) and 2,5-bis(3-thienyl)-1,3,4-thiadiazole (3-TTH) against the corrosion of mild steel in 0.5 M H{sub 2}SO{sub 4} solution has been investigated using weight loss measurements, Tafel polarisation and electrochemical impedance spectroscopy (EIS) techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution. The protection efficiency increased with increasing inhibitors concentration and the ability of the molecule to adsorb on the steel surface was dependent on the position of the sulphur atom on the thienyl substituent. Inhibition efficiency values obtained from various methods employed were in reasonable agreement. Potentiodynamic polarisation studies clearly showed that 2-TTH and 3-TTH acted as mixed inhibitors. Adsorption of these inhibitors on steel surface obeyed to Langmuir adsorption isotherm. X-ray photoelectron spectroscopy and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal sulphuric solution by n-TTH is due to the formation of a chemisorbed film on the steel surface. Molecular modelling was used to gain some insight, about structural and electronic effects in relation to the inhibiting efficiencies.

  6. Fullerene photoemission time delay explores molecular cavity in attoseconds

    CERN Document Server

    Magrakvelidze, Maia; Dixit, Gopal; Madjet, Mohamed El-Amine; Chakraborty, Himadri S

    2014-01-01

    Time-resolved photoelectron spectroscopy can probe interference oscillations in C60 valence emissions that produce series of minima whose energy separation depends on the molecular size. We show that the quantum phase associated with these minima exhibits rapid variations due to electron correlations, causing rich structures in the photoemission time delay. These findings provide a way to utilize temporal information to access the fullerene cavity size, that is making the time to "see" the space, and can be generalized to photoemissions from clusters and nanostructures.

  7. Charge Migration in Phenylalanine Initiated by Attosecond Pulses

    Science.gov (United States)

    Greenwood, Jason; Trabattoni, Andrea; Ayuso, David; Belshaw, Louise; de Camillis, Simone; Anumula, Sunil; Frassetto, Fabio; Poletto, Luca; Palacios, Alicia; Declava, Piero; Martin, Fernando; Calegari, Francesca; Nisoli, Mauro

    2015-05-01

    In the past few years attosecond techniques have been implemented for the investigation of ultrafast dynamics in molecules. The generation of isolated attosecond pulses characterized by a relatively high photon flux has opened up new possibilities in the study of molecular dynamics. We report on experimental and theoretical results of ultrafast charge dynamics in a biochemically relevant molecule, namely, the amino acid phenylalanine. The data represent the first experimental demonstration of the generation and observation of a charge migration process in a complex molecule, where electron dynamics precede nuclear motion. The application of attosecond technology to the investigation of electron dynamics in biologically relevant molecules represents a multidisciplinary work, which can open new research frontiers: those in which few femtosecond and even sub-femtosecond electron processes determine the fate of biomolecules.

  8. Attosecond experiments on plasmonic nanostructures principles and experiments

    CERN Document Server

    Schötz, Johannes

    2016-01-01

    Johannes Schötz presents the first measurements of optical electro-magnetic near-fields around nanostructures with subcycle-resolution. The ability to measure and understand light-matter interactions on the nanoscale is an important component for the development of light-wave-electronics, the control and steering of electron dynamics with the frequency of light, which promises a speed-up by several orders of magnitude compared to conventional electronics. The experiments presented here on metallic nanotips, widely used in experiments and applications, do not only demonstrate the feasibility of attosecond streaking as a unique tool for fundamental studies of ultrafast nanophotonics but also represent a first important step towards this goal. Contents Electron Scattering in Solids Attosecond Streaking from Metal Nanotips Target Groups Lecturers and students of physics, especially in the area of nanophotonics and attosecond physics About the Author Johannes Schötz received his Master's degree in physics and cu...

  9. Giant half-cycle attosecond pulses

    CERN Document Server

    Wu, H -C

    2011-01-01

    Half-cycle picosecond pulses have been produced from thin photo-conductors, when applying an electric field across the surface and switching on conduction by a short laser pulse. Then the transverse current in the wafer plane emits half-cycle pulses in normal direction, and pulses of 500 fs duration and 1e6 V/m peak electric field have been observed. Here we show that single half-cycle pulses of 50 as duration and up to 1e13 V/m can be produced when irradiating a double foil target by intense few-cycle laser pulses. Focused onto an ultra-thin foil, all electrons are blown out, forming a uniform sheet of relativistic electrons. A second layer, placed at some distance behind, reflects the drive beam, but lets electrons pass straight. Under oblique incidence, beam reflection provides the transverse current, which emits intense half-cycle pulses. Such a pulse may completely ionize even heavier atoms. New types of attosecond pump-probe experiments will become possible.

  10. Maximum information photoelectron metrology

    CERN Document Server

    Hockett, P; Wollenhaupt, M; Baumert, T

    2015-01-01

    Photoelectron interferograms, manifested in photoelectron angular distributions (PADs), are a high-information, coherent observable. In order to obtain the maximum information from angle-resolved photoionization experiments it is desirable to record the full, 3D, photoelectron momentum distribution. Here we apply tomographic reconstruction techniques to obtain such 3D distributions from multiphoton ionization of potassium atoms, and fully analyse the energy and angular content of the 3D data. The PADs obtained as a function of energy indicate good agreement with previous 2D data and detailed analysis [Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)] over the main spectral features, but also indicate unexpected symmetry-breaking in certain regions of momentum space, thus revealing additional continuum interferences which cannot otherwise be observed. These observations reflect the presence of additional ionization pathways and, most generally, illustrate the power of maximum information measurements of th...

  11. Isolated Attosecond Pulses using a Detuned Second-harmonic Field

    Energy Technology Data Exchange (ETDEWEB)

    Merdji, Hamed; /Saclay /SLAC, PULSE; Auguste, Thierry; Boutu, Willem; Caumes, J.-Pascal; Carre, Bertrand; /Saclay; Pfeifer, Thomas; Jullien, Aurelie; Neumark, Daniel M.; Leone, Stephen R.; /UC, Berkeley /LBL, Berkeley

    2007-11-07

    Calculations are presented for the generation of an isolated attosecond pulse in a multicycle two-color strong-field regime. We show that the recollision of the electron wave packet can be confined to half an optical cycle using pulses of up to 40 fs in duration. The scheme is proven to be efficient using two intense beams, one producing a strong field at {omega} and the other a strong field detuned from 2{omega}. The slight detuning {delta}{omega} of the second harmonic is used to break the symmetry of the electric field over many optical cycles and provides a coherent control for the formation of an isolated attosecond pulse.

  12. Band alignment of atomic layer deposited MgO/Zn{sub 0.8}Al{sub 0.2}O heterointerface determined by charge corrected X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Baojun, E-mail: yanbj@ihep.ac.cn [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing P. O. Box 100049 (China); Liu, Shulin [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing P. O. Box 100049 (China); Yang, Yuzhen [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing P. O. Box 100049 (China); Department of Physics, Nanjing University, Nanjing P. O. Box 210093 (China); Heng, Yuekun [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics of Chinese Academy of Sciences, Beijing P. O. Box 100049 (China)

    2016-05-15

    Highlights: • Band alignment of MgO/Zn{sub 0.8}Al{sub 0.2}O heterojunction were investigated systematically using charge corrected X-ray photoelectron spectroscopy. • Differential charging phenomenon is observed in determination VBOs of insulator/semiconductor heterojunction. • Valence and conduction band offsets have been determined to be 0.72 ± 0.11 eV and 3.26 ± 0.11 eV, respectively, with a type-II band line-up. - Abstract: Pure magnesium (MgO) and zinc oxide doped with aluminum oxide (Zn{sub 0.8}Al{sub 0.2}O) were prepared via atomic layer deposition. We have studied the structure and band gap of bulk Zn{sub 0.8}Al{sub 0.2}O material by X-ray diffractometer (XRD) and Tauc method, and the band offsets and alignment of atomic layer deposited MgO/Zn{sub 0.8}Al{sub 0.2}O heterointerface were investigated systematically using X-ray photoelectron spectroscopy (XPS) in this study. Different methodologies, such as neutralizing electron gun, the use of C 1s peak recalibration and zero charging method, were applied to recover the actual position of the core levels in insulator materials which were easily influenced by differential charging phenomena. Schematic band alignment diagram, valence band offset (ΔE{sub V}) and conduction band offset (ΔE{sub C}) for the interface of the MgO/Zn{sub 0.8}Al{sub 0.2}O heterostructure have been constructed. An accurate value of ΔE{sub V} = 0.72 ± 0.11 eV was obtained from various combinations of core levels of heterojunction with varied MgO thickness. Given the experimental band gaps of 7.83 eV for MgO and 5.29 eV for Zn{sub 0.8}Al{sub 0.2}O, a type-II heterojunction with a ΔE{sub C} of 3.26 ± 0.11 eV was found. Band offsets and alignment studies of these heterojunctions are important for gaining deep consideration to the design of various optoelectronic devices based on such heterointerface.

  13. Global nonresonant vibrational-photoelectron coupling in molecular photoionization

    Science.gov (United States)

    Poliakoff, Erwin; Das, Aloke; Hardy, David; Bozek, John; Aguilar, Alex; Lucchese, Robert

    2009-05-01

    Using photoelectron spectroscopy and Schwinger variational scattering theory, we have investigated the coupling between vibrational motion and the exiting photoelectron over extended ranges of photoelectron kinetic energy. Photoelectron spectroscopy is performed with vibrational resolution over uncommonly large ranges of energy (ca. 200 eV). We find clear and significant changes in vibrational branching ratios as a function of photon energy, in direct contradiction to predictions of the Franck-Condon principle. While it is well known that resonances lead to coupling between electronic and vibrational degrees of freedom, nonresonant mechanisms that result in such coupling are not expected or well-documented. Photoelectron spectra are presented for several electronic states of N2^+, CO^+, and NO^+, and we find that valence isoelectronic channels behave very differently, which is also surprising. Theoretical results indicate that Cooper minima are the underlying cause of these effects, and we are currently working to understand the reasons for the sensitivity of the Cooper minima on bond length.

  14. Investigation of Cu-poor and Cu-rich Cu(In,Ga)Se{sub 2}/CdS interfaces using hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ümsür, B., E-mail: buenyamin.uemsuer@helmholtz-berlin.de [Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Calvet, W.; Höpfner, B.; Steigert, A.; Lauermann, I.; Gorgoi, M.; Prietzel, K.; Navirian, H.A.; Kaufmann, C.A.; Unold, T. [Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Lux-Steiner, M. Ch. [Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Freie Universität Berlin, Department of Physics, Arnimallee 14, D-14195 Berlin (Germany)

    2015-05-01

    Cu-poor and Cu-rich Cu(In,Ga)Se{sub 2} (CIGSe) absorbers were used as substrates for the chemical bath deposition of ultrathin CdS buffer layers in the thickness range of a few nanometers in order to make the CIGSe/CdS interface accessible by hard X-ray photo-emission spectroscopy. The composition of both, the absorber and the buffer layer as well as the energetics of the interface was investigated at room temperature and after heating the samples to elevated temperatures (200 °C, 300 °C and 400 °C). It was found that the amount of Cd after the heating treatment depends on the near surface composition of the CIGSe absorber. No Cd was detected on the Cu-poor surface after the 400 °C treatment due to its diffusion into the CIGSe layer. In contrast, Cd was still present on the Cu-rich surface after the same treatment at 400 °C. - Highlights: • Cd diffusion into Cu(In,Ga)Se{sub 2} (CIGSe) absorber is investigated. • Cu-poor and Cu-rich CIGSe samples are compared. • Cd diffusion into CIGSe is found to be dependent on the surface composition of CIGSe.

  15. A study of the Fe-based superconductor SmFeAsO{sub 1-x}F{sub x} by x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y; Chen, Y L; Cui, Y J; Cheng, C H; Zhao, Y [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang, H [Department of Physics, Peking University, Beijing 100871 (China)], E-mail: yzhao@swjtu.edu.cn

    2009-01-15

    The electronic structure of the Fe-based superconductor SmFeAsO{sub 1-x}F{sub x} (x = 0 and 0.2) is studied with x-ray photoemission spectroscopy (XPS) through comparing the band structures of the nonsuperconducting parent material SmFeAsO and the superconducting SmFeAsO{sub 0.8}F{sub 0.2} (T{sub c} = 52.5 K). A small peak centered at 0.2 eV below the Fermi level, E{sub F}, in the valence band is observed in the parent material SmFeAsO, which is due to the low-spin state of the Fe 3d electrons. With fluorine doping, the peak at 0.2 eV disappears and a broad plateau forms near the Fermi level; in the meantime, the density of states at E{sub F} is slightly suppressed. The O 1s and Sm 3d core levels shift towards high energy by {approx}0.55 eV with fluorine doping, but in a sharp comparison, the Fe 2p and As 3d core levels do not shift significantly (the binding energy shift is less than 0.01 eV). It is deduced from the core-level shifts that the Fermi level of the system moves up by 0.55 eV by fluorine doping.

  16. X-ray diffraction and photoelectron spectroscopy studies of MoO 2 as catalyst for the partial oxidation of isooctane

    Science.gov (United States)

    Marin-Flores, Oscar; Scudiero, L.; Ha, Su

    2009-08-01

    X-ray diffraction (XRD), X-ray photoemission (XPS) as well as ultraviolet photoemission (UPS) spectroscopy experiments on MoO 2 powders were carried out to examine the bulk, the core level energies, and the electronic structure of MoO 2 samples that were employed as catalysts for the partial oxidation of isooctane. Five fresh 0.5-g MoO 2 samples were exposed for 0, 0.5, 9, 20, and 43 h to identical reforming environments and their spent samples were analyzed using the techniques mentioned above. Our results indicate the rapid appearance of an intermediate Mo phase with a binding energy of 228.5 eV and whose concentration progressively increases with time. The oxidation state for this new phase was graphically estimated to approximately +2.6 and assigned to the compound Mo 2O 3, which forms on the catalyst surface as a result of its exposure to the reforming environment. The electronic structure probed by UPS reveals two bands, one at 1.62 eV and another at 0.55 eV below the Fermi level, that decrease with the increasing time on stream. These results correlate very well with the drop in the catalytic performance of MoO 2 for the partial oxidation of isooctane and with the decline in the concentration of dioxide (Mo 4+) detected not only on the catalyst surface, but also in the bulk structure, as confirmed by our XRD analysis.

  17. Laser spectroscopy

    CERN Document Server

    Demtröder, Wolfgang

    2008-01-01

    Keeping abreast of the latest techniques and applications, this new edition of the standard reference and graduate text on laser spectroscopy has been completely revised and expanded. While the general concept is unchanged, the new edition features a broad array of new material, e.g., frequency doubling in external cavities, reliable cw-parametric oscillators, tunable narrow-band UV sources, more sensitive detection techniques, tunable femtosecond and sub-femtosecond lasers (X-ray region and the attosecond range), control of atomic and molecular excitations, frequency combs able to synchronize independent femtosecond lasers, coherent matter waves, and still more applications in chemical analysis, medical diagnostics, and engineering.

  18. 高能阿秒脉冲聚焦及光谱分析复合系统设计%Design of a combined system for focusing and spectrum-analyzing of high energy attosecond pulse

    Institute of Scientific and Technical Information of China (English)

    王超; 王兴; 田进寿; 卢裕; 曹希斌; 王俊锋; 徐向晏; 温文龙

    2014-01-01

    为了减小阿秒脉冲聚焦反射过程的能量损失、降低阿秒脉冲测量过程中由聚焦像差引起的测量误差以及提高阿秒光脉冲光谱分析监测的可操作性,采用各环节性能分别优化的方法,设计了一种高能阿秒光脉冲聚焦及光谱分析复合系统,聚焦及光谱分析元件分别采用镀金掠入射型超环面镜和掠入射型凹面聚焦光栅,并给出了其具体结构和特性参量。结果表明,此系统适用于以短脉宽、高能量阿秒脉冲为新型探针的阿秒光谱学研究。%For reducing attosecond pulses energy loss in the focusing reflection process and measurement error caused by attosecond pulse focusing aberration measurement , as well as improving the operability of attosecond pulse spectroscopy monitoring , a combined focusing and spectrum-analysis system for attosecond pulse was designed through step-by-step performance optimization .The structure and characteristic parameters were given in detail .The focusing and spectrum-analyzing components are gold-coated grazing incidence toroidal mirror and grazing incidence concave focusing grating , respectively.The proposed system can find application in research platform of attosecond spectroscopy using high energy short attosecond pulse as basic probe tool .

  19. Surface sites on Pt-CeO2 mixed oxide catalysts probed by CO adsorption: a synchrotron radiation photoelectron spectroscopy study.

    Science.gov (United States)

    Neitzel, Armin; Lykhach, Yaroslava; Skála, Tomáš; Tsud, Nataliya; Vorokhta, Mykhailo; Mazur, Daniel; Prince, Kevin C; Matolín, Vladimír; Libuda, Jörg

    2014-12-07

    By means of synchrotron radiation photoemission spectroscopy, we have investigated Pt-CeO2 mixed oxide films prepared on CeO2(111)/Cu(111). Using CO molecules as a probe, we associate the corresponding surface species with specific surface sites. This allows us to identify the changes in the composition and morphology of Pt-CeO2 mixed oxide films caused by annealing in an ultrahigh vacuum. Specifically, two peaks in C 1s spectra at 289.4 and 291.2 eV, associated with tridentate and bidentate carbonate species, are formed on the nanostructured stoichiometric CeO2 film. The peak at 290.5-291.0 eV in the C 1s spectra indicates the onset of restructuring, i.e. coarsening, of the Pt-CeO2 film. This peak is associated with a carbonate species formed near an oxygen vacancy. The onset of cerium oxide reduction is indicated by the peak at 287.8-288.0 eV associated with carbonite species formed near Ce(3+) cations. The development of surface species on the Pt-CeO2 mixed oxides suggests that restructuring of the films occurs above 300 K irrespective of Pt loadings. We do not find any adsorbed CO species associated with Pt(4+) or Pt(2+). The onset of Pt(2+) reduction is indicated by the peak at 286.9 eV in the C 1s spectra due to CO adsorption on metallic Pt particles. The thermal stability of Pt(2+) in Pt-CeO2 mixed oxide depends on Pt loading. We find excellent stability of Pt(2+) for 12% Pt content in the CeO2 film, whereas at a Pt concentration of 25% in the CeO2 film, a large fraction of the Pt(2+) is converted into metallic Pt particles above 300 K.

  20. Single 100-terawatt attosecond X-ray light pulse generation

    CERN Document Server

    Xu, X R; Zhang, Y X; Lu, H Y; Zhang, H; Dromey, B; Zhu, S P; Zhou, C T; Zepf, M; He, X T

    2016-01-01

    The birth of attosecond light sources is expected to inspire a breakthrough in ultrafast optics, which may extend human real-time measurement and control techniques into atomic-scale electronic dynamics. For applications, it is essential to obtain a single attosecond pulse of high intensity, large photon energy and short duration. Here we show that single 100-terawatt attosecond X-ray light pulse with intensity ${1\\times10^{21}}\\textrm{W}/\\textrm{cm}^{{ 2}}$ and duration ${7.9} \\textrm{as}$ can be produced by intense laser irradiation on a capacitor-nanofoil target composed of two separate nanofoils. In the interaction, a strong electrostatic potential develops between two nanofoils, which drags electrons out of the second foil and piles them up in vacuum, forming an ultradense relativistic electron nanobunch. This nanobunch exists in only half a laser cycle and smears out in others, resulting in coherent synchrotron emission of a single pulse. Such an unprecedentedly giant attosecond X-ray pulse may bring us...