WorldWideScience

Sample records for attosecond photoelectron spectroscopy

  1. Attosecond angle-resolved photoelectron spectroscopy

    International Nuclear Information System (INIS)

    We report experiments on the characterization of a train of attosecond pulses obtained by high-harmonic generation, using mixed-color (XUV+IR) atomic two-photon ionization and electron detection on a velocity map imaging detector. We demonstrate that the relative phase of the harmonics is encoded both in the photoelectron yield and the angular distribution as a function of XUV-IR time delay, thus making the technique suitable for the detection of single attosecond pulses. The timing of the attosecond pulse with respect to the field oscillation of the driving laser critically depends on the target gas used to generate the harmonics

  2. 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.

  3. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Science.gov (United States)

    Jordan, I.; Huppert, M.; Brown, M. A.; van Bokhoven, J. A.; Wörner, H. J.

    2015-12-01

    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.

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

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    an analytical model based on an approximate solution to Boltzmann's transport equation to account for the amount and energy distribution of these secondary electrons. Our theory is in good agreement with the electron spectrum found in a recent attosecond streaking experiment. To suppress the......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...

  5. 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......We study the influence of polarization effects in streaking by combined atto- and femtosecond pulses. The polarization-induced terms alter the streaking spectrum. The conventional streaking spectrum, which maps to the vector potential of the femtosecond pulse, is modified by a contribution...

  6. Attosecond photoelectron spectroscopy of electron transport in solids

    International Nuclear Information System (INIS)

    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

  7. 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

  8. 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.

  9. Monitoring the Birth of an Electronic Wavepacket in a Neutral Molecule with Attosecond Time-Resolved Photoelectron Spectroscopy

    CERN Document Server

    Perveaux, Aurelie; Gatti, Fabien; Halasz, Gabor; Vibok, Agnes; Lasorne, Benjamin

    2014-01-01

    Numerical simulations are presented to validate the possible use of cutting-edge attosecond time- resolved photoelectron spectroscopy to observe in real time the creation of an electronic wavepacket and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds.

  10. Probing dielectric-response effects with attosecond time-resolved streaked photoelectron spectroscopy of metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C.-H.; Thumm, U. [Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

    2011-12-15

    The release of conduction-band electrons from a metal surface by a subfemtosecond extreme ultraviolet (XUV) pulse and their propagation through the solid provoke a dielectric response in the solid that acts back on the photoelectron wave packet. We calculated the (wake) potential associated with this photoelectron self-interaction in terms of bulk and surface plasmon excitations and show that it induces a considerable, XUV-frequency-dependent temporal shift in laser-streaked XUV photoemission spectra, suggesting the observation of the ultrafast solid-state dielectric response in contemporary streaked photoemission experiments.

  11. Attosecond dynamics of nano-localized fields probed by photoelectron spectroscopy

    OpenAIRE

    Süßmann, Frederik

    2013-01-01

    This work focuses on the interaction of few-cycle laser pulses with nanosystems. Special emphasis is placed on the spatio-temporal evolution of the induced near-fields. Measurements on carrier-envelope-phase (CEP) controlled photoemission from isolated SiO2 nanospheres are taken by single-shot velocity map imaging (VMI) combined with CEP tagging. The obtained photoelectron spectra show a pronounced dependence on the CEP and extend to unexpectedly high energies. Comparison with numerical simu...

  12. Attosecond Quantum-Beat Spectroscopy in Helium

    CERN Document Server

    Shivaram, Niranjan; Timmers, Henry; Sandhu, Arvinder

    2015-01-01

    The evolution of electron wavepackets determines the course of many physical and chemical phenomena and attosecond spectroscopy aims to measure and control such dynamics in real-time. Here, we investigate radial electron wavepacket motion in Helium by using an XUV attosecond pulse train to prepare a coherent superposition of excited states and a delayed femtosecond IR pulse to ionize them. Quantum beat signals observed in the high resolution photoelectron spectrogram allow us to follow the field-free evolution of the bound electron wavepacket and determine the time-dependent ionization dynamics of the low-lying 2p state.

  13. 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 and...... Auger widths, as well as wave functions and dipole coupling matrix elements, are determined by accurate many-body structure calculations. We create a hole in a valence shell by an attosecond pump, couple an inner-shell electron to the hole by an attosecond probe, and then monitor the formation of the...

  14. 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...

  15. 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.

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

    Science.gov (United States)

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

    2016-05-27

    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. PMID:26980312

  17. Attosecond interferometry: techniques and spectroscopy

    OpenAIRE

    Kroon, David

    2016-01-01

    The interaction between an intense laser pulse and a gas medium leads to the emission of coherent bursts of light in the extreme ultraviolet range. This process, known as high-order harmonic generation, has today, almost three decades after its discovery, developed into a reliable source of extremely short (on the order of 100 as) pulses of electromagnetic radiation, with a wide range of applications in the atomic, molecular and optical sciences. The access to radiation with attosecond durati...

  18. X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The methods and results of X-ray photoelectron spectroscopy in the study of plasmons, alloys and gold compounds are discussed. After a comprehensive introduction, seven papers by the author, previously published elsewhere, are reprinted and these cover a wide range of the uses of X-ray photoelectron spectroscopy. (W.D.L.)

  19. Photoelectron photoion molecular beam spectroscopy

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  1. Molecular photoelectron momentum distributions by intense orthogonally polarized attosecond ultraviolet laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2015-10-01

    We study molecular photoelectron momentum distributions (MPMDs) of aligned H2+ by intense orthogonally polarized attosecond ultraviolet laser pulses. Photoionization is simulated by numerically solving corresponding three-dimensional time dependent Schrödinger equations with static nuclei. It is found that altering pulse phases ϕ varies the structure of MPMDs, which is attributed to the interference effect between orthogonal polarization ionizations. The phase ϕ dependent MPMDs are also a function of molecular alignment and pulse wavelengths. Altering the symmetry of initial electronic states offers the possibility of imaging molecular orbitals by orthogonal polarization attosecond MPMDs.

  2. Molecular photoelectron angular distributions with intense attosecond circularly polarized UV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2014-01-01

    We investigate effects of intermediate resonant electronic states on molecular photoelectron angular distributions (MPADs) by intense circularly polarized attosecond UV laser pulses. Simulations are performed on aligned H2+ by numerically solving the corresponding three dimensional time dependent Schrödinger equations. MPADs exhibit signature of rotations, which is shown to be critically sensitive to the symmetry of the intermediate resonant electronic state and the pulse intensity. This sensitivity is attributed to the coherent population transfer in the initial and intermediate resonant states, thus suggesting a method to control molecular photoionization on attosecond time scale.

  3. Combining attosecond XUV pulses with coincidence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sabbar, M., E-mail: msabbar@phys.ethz.ch; Heuser, S.; Boge, R.; Lucchini, M.; Cirelli, C.; Keller, U. [Department of Physics, ETH Zurich, 8093 Zurich (Switzerland); Gallmann, L. [Department of Physics, ETH Zurich, 8093 Zurich (Switzerland); Institute of Applied Physics, University of Bern, 3012 Bern (Switzerland)

    2014-10-15

    Here we present a successful combination of an attosecond beamline with a COLTRIMS apparatus, which we refer to as AttoCOLTRIMS. The setup provides either single attosecond pulses or attosecond pulse trains for extreme ultraviolet-infrared pump-probe experiments. We achieve full attosecond stability by using an active interferometer stabilization. The capability of the setup is demonstrated by means of two measurements, which lie at the heart of the COLTRIMS detector: firstly, we resolve the rotating electric field vector of an elliptically polarized few-cycle infrared laser field by attosecond streaking exploiting the access to the 3D momentum space of the charged particles. Secondly, we show streaking measurements on different atomic species obtained simultaneously in a single measurement making use of the advantage of measuring ions and electrons in coincidence. Both of these studies demonstrate the potential of the AttoCOLTRIMS for attosecond science.

  4. 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)

  5. 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.

  6. Simultaneous observation of forward-backward attosecond photoelectron holography

    CERN Document Server

    Du, Hongchuan; Wang, Huiqiao; Yue, Shengjun; Hu, Bitao

    2015-01-01

    Photoelectron angular momentum distribution of He+ driven by a few-cycle laser is investigated numerically. We simultaneously observe two dominant interference patterns with one shot of lasers by solving the 3D time-dependent Schrodinger equation (TDSE). The analysis of a semiclassical model identi?es these two interference patterns as two kinds of photoelectron holography. The interference pattern with Pz > 0 is a kind of forward rescattering holography, which comes from the interference between direct (reference) and rescattered (signal) forward electrons ionized in the same quarter-cycle. The interference pattern with Pz < 0 is a kind of backward rescattering holography, which comes from the interference between direct electron ionized in the third quarter- cycle and rescattered backward electron ionized in the ?rst quarter-cycle. Moreover, we propose a method to distinguish this backward rescattering holography and intracycle interference patterns of direct electrons. This is an important step for dyna...

  7. Multiphoton transitions for delay-zero calibration in attosecond spectroscopy

    CERN Document Server

    Herrmann, Jens; Chen, Shaohao; Wu, Mengxi; Ludwig, André; Kasmi, Lamia; Schafer, Kenneth J; Gallmann, Lukas; Gaarde, Mette B; Keller, Ursula

    2014-01-01

    The exact delay-zero calibration in an attosecond pump-probe experiment is important for the correct interpretation of experimental data. In attosecond transient absorption spectroscopy the determination of the delay-zero exclusively from the experimental results is not straightforward and may introduce significant errors. Here, we report the observation of quarter-laser-cycle (4{\\omega}) oscillations in a transient absorption experiment in helium using an attosecond pulse train overlapped with a precisely synchronized, moderately strong infrared pulse. We demonstrate how to extract and calibrate the delay-zero with the help of the highly nonlinear 4{\\omega} signal. A comparison with the solution of the time-dependent Schr\\"odinger equation is used to confirm the accuracy and validity of the approach. Moreover, we study the mechanisms behind the quarter-laser-cycle and the better-known half-laser-cycle oscillations as a function of experimental parameters. This investigation yields an indication of the robust...

  8. Coincident photoelectron spectroscopy on superconductors

    International Nuclear Information System (INIS)

    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 Bi2Sr2CaCu2O8 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.

  9. Photoelectron structure factor and diffraction spectroscopy

    International Nuclear Information System (INIS)

    Highlights: • We described all-direction-resolved photoelectron spectroscopy. • Bonding character of energy band is analyzed by photoelectron structure factor. • We succeeded in measuring PED pattern from exfoliated graphene. • New mathematical procedure for diffraction spectroscopy is explained. - Abstract: The information obtained by all-direction-resolved photoelectron spectroscopy for valence band and core levels are described. By measuring two-dimensional photoelectron intensity angular distribution (PIAD) from valence band, the iso-energy cross section of valence band, e.g., the Fermi surface can be observed. In the case of linearly polarized-light excitation, the symmetry relation in the photoelectron excitation process is also displayed as “angular distribution from atomic orbital”, which is used to distinguish the atomic orbitals constituting the energy band. Another important effect in angular distribution is the “photoelectron structure factor (PSF)”, which originates from the interference among photoelectron waves from individual atoms. The bonding character of the energy band can be clarified from the intensity inequivalency between Brillouin zones determined by PSF. On the other hand, the photoelectron from a localized core level is an excellent probe for element-specific atomic structure analysis. Photoelectron diffraction provides information on the surrounding atomic configuration, which is recorded as forward focusing peaks at local interatomic directions and diffraction patterns in PIAD. By combining this diffraction technique with core level spectroscopy – we call it diffraction spectroscopy, one can get access to each atomic site structure and have their electronic property information individually. Direct three-dimensional atomic structure visualization and site specific electronic property analysis methods are reviewed

  10. Rotations of molecular photoelectron angular distributions with intense ultrashort circularly polarized attosecond laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2013-04-01

    Molecular photoelectron angular distributions (MPADs) by intense (I0 ⩾ 1014 W/cm2) circularly polarized ultrashort, few cycle (attosecond) ultraviolet laser pulses are presented from numerical solutions of time dependent Schrödinger equations. For the aligned molecular ion H_2^+, the MPADs exhibit rotations with respect to the polarization and molecular symmetry axes which are determined by the symmetry of the initial electronics states. It is also found that the rotation angle of MPADs is insensitive to the pulse intensity. We attribute these effects to the asymmetry between the parallel and perpendicular (to the molecular axis) polarization photoionization. Influence of the molecular alignment and ionizing pulse ellipticity on the rotation of MPADs is also shown to allow control of the nonsymmetric ionization.

  11. Multiphoton transitions for delay-zero calibration in attosecond spectroscopy

    International Nuclear Information System (INIS)

    The exact delay-zero calibration in an attosecond pump-probe experiment is important for the correct interpretation of experimental data. In attosecond transient absorption spectroscopy the determination of the delay-zero exclusively from the experimental results is not straightforward and may introduce significant errors. Here, we report the observation of quarter-laser-cycle (4ω) oscillations in a transient absorption experiment in helium using an attosecond pulse train overlapped with a precisely synchronized, moderately strong infrared pulse. We demonstrate how to extract and calibrate the delay-zero with the help of the highly nonlinear 4ω signal. A comparison with the solution of the time-dependent Schrödinger equation is used to confirm the accuracy and validity of the approach. Moreover, we study the mechanisms behind the quarter-laser-cycle and the better-known half-laser-cycle oscillations as a function of experimental parameters. This investigation yields an indication of the robustness of our delay-zero calibration approach. (paper)

  12. UV lamp for photoelectron spectroscopy

    International Nuclear Information System (INIS)

    An UV lamp and a differential pumping system which enables to couple the lamp to an ultra-high vacuum chamber (10-9 torr) without using windows, are described. The differential between the pressure inside the discharge chamber and the one in de UHV region, which is of 108-109, is achieved with two pumping states separated by pyrex capillaries having an internal diameter of 0.6 mm. In the first stage, a mechanical pump (10-3 torr) is used; in the second stage, a diffusor pump with a cryogenic trap (N2 liq - 10-7 torr) is employed. The lamp produces, when used with high purity He, narrow lines almost clear at 21.2 eV and 40.8 eV, depending on the discharge chamber pressure, thus eliminating the need of a monochromator. As a high voltage source (3 KV), a commercial unit with a good current control was used, ensuring UV beam stability - an essential characteristic for this lamp if it is employed for photoelectron excitation of crystalline samples. (C.L.B.)

  13. State-of-the-art attosecond metrology

    International Nuclear Information System (INIS)

    Research highlights: → We present a complete setup for investigations with attosecond temporal resoultion. → Few-cycle visible laser pulses are used to generate xray pulses approaching the atomic unit of time. → 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.

  14. 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.

  15. 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…

  16. Photoelectron spectroscopy of heavy atoms and molecules

    International Nuclear Information System (INIS)

    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

  17. 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.

  18. 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.

  19. Anion photoelectron spectroscopy of radicals and clusters

    Energy Technology Data Exchange (ETDEWEB)

    Travis, Taylor R.

    1999-12-16

    Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying {sup 2}{Sigma} and {sup 2}{Pi} states of C{sub 2n}H (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 C{sub 2}H and C{sub 4}H. Other radicals studied include NCN and I{sub 3}. 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 I{sub 3} 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.

  20. 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.

  1. Two-center interference in molecular photoelectron energy spectra with intense attosecond circularly polarized XUV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Bian, Xue-Bin; Bandrauk, André D.

    2014-08-01

    We study two-center electron interference in molecular photoionization processes by intense attosecond circularly polarized extreme ultraviolet (XUV) laser pulses in both symmetric H2+ and nonsymmetric HHe2+ one-electron diatomic systems. Simulations from numerical solutions of time-dependent Schrödinger equations for the oriented symmetric molecular ion H2+ exhibit a signature of interference with double peaks (minima) in molecular attosecond photoelectron energy spectra (MAPES) at critical angles ϑc between the continuum electron momentum pe and the molecular internuclear R axis. The interference patterns are shown to be influenced by the molecular Coulomb potential, leading to a shift of the critical angle ϑc. Dependence of the two-center interference on the pulse ellipticity is also investigated. Furthermore, it is found that the interference phenomena are critically sensitive to the molecular orbital symmetry. For the nonsymmetric molecular ion HHe2+, such double peaks in MAPES also occur, thus suggesting a method for imaging orbitals in molecules by intense ultrashort circularly polarized XUV pulses on the attosecond time scale.

  2. 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...

  3. 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.

  4. 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.

  5. Study of niobium oxidation by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The chemical composition of thin oxide layers, grown on clean niobium, in low oxygen pressure, was studied by a surface analysis method: X-ray Photoelectron Spectroscopy. The purpose of this study was to find the best conditions for the building of Nb/Nb oxide/Pb Josephson junctions, and particularly to minimise the interface thickness during the formation of the insulator film (Nb2O5) on the metal (Nb). This interface is essentially formed by the monoxide (NbO) and dioxide (NbO2). Nb 3d XPS core level peak positions and area ratios (obtained by the signal decomposition) of the components of the total peak, were used to determine the presence of the different oxidation states II, IV and V, their relative abundance, oxide thicknesses and their depth distribution. All this information was extracted by a special numerical procedure

  6. 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.

  7. 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

  8. 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.

  9. Rescattering photoelectron spectroscopy of small molecules

    International Nuclear Information System (INIS)

    Highlights: • We extracted DCSs of electron scattering from ions using electron spectroscopy. • Detail of the extraction procedure of DCS from the experiment is presented. • Experimentally extracted DCSs are compared with ab initio calculations. • Factorization model of rescattering is confirmed for molecules experimentally. - Abstract: We have measured angle-resolved rescattering photoelectron spectra of three small molecules (O2, CO2, and C2H4) using intense near-infrared laser pulses at several laser intensities. Based on the factorization formula for rescattering processes, we have extracted, from the electron spectra, the field-free differential cross sections of elastic electron scattering by the molecular ions. The detail of the extraction procedure is described. The experimentally extracted differential cross sections are compared with theoretical calculations of the field-free differential cross sections. Fairly good agreement between the experimentally extracted and theoretically calculated DCSs for wide range of the collision momentum indicates the validity of the present extraction procedure for the molecules

  10. 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)

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

    International Nuclear Information System (INIS)

    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 MnF2 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

  12. Atomic photoelectron-spectroscopy studies using synchrotron radiation

    International Nuclear Information System (INIS)

    Photoelectron spectroscopy combined with tunable synchrotron radiation has been used to study the photoionization process in several atomic systems. The time structure of the synchrotron radiation source at the Stanford Synchrotron Radiation Laboratory (SSRL) was used to record time-of-flight (TOF) photoelectron spectra of gaseous Cd, Hg, Ne, Ar, Ba, and Mn. The use of two TOF analyzers made possible the measurement of photoelectron angular distributions as well as branching ratios and partial cross sections

  13. Atomic photoelectron-spectroscopy studies using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kobrin, P.H.

    1983-02-01

    Photoelectron spectroscopy combined with tunable synchrotron radiation has been used to study the photoionization process in several atomic systems. The time structure of the synchrotron radiation source at the Stanford Synchrotron Radiation Laboratory (SSRL) was used to record time-of-flight (TOF) photoelectron spectra of gaseous Cd, Hg, Ne, Ar, Ba, and Mn. The use of two TOF analyzers made possible the measurement of photoelectron angular distributions as well as branching ratios and partial cross sections.

  14. Tagging multiphoton ionization events by two-dimensional photoelectron spectroscopy

    OpenAIRE

    de Groot, Mattijs; Broos, Jaap; Buma, Wybren Jan

    2007-01-01

    Two-dimensional photoelectron spectroscopy has been used to supply process-specific labels to multiphoton ionization events. Employing these tags, the authors can construct excitation and photoelectron spectra along predefined excitation routes in the neutral manifold and ionization routes to the ionic manifold from one single two-dimensional photoelectron spectrum. These results offer a novel way to elucidate the vibronic and dynamic properties of excited and ionic states. (c) 2007 American ...

  15. Zero kinetic energy photoelectron spectroscopy of triphenylene

    Energy Technology Data Exchange (ETDEWEB)

    Harthcock, Colin; Zhang, Jie; Kong, Wei, E-mail: wei.kong@oregonstate.edu [Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)

    2014-06-28

    We report vibrational information of both the first electronically excited state and the ground cationic state of jet-cooled triphenylene via the techniques of resonantly enhanced multiphoton ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. The first excited electronic state S{sub 1} of the neutral molecule is of A{sub 1}′ symmetry and is therefore electric dipole forbidden in the D{sub 3h} group. Consequently, there are no observable Franck-Condon allowed totally symmetric a{sub 1}′ vibrational bands in the REMPI spectrum. All observed vibrational transitions are due to Herzberg-Teller vibronic coupling to the E′ third electronically excited state S{sub 3}. The assignment of all vibrational bands as e′ symmetry is based on comparisons with calculations using the time dependent density functional theory and spectroscopic simulations. When an electron is eliminated, the molecular frame undergoes Jahn-Teller distortion, lowering the point group to C{sub 2v} and resulting in two nearly degenerate electronic states of A{sub 2} and B{sub 1} symmetry. Here we follow a crude treatment by assuming that all e′ vibrational modes resolve into b{sub 2} and a{sub 1} modes in the C{sub 2v} molecular frame. Some observed ZEKE transitions are tentatively assigned, and the adiabatic ionization threshold is determined to be 63 365 ± 7 cm{sup −1}. The observed ZEKE spectra contain a consistent pattern, with a cluster of transitions centered near the same vibrational level of the cation as that of the intermediate state, roughly consistent with the propensity rule. However, complete assignment of the detailed vibrational structure due to Jahn-Teller coupling requires much more extensive calculations, which will be performed in the future.

  16. Nonlinear Fourier transformation spectroscopy of small molecules with intense attosecond pulse train

    International Nuclear Information System (INIS)

    We have developed an attosecond nonlinear molecular spectroscopic method called nonlinear Fourier transformation spectroscopy (NFTS) that uses an intense attosecond pulse train (APT) to induce multiphoton ionization processes. In the NFTS method, in addition to characterization of the temporal profile of attosecond pulses, the nonlinear molecular responses are encoded in the interferometric autocorrelation traces depending on the molecular species, their fragment ions and their kinetic energy distributions. The principle and applicability of the NFTS method are described in this paper along with the numerical simulations. The method is applied to diatomic molecules (N2 , D2 and O2) and polyatomic molecules (CO2, CH4 and SF6). Our results highlight the fact that nonlinear spectroscopic information of molecules in the short wavelength region can be obtained through the irradiation of intense APT by taking advantage of the broad spectral bandwidth of attosecond pulses. The development of the nonlinear spectroscopic method in attoseconds is expected to pave the way to investigate the ultrafast intramolecular electron motion such as ultrafast charge migration and electron correlation. (review article)

  17. Nonlinear Fourier transformation spectroscopy of small molecules with intense attosecond pulse train

    Science.gov (United States)

    Okino, T.; Furukawa, Y.; Shimizu, T.; Nabekawa, Y.; Yamanouchi, K.; Midorikawa, K.

    2014-06-01

    We have developed an attosecond nonlinear molecular spectroscopic method called nonlinear Fourier transformation spectroscopy (NFTS) that uses an intense attosecond pulse train (APT) to induce multiphoton ionization processes. In the NFTS method, in addition to characterization of the temporal profile of attosecond pulses, the nonlinear molecular responses are encoded in the interferometric autocorrelation traces depending on the molecular species, their fragment ions and their kinetic energy distributions. The principle and applicability of the NFTS method are described in this paper along with the numerical simulations. The method is applied to diatomic molecules (N2 , D2 and O2) and polyatomic molecules (CO2, CH4 and SF6). Our results highlight the fact that nonlinear spectroscopic information of molecules in the short wavelength region can be obtained through the irradiation of intense APT by taking advantage of the broad spectral bandwidth of attosecond pulses. The development of the nonlinear spectroscopic method in attoseconds is expected to pave the way to investigate the ultrafast intramolecular electron motion such as ultrafast charge migration and electron correlation.

  18. Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

    Science.gov (United States)

    Cheng, Yan; Chini, Michael; Wang, Xiaowei; González-Castrillo, Alberto; Palacios, Alicia; Argenti, Luca; Martín, Fernando; Chang, Zenghu

    2016-08-01

    Attosecond science promises to allow new forms of quantum control in which a broadband isolated attosecond pulse excites a molecular wave packet consisting of a coherent superposition of multiple excited electronic states. This electronic excitation triggers nuclear motion on the molecular manifold of potential energy surfaces and can result in permanent rearrangement of the constituent atoms. Here, we demonstrate attosecond transient absorption spectroscopy (ATAS) as a viable probe of the electronic and nuclear dynamics initiated in excited states of a neutral molecule by a broadband vacuum ultraviolet pulse. Owing to the high spectral and temporal resolution of ATAS, we are able to reconstruct the time evolution of a vibrational wave packet within the excited B'Σ1u+ electronic state of H2 via the laser-perturbed transient absorption spectrum.

  19. Photoelectron spectroscopy as a tool of lignin chemistry

    International Nuclear Information System (INIS)

    Many efforts in systematic elucidation of lignin properties start from the properties of the lignin subunits. In this paper, the authors provide the vertical ionization potentials (IP) of a representative set of lignin model compound. Gas phase photoelectron spectroscopy enables them to determine ionization potentials and makes it possible to deduce the electron structure of molecules within the limitations of Koopman's theorem. They discuss reasons why photoelectron spectroscopy might be a valuable method for the study of lignin properties

  20. Real time tracing of valence-shell electronic coherences with attosecond transient absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wirth, A. [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Santra, R. [Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Department of Physics, University of Hamburg, Jungiusstrasse 9, 20355 Hamburg (Germany); Goulielmakis, E., E-mail: elgo@mpq.mpg.de [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany)

    2013-03-12

    Highlights: ► Detailing the technique of attosecond transient absorption spectroscopy. ► Tracing the charge state time-resolved ionization of atoms. ► Real-time observation and reconstruction of valence electron motion in Kr{sup +} ions. ► Observation of coherences in correlated multi-hole systems: Kr{sup 2+} and xenon ions. - Abstract: The chemical properties of atoms, molecules and of more complex systems such as clusters, nanoparticles or condensed matter systems are determined by valence electrons. Real-time control of these properties requires the capability of tracing as well as of driving valence electrons on their native temporal scale of motion, that is, within tens to thousands of attoseconds. Here we detail the technique of attosecond transient absorption spectroscopy. It combines the extreme sensitivity of core-level spectroscopy with the unprecedented temporal resolution offered by the tools of attosecond technology. We use the technique to demonstrate real-time tracing and complete characterization of coherent electron motion triggered by single, double or multiple ionization of atoms exposed to intense, few-cycle pulses. Our work opens the door to high fidelity, time-domain studies and control of electron dynamics in the microcosm.

  1. Threshold photoelectron spectroscopy of acetaldehyde and acrolein

    International Nuclear Information System (INIS)

    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

  2. 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.

  3. 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.

  4. Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

    International Nuclear Information System (INIS)

    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 → bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN-, NCO- and NCS-. Transition state photoelectron spectra are presented for the following systems Br + HI, Cl + HI, F + HI, F + CH30H,F + C2H5OH,F + OH and F + H2. A time dependent framework for the simulation and interpretation of the bound → free transition state photoelectron spectra is subsequently developed and applied to the hydrogen transfer reactions Br + HI, F + OH → O(3P, 1D) + HF and F + H2. 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 + H2 system, comparisons with three-dimensional quantum calculations are made

  5. Photoelectron spectroscopy of natural products: terpenes

    Science.gov (United States)

    Novak, Igor; Kovač, Branka

    2005-01-01

    HeI photoelectron spectra of three terpenes: α-pinene, pulegone and cembrene have been measured. The analysis of their electronic structure is based on the comparison of measured spectra with those of related compounds and on the comparison with molecular structures of studied compounds. We discuss changes in ionization energies of C-C double bonds which are situated at different positions along the rings.

  6. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H., E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Li, Xiang [Center for Space Science and Technology, University of Maryland–Baltimore County, Baltimore, Maryland 21250 (United States); Kiran, Boggavarapu, E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry and Physics, McNeese State University, Lake Charles, Louisiana 70609 (United States); Kandalam, Anil K. [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, B{sub x}Al{sub y}H{sub z}{sup −}, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  7. Theory of Attosecond Transient Absorption Spectroscopy of Krypton for Overlapping Pump and Probe Pulses

    OpenAIRE

    Pabst, Stefan; Sytcheva, Arina; Moulet, Antoine; Wirth, Adrian; Goulielmakis, Eleftherios; Santra, Robin

    2012-01-01

    We present the first fully ab initio calculations for attosecond transient absorption spectroscopy of atomic krypton with overlapping pump and probe pulses. Within the time-dependent configuration interaction singles (TDCIS) approach, we describe the pump step (strong-field ionization using a near-infrared pulse) as well as the probe step (resonant electron excitation using an extreme- ultraviolet pulse) from first principles. We extent our TDCIS model and account for the spin-orbit splitting...

  8. Valence Electronic Structure of Aqueous Solutions: Insights from Photoelectron Spectroscopy

    Science.gov (United States)

    Seidel, Robert; Winter, Bernd; Bradforth, Stephen E.

    2016-05-01

    The valence orbital electron binding energies of water and of embedded solutes are crucial quantities for understanding chemical reactions taking place in aqueous solution, including oxidation/reduction, transition-metal coordination, and radiation chemistry. Their experimental determination based on liquid-photoelectron spectroscopy using soft X-rays is described, and we provide an overview of valence photoelectron spectroscopy studies reported to date. We discuss principal experimental aspects and several theoretical approaches to compute the measured binding energies of the least tightly bound molecular orbitals. Solutes studied are presented chronologically, from simple electrolytes, via transition-metal ion solutions and several organic and inorganic molecules, to biologically relevant molecules, including aqueous nucleotides and their components. In addition to the lowest vertical ionization energies, the measured valence photoelectron spectra also provide information on adiabatic ionization energies and reorganization energies for the oxidation (ionization) half-reaction. For solutes with low solubility, resonantly enhanced ionization provides a promising alternative pathway.

  9. Pitfalls in measuring work function using photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Accurate measurement of work function is essential in many areas of research and development. Despite the importance of photoelectron spectroscopy as a technique for measuring work function, there has been relatively little discussion in the literature of how to conduct accurate measurements. We review the basic technique of measuring work function using ultraviolet photoelectron spectroscopy and discuss several common sources of error related to the experimental setup. In particular, the sample-detector geometry is found to be a key experimental parameter; accurate results are only obtained when the sample is perpendicular to the electron detector. In addition, we demonstrate that photoelectron work function values correspond to the minimum work function 'patch' on a non-uniform surface, in contrast to the average work function measured by other techniques, such as the Kelvin probe method.

  10. Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Weijie Hua

    2016-03-01

    Full Text Available Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns. We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

  11. X-ray photoelectron spectroscopy: From origins to future directions

    Energy Technology Data Exchange (ETDEWEB)

    Fadleys, Charles S. [Department of Physics, University of California Davis, Davis, CA 95616 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)], E-mail: fadley@physics.ucdavis.edu

    2009-03-21

    In this overview, I will briefly explore some of the earliest seeds of modern X-ray photoelectron spectroscopy, as pioneered by Siegbahn and collaborators, and then turn to some examples of how these seeds have sprouted in several present and promising future applications of this technique. Some of the future areas explored will be the use chemical shifts and multiplet splittings in the study of strongly correlated materials, photoelectron diffraction and holography for atomic structure determinations, standing-wave and hard X-ray excited photoemission for probing buried interfaces and bulk properties, valence-band mapping with soft and hard X-ray excitation, and time-resolved measurements with the sample at high ambient pressures in the multi-torr regime.

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

    International Nuclear Information System (INIS)

    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 ν less than or equal to 360 eV and laboratory sources, is divided into three parts

  13. Photoelectron Angular Distribution and Phase in Two-Photon Single Ionization of H and He by a Femtosecond and Attosecond Extreme-Ultraviolet Pulse

    Directory of Open Access Journals (Sweden)

    Kenichi L. Ishikawa

    2013-03-01

    Full Text Available We theoretically study the photoelectron angular distribution (PAD from the two-photon single ionization of H and He by femtosecond and attosecond extreme-ultraviolet pulses, based on the time-dependent perturbation theory and simulations with the full time-dependent Schrodinger equation. The PAD is formed by the interference of the s and d continuum wave packets, and, thus, contains the information on the relative phase and amplitude ratio between them. We find that, when a spectrally broadened femtosecond pulse is resonant with an excited level, the PAD substantially changes with pulse width, since the competition between resonant and nonresonant ionization paths, leading to distinct from the scattering phase shift difference, changes with it. In contrast, when the Rydberg manifold is excited, and for the case of above-threshold two-photon ionization, and the PAD do not depend much on pulse width, except for the attosecond region. Thus, the Rydberg manifold and the continuum behave similarly in this respect. For a high-harmonic pulse composed of multiple harmonic orders, while the value is different from that for a single-component pulse, the PAD still rapidly varies with pulse width. The present results illustrate a new way to tailor the continuum wave packet.

  14. Photoelectron spectroscopy beamline on Indus-1 synchrotron radiation source

    OpenAIRE

    Chaudhari, SM; Phase, DM; Wadikar, AD; Ramesh, GS; Hegde, MS; Dasannacharya, BA

    2002-01-01

    We describe here a photoelectron spectroscopy beamline installed on Indus-1 storage ring. Initially we give a brief description of optical and mechanical layout of beam-line. The beamline optics was designed to cover energy range from 10 eV to 200 eV and it consists of a pre-focusing mirror, a toroidal grating monochromator and a post-focusing mirror. We then discuss indigenously developed ultra high vacuum compatible work station to carry out angle integrated photoemission experiments. The b...

  15. 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.

  16. Attosecond physics

    International Nuclear Information System (INIS)

    The first part of the thesis is dealing with issues related to the problem of extending time-resolved spectroscopy into attosecond time domain. Despite of first experimental successes, the technique of generating attosecond light pulses is still in its infancy. As a result, important problems and questions remain unanswered. The purpose of this chapter is the temporal and spatial characterization of harmonic attosecond pulses by theoretical means. Here, an ab-initio numerical model is presented, which gives us detailed, quantitative information on the generation and characterization of such pulses. The topic of the second part is the relativistic ionization. Here we introduce the analytic single-electron-response theory of tunnel ionization of hydrogenlike ions in ultrahigh intensity laser fields. Since the problem of relativistic ionization is intrinsically three-dimensional, ionization rates are obtained from a quasi-classical solution of the three-dimensional Klein-Gordon and Dirac equations. This presents the first quantitative determination of tunneling in atomic ions in the relativistic regime. Such a theory opens the possibility to study strong laser field processes with highly charged ions, where relativistic ionization plays a dominant role. An actual example of such a process, where relativistic tunneling plays an essential role, is given in third part of this thesis. Here we make use of two key properties of relativistic ionization: on the one hand, due to the high nonlinearity of the tunneling process, ionized electrons appear in form of free electron pulses with attosecond pulse duration. On the other hand, since the kinetic energy of a laser-accelerated electrons increases with rising intensity, these attosecond electron pulses gain energy in MeV-range in a relativistic laser field. Based on these two facts, we introduce a method to refocus such energetic attosecond electron pulses to the parent nucleus immediately following ionization. Furthermore

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

    Science.gov (United States)

    Kärtner, F. X.; Ahr, F.; Calendron, A.-L.; Çankaya, H.; Carbajo, S.; Chang, G.; Cirmi, G.; Dörner, K.; Dorda, U.; Fallahi, A.; Hartin, A.; Hemmer, M.; Hobbs, R.; Hua, Y.; Huang, W. R.; Letrun, R.; Matlis, N.; Mazalova, V.; Mücke, O. D.; Nanni, E.; Putnam, W.; Ravi, K.; Reichert, F.; Sarrou, I.; Wu, X.; Yahaghi, A.; Ye, H.; Zapata, L.; Zhang, D.; Zhou, C.; Miller, R. J. D.; Berggren, K. K.; Graafsma, H.; Meents, A.; Assmann, R. W.; Chapman, H. N.; Fromme, P.

    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

  18. Rotations of molecular photoelectron angular distributions in above threshold ionization of H2+ by intense circularly polarized attosecond UV laser pulses

    International Nuclear Information System (INIS)

    We present molecular photoelectron angular distributions (MPADs) in multi-photon ionization processes by circularly polarized attosecond UV laser pulses. Simulations are performed on the single electron aligned molecular ion H2+ by solving corresponding 3D time-dependent Schrödinger equations. Numerical results of molecular above threshold ionization (MATI) show that rotations of MPADs with respect to the molecular and polarization axes depend on pulse intensities and photoelectron kinetic energies. We attribute the rotation to Γ, the difference between parallel and perpendicular ionization probabilities. It is found that in a resonant ionization process, the rotation angle is also a function of the symmetry of intermediate electronic states. The coherent population transfer between the initial and the resonant electronic states is controlled by pulse intensities. Such dependence of rotations on the pulse intensity is absent in Rydberg resonant ionizations as well as in MATI at large energy photons ℏω > Ip, where ω is angular frequency of photons and Ip is the molecular ionization potential. We describe these processes by a multi-photon perturbation theory model. Effects of molecular alignment and pulse ellipticities on rotations are investigated, confirming the essence of the ionization parameter Γ in rotations of MPADs. (paper)

  19. Rotations of molecular photoelectron angular distributions in above threshold ionization of H2+ by intense circularly polarized attosecond UV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2014-10-01

    We present molecular photoelectron angular distributions (MPADs) in multi-photon ionization processes by circularly polarized attosecond UV laser pulses. Simulations are performed on the single electron aligned molecular ion H_2^+ by solving corresponding 3D time-dependent Schrödinger equations. Numerical results of molecular above threshold ionization (MATI) show that rotations of MPADs with respect to the molecular and polarization axes depend on pulse intensities and photoelectron kinetic energies. We attribute the rotation to Γ, the difference between parallel and perpendicular ionization probabilities. It is found that in a resonant ionization process, the rotation angle is also a function of the symmetry of intermediate electronic states. The coherent population transfer between the initial and the resonant electronic states is controlled by pulse intensities. Such dependence of rotations on the pulse intensity is absent in Rydberg resonant ionizations as well as in MATI at large energy photons ℏω > Ip, where ω is angular frequency of photons and Ip is the molecular ionization potential. We describe these processes by a multi-photon perturbation theory model. Effects of molecular alignment and pulse ellipticities on rotations are investigated, confirming the essence of the ionization parameter Γ in rotations of MPADs.

  20. Ultrafast photoelectron spectroscopy of solutions: space-charge effect

    Science.gov (United States)

    Al-Obaidi, R.; Wilke, M.; Borgwardt, M.; Metje, J.; Moguilevski, A.; Engel, N.; Tolksdorf, D.; Raheem, A.; Kampen, T.; Mähl, S.; Kiyan, I. Yu; Aziz, E. F.

    2015-09-01

    The method of time-resolved XUV photoelectron spectroscopy is applied in a pump-probe experiment on a liquid micro-jet. We investigate how the XUV energy spectra of photoelectrons are influenced by the space charge created due to ionization of the liquid medium by the pump laser pulse. XUV light from high-order harmonic generation is used to probe the electron population of the valence shell of iron hexacyanide in water. By exposing the sample to a short UV pump pulse of 266 nm wavelength and ˜55 fs duration, we observe an energy shift of the spectral component associated with XUV ionization from the Fe 3d(t2g) orbital as well as a shift of the water spectrum. Depending on the sequence of the pump and probe pulses, the arising energy shift of photoelectrons acquires a positive or negative value. It exhibits a sharp positive peak at small time delays, which facilitates to determine the temporal overlap between pump and probe pulses. The negative spectral shift is due to positive charge accumulated in the liquid medium during ionization. Its dissipation is found to occur on a (sub)nanosecond time scale and has a biexponential character. A simple mean-field model is provided to interpret the observations. A comparison between the intensity dependencies of the spectral shift and the UV ionization yield shows that the space-charge effect can be significantly reduced when the pump intensity is attenuated below the saturation level of water ionization. For the given experimental conditions, the saturation intensity lies at 6× {10}10 W cm-2.

  1. Attosecond Strong-Field Interferometry of Electron Dynamics

    International Nuclear Information System (INIS)

    Interference effects arising during the highly nonlinear interaction of intense laser pulses with matter are presented for applications in attosecond spectroscopy and interferometry. In the first part we theoretically describe an approach to excite and measure bound electron wavepackets where temporal interference in the photoelectron momentum spectrum reveals the complete energy-level structure of an atom. In the second part we analyse and discuss experimentally observed interference patterns of few adjacent attosecond pulses generated in neon gas that can be controlled by varying experimental parameters such as carrier-envelope phase (CEP) or pressure.

  2. Exploring covalently bonded diamondoid particles with valence photoelectron spectroscopy

    CERN Document Server

    Zimmermann, Tobias; Knecht, Andre; Fokin, Andrey A; Koso, Tetyana V; Chernish, Lesya V; Gunchenko, Pavel A; Schreiner, Peter R; Möller, Thomas; Rander, Torbjörn

    2013-01-01

    We investigated the electronic structures of diamondoid particles in the gas phase, utilizing valence photoelectron spectroscopy. The samples were singly or doubly covalently bonded dimers or trimers of the lower diamondoids. Both bond type and the combination of the bonding partners affect the overall electronic structures. For singly bonded particles we observe a small impact of the bond type on the electronic structure, whereas for doubly bonded particles the connecting bond is the deciding factor, determining the electronic structure of the uppermost occupied orbitals. In the singly bonded particles a superposition of the bonding partner orbitals determines the overall electronic structure. The strength of quantum confinement effects, i.e., the localization of electrons, depends on the bonding partner orbital energy difference. The experimental findings correspond well to density functional theory computations.

  3. 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.

  4. An instrument for the investigation of actinides with spin resolved photoelectron spectroscopy and bremsstrahlung isochromat spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yu, S.-W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tobin, J. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chung, B. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2011-01-01

    A new system for spin resolved photoelectron spectroscopy and bremsstrahlung isochromat spectroscopy has been built and commissioned at Lawrence Livermore National Laboratory for the investigation of the electronic structure of the actinides.Actinide materials are very toxic and radioactive and therefore cannot be brought to most general user facilities for spectroscopic studies. The technical details of the new system and preliminary data obtained therein will be presented and discussed.

  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. Carbon-13 spin lattice relaxation and photoelectron spectroscopy of some aromatic sulphides and sulphones

    International Nuclear Information System (INIS)

    Carbon-13 NMR spectroscopy and photoelectron spectroscopy have been used to study the electronic structure of symmetric dithienothiophenes and corresponding sulphones. The physical data obtained from both spectroscopic techniques have been interpreted with the aid of quantum mechanical calculations. (Auth.)

  7. 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...

  8. Zero Kinetic Energy Photoelectron Spectroscopy of Benzo[h]quinoline.

    Science.gov (United States)

    Harthcock, Colin; Zhang, Jie; Kong, Wei

    2015-12-17

    We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[h]quinoline (BhQ) via resonantly enhanced multiphoton ionization (REMPI) through the first electronically excited state S1. From the simulated REMPI spectra with and without Herzberg-Teller coupling, we conclude that vibronic coupling plays a minor but observable role in the electronic excitation to the S1 state. We further compare the S1 state of BhQ with the first two electronically excited states of phenanthrene, noticing a similarity of the S1 state of BhQ with the second electronically excited state S2 of phenanthrene. In the ZEKE spectra of BhQ, the vibrational frequencies of the cationic state D0 are consistently higher than those of the intermediate neutral state, indicating enhanced bonding upon ionization. The sparse ZEKE spectra, compared with the spectrum of phenanthrene containing rich vibronic activities, further imply that the nitrogen atom has attenuated the structural change between S1 and D0 states. We speculate that the nitrogen atom can withdraw an electron in the S1 state and donate an electron in the D0 state, thereby minimizing the structural change during ionization. The origin of the first electronically excited state is determined to be 29,410 ± 5 cm(-1), and the adiabatic ionization potential is determined to be 65,064 ± 7 cm(-1). PMID:26039927

  9. Photoelectron spectroscopy investigation of the C60/calcium interface

    Energy Technology Data Exchange (ETDEWEB)

    Wetzstein, Holger; Schoell, Achim; Reinert, Friedrich [Experimental Physics VII, Julius-Maximilians-University of Wuerzburg, D-97074 Wuerzburg (Germany); Bunandar, Darius [Department of Physics, University of Texas at Austin, Austin, TX 78712-0264 (United States); Schafferhans, Julia; Deibel, Carsten [Experimental Physics VI, Julius-Maximilians-University of Wuerzburg, D-97074 Wuerzburg (Germany)

    2011-07-01

    Device lifetime is a crucial point for organic solar cells. Therefore it is important to understand the degradation mechanisms as well as their consequence on the performance of these photovoltaic devices. We observed a characteristic S-shape in the I/V-curves of P3HT/PCBM-bulk heterojunction cells with calcium contacts. A tentative origin of this behavior is a reaction of the calcium with oxygen, which leads to alterations in the regime of the anode interface. To shed more light on this issue we investigated the electronic structure of the Ca/C{sub 60} interface, which serves as a model for the PCBM/Ca contact. X-ray (XPS) and ultra-violet photoelectron spectroscopy (UPS) measurements were performed on C{sub 60} layers adsorbed on epitaxially grown Calcium as well as on Ca deposited on C{sub 60}. In both cases, the data clearly show the formation of an interface state due to the charge transfer from the Ca into the C{sub 60}, which is an indication for a chemical reaction. Moreover, we studied the effect of oxygen exposure on the interfacial chemical and electronic structure under conditions comparable to the conditions during device operation.

  10. Valence bands offset between depleted semiconductors measured by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    A modified method to measure the valence bands offset by photoelectron spectroscopy (PES) between low doped and depleted semiconductors have been used. The surface photovoltage (SPV) and the charging effects modify the PES spectra of depleted semiconductors. The valence bands offset at the heterojunction of depleted ZnSe film and doped GaAs substrate have been measured. These samples were prepared by the laser ablation technique. The shift of PES spectra of ZnSe by about 6 eV has been observed due to the charging and SPV effects. The charging and SPV effects on PES spectra, have been reduced to negligible values in the presence of excess plasma (due to absorption from a secondary white light source) density of the order of 1018 cm-3. The effect of the charging and SPV is very small on the value of the valence bands offset measured in the presence of the excess plasma. This method to measure the valence bands offset is useful for samples prepared in ex situ conditions and with film thickness of the order of 100 nm

  11. 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.

  12. Ultraviolet photoelectron spectroscopy of supported mass selected silver clusters

    Energy Technology Data Exchange (ETDEWEB)

    Wortmann, Ben; Mende, Kolja; Duffe, Stefanie; Groenhagen, Niklas; Hoevel, Heinz [Experimentelle Physik I, Technische Universitaet Dortmund (Germany); Issendorff, Bernd von [Fakultaet fuer Physik, Universitaet Freiburg (Germany)

    2010-05-15

    Ultraviolet photoelectron spectroscopy (UPS) was used to investigate size selected Ag{sub 923{+-}}{sub 9} and Ag{sub 55} clusters which were softlanded on a clean graphite substrate (HOPG) at 100 and 50 K, respectively. With increasing cluster coverage closer to the centre of the deposition spot a continuous change of the d-band signal is observed. Differences in the fine structure of the d-band and comparison to UPS spectra of clusters grown at nanopits on HOPG show that the clusters in the centre of the deposition spot coalesced. However, Ag{sub 55} spectra measured at the rim of the deposition spot indicate that the clusters stay separated in regions of lower coverage for a deposition temperature of 50 K. This is corroborated by scanning tunnelling microscopy (STM) images measured at 5 K using 1 monolayer (ML) Xe to fix the Ag{sub 55} clusters to the substrate, thus making them observable with STM. By comparison to UPS data taken on different sample positions in a 1 x 1 mm{sup 2} grid it was determined that at the rim of the deposition spot the coverage of 30 clusters per 100 x 100 nm{sup 2} was low enough for an UPS measurement of single separated Ag{sub 55} clusters. Differences in the spectra for the largest coverage of Ag{sub 55} and Ag{sub 923} clusters in the deposition spot centre indicate that the resulting Ag film has a partial (111) orientation for the deposition of Ag{sub 55} at 50 K whereas it is mostly polycrystalline for Ag{sub 923} deposited at 100 K. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  13. 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....

  14. Size Effects in Angle-Resolved Photoelectron Spectroscopy of Free Rare-Gas Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Rolles, D.; Zhang, H.; Pesic, Z.D.; Bilodeau, R.C.; Wills, A.; Kukk, E.; Rude, B.S.; Ackerman, G.D.; Bozek, J.D.; Muino, R.D.; de Abajo, F.J.G.; Berrah, N.; /Western

    2007-05-23

    The photoionization of free Xe clusters is investigated by angle-resolved time-of-flight photoelectron spectroscopy. The measurements probe the evolution of the photoelectron angular distribution parameter as a function of photon energy and cluster size. While the overall photon-energy-dependent behavior of the photoelectrons from the clusters is very similar to that of the free atoms, distinct differences in the angular distribution point at cluster-size-dependent effects. Multiple scattering calculations trace their origin to elastic photoelectron scattering.

  15. 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

  16. Obtaining two attosecond pulses pulses for x-ray stimulated Raman spectroscopy

    International Nuclear Information System (INIS)

    Attosecond x-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft x-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each x-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 attoseconds. The carrier frequency of each x-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 attoseconds precision.

  17. High resolution photoelectron spectroscopy of clusters of Group V elements

    International Nuclear Information System (INIS)

    High resolution HeI (580 angstrom) photoelectron spectra of As2, As4, and P4 were obtained with a newly-built high temperature molecular beam source. Vibrational structure was resolved in the photoelectron spectra of the three cluster species. The Jahn-Teller effect is discussed for the 2E and 2T2 states of P4+ and As4+. As a result of the Jahn-Teller effect, the 2E state splits into two bands, and the 2T2 state splits into three bands, in combination with the spin-orbit effect. It was observed that the ν2 normal vibrational mode was involved in the vibronic interaction of the 2E state, while both the ν2 and ν3 modes were active in the 2T2 state. 26 refs., 5 figs., 3 tabs

  18. High-order multiphoton ionization photoelectron spectroscopy of NO

    International Nuclear Information System (INIS)

    Photoelectron energy and angular distributions of NO following three different high-order multiphoton ionization (MPI) schemes have been measured. The 3+3 resonantly enhanced multiphoton ionization (REMPI) via the A2Σ+ (v=0) level yielded a distribution of electron energies corresponding to all accessible vibrational levels (v+=0--6) of the nascent ion. Angular distributions of electrons corresponding to v+=0 and v+=3 were significantly different. The 3+2 REMPI via the A2Σ+ (v=1) level produced only one low-energy electron peak (v+=1). Nonresonant MPI at 532 nm yielded a distribution of electron energies corresponding to both four- and five-photon ionization. Prominent peaks in the five-photon photoelectron spectrum (PES) suggest contributions from near-resonant states at the three-photon level

  19. Plasmon excitation in valence shell photoelectron spectroscopy for PAHs

    International Nuclear Information System (INIS)

    The photon energy dependence of photoelectron spectra (PES) for two members of the polycyclic aromatic hydrocarbon (PAH) family namely pyrene and fluorene is studied in FUV regime (15 - 40 eV) using high-resolution synchrotron photoelectron spectrometer. The difference in outer (π dominated) and inner (σ dominated) valence relative photoelectron emission cross sections as a function of photon energy identifies the region of plasmon excitation (∼ 15-27 eV). This excitation mode is present in the same region for both the molecule irrespective of the difference in their structure and symmetry. The feature is observed to be independent of the details of the molecular orbital associated with the outgoing electron. The results are in contradiction to the observed in benzene for inner valence bands. With the help of OVGF/cc-pVDZ calculations, the experimental bands are assigned as per their binding energy and symmetry. The first ionization potentials are estimated to be 7.436 ± 0.015 and 7.944 ± 0.055 eV for pyrene and fluorene, respectively

  20. Imaging photoelectron photoion coincidence spectroscopy with velocity focusing electron optics

    International Nuclear Information System (INIS)

    An imaging photoelectron photoion coincidence spectrometer at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source is presented and a few initial measurements are reported. Monochromatic synchrotron VUV radiation ionizes the cooled or thermal gas-phase sample. Photoelectrons are velocity focused, with better than 1 meV resolution for threshold electrons, and also act as start signal for the ion time-of-flight analysis. The ions are accelerated in a relatively low, 40-80 V cm-1 field, which enables the direct measurement of rate constants in the 103-107 s-1 range. All electron and ion events are recorded in a triggerless multiple-start/multiple-stop setup, which makes it possible to carry out coincidence experiments at >100 kHz event frequencies. As examples, the threshold photoelectron spectrum of the argon dimer and the breakdown diagrams for hydrogen atom loss in room temperature methane and the chlorine atom loss in cold chlorobenzene are shown and discussed.

  1. Atomic and molecular photoelectron and Auger-electron-spectroscopy studies using synchrotron radiation

    International Nuclear Information System (INIS)

    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 also 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 of the ejected electrons. The double-angle-TOF method for the measurement of photoelectron angular distributions is discussed. This technique offers the advantages of increased electron collection efficiency and the elimination of certain systematic errors. An electron spectroscopy study of inner-shell photoexcitation and ionization of Xe, photoelectron angular distributions from H2 and D2, and photoionization cross sections and photoelectron asymmetries of the valence orbitals of NO are reported

  2. Beam-line systems for pump-probe photoelectron spectroscopy using SR and laser

    CERN Document Server

    Kamada, M; Takahashi, K; Doi, Y I; Fukui, K; Kinoshita, T; Haruyama, Y; Asaka, S; Fujii, Y; Itoh, M

    2001-01-01

    Combined systems for photoelectron spectroscopy using synchrotron radiation (SR) and laser have been constructed at BL5A and BL6A2 in the UVSOR facility, Okazaki. The systems consist of photoelectron spectrometers with high performance, mode-locked lasers, and timing electronic circuits. The laser pulses with repetition frequency of 90 MHz are synchronized with the SR pulses. An upgrade project to install a micro-ESCA at BL6A2, which is now in progress, is also reported.

  3. Development of the web-based NIST X-ray Photoelectron Spectroscopy (XPS) Database

    OpenAIRE

    Angela Y. Lee; Blakeslee, Dorothy M; Powell, Cedric J; Rumble, Jr., John

    2006-01-01

    The first Web-based version of the NIST X-ray Photoelectron Spectroscopy Database (XPSDB) is described. The current database, built from a relational database management system (RDBMS), contains critically evaluated data with over 19,000 line positions, chemical shifts, doublet splittings, and energy separations of photoelectron and Auger-electron lines. It is available free of charge to the public through the Internet at http://srdata.nist.gov/xps/.

  4. Scandium oxide coated polycrystalline tungsten studied using emission microscopy and photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Thermionic electron emission from 200 to 500 nm thick coatings of scandium oxide on tungsten foil have been examined in thermionic emission microscopy, spectroscopic photoelectron microcopy, synchrotron radiation and ultraviolet photoelectron spectroscopy (UPS). A clear dependence of the scandium oxide-W electron yield on the grain orientation of the polycrystalline tungsten is observed in thermionic emission and photoelectron emission. -- Highlights: ► Polycrystalline tungsten imaged with spectroscopic thermionic emission microcopy. ► Scandium oxide coated tungsten grains observed during thermionic emission. ► Direct visualization of the surface electron yield due to oxide coatings. ► Findings related to thermionic cathodes.

  5. Isolated attosecond pulses from ionization gating of high-harmonic emission

    Energy Technology Data Exchange (ETDEWEB)

    Abel, Mark J., E-mail: abelm@berkeley.edu [Departments of Chemistry and Physics, University of California, Berkeley, CA 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Pfeifer, Thomas; Nagel, Phillip M.; Boutu, Willem; Bell, M. Justine; Steiner, Colby P.; Neumark, Daniel M. [Departments of Chemistry and Physics, University of California, Berkeley, CA 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Leone, Stephen R., E-mail: srl@berkeley.edu [Departments of Chemistry and Physics, University of California, Berkeley, CA 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2009-12-10

    Combining results from several techniques of attosecond spectroscopy, we show that ionization gating of high-harmonic emission on the leading edge of the driving pulse produces isolated attosecond pulses with a contrast ratio (the energy in the main pulse normalized to the energy in adjacent satellite pulses) c=3.3{+-}0.2. Half-cycle cutoff analysis confirms that harmonic generation proceeds in the ionization-gated regime. The attosecond pulse contrast is measured using the technique of carrier-envelope phase (CEP)-scanning, recently developed by our group, in which photoelectrons generated from Ne atoms by the harmonic pulse are streaked as a function of CEP. Streaking of photoelectrons as a function of attosecond time delay also confirms the isolated nature of the harmonic pulse, which is measured to have a duration of 430{+-}15 as, limited by the bandwidth of the reflective X-ray optics employed. The combined measurements imply that the experimental advantages of the ionization gating technique-tunable X-ray emission, relaxed sensitivity to the CEP and scalability to longer driver pulses-are also conferred on isolated attosecond pulse production.

  6. Decoherence in Attosecond Photoionization

    OpenAIRE

    Pabst, Stefan; Greenman, L.; Ho, P; Mazziotti, D.; Santra, Robin

    2011-01-01

    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, it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion...

  7. Anion Photoelectron Spectroscopy of NbW- and W2-

    Science.gov (United States)

    Schnepper, D. Alex; Baudhuin, Melissa A.; Leopold, Doreen; Casey, Sean M.

    2015-06-01

    The 488 nm vibrationally-resolved photoelectron spectra of NbW- and W2- are reported. The electron affinity of W2 ( 1σg+ ← 2σu+ ) is found to be 1.118 ± 0.007 eV, which differs from the value reported in a previous anion photoelectron spectroscopic study of W2- (1.46 eV), but was accurately predicted by density functional calculations (1.12 eV). The fundamental vibrational frequency of W2 is measured to be 345 ± 15 wn, in agreement with the value previously reported in matrix resonance Raman studies (337 wn). The W2- anion is measured to have a fundamental frequency of 320 ± 15 wn. Several weak transitions to excited electronic states are seen and tentatively assigned based on calculated energies. NbW has an electron affinity of 0.856 ± 0.007 eV. Vibrational frequencies are found, by Franck-Condon fitting of overlapping transitions, to be 365 ± 20 cm-1 for NbW- and 410 ± 20 cm-1 for NbW. This increase in vibrational frequency upon photodetachment suggests that the extra electron is in an antibonding orbital, leading to ground state assignments of 3Δ and 2Δ for the anion and neutral, respectively. These results are compared to those obtained for other Group V and Group VI transition metal dimers and trends are discussed. H. Weidele et al., Chem. Phys. Lett. 237 (1995) 425-431 Z. J. Wu, X. F. Ma, Chem. Phys. Lett. 371 (2003) 35-39 Z. Hu, J.-G. Dong, J. R. Lombardi, D. M. Lindsay, J. Chem. Phys. 97 (1992) 8811-8812

  8. Interlayer composition in Mo-Si multilayers using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Molybdenum-silicon multilayers have been synthesized using electron beam evaporation method. The chemical nature of surfaces and interfaces are probed using a depth profile X-ray photoelectron spectroscopy. X-ray photoelectron spectroscopy results indicate the formation of MoSi2 phase on both the interfaces. The experimental results agree well with predicted results based on solid-state amorphizing reaction, as a result of large heat of mixing. The effective heat of formation model reveals the formation of MoSi2 as the first phase

  9. Obtaining two attosecond pulses for X-ray stimulated Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Penn, G., E-mail: gepenn@lbl.go [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2010-01-01

    Attosecond X-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft X-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each X-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 as. The carrier frequency of each X-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 as precision.

  10. Obtaining two attosecond pulses for X-ray stimulated Raman spectroscopy

    International Nuclear Information System (INIS)

    Attosecond X-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft X-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each X-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 as. The carrier frequency of each X-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 as precision.

  11. Imaging electron dynamics with time- and angle-resolved photoelectron spectroscopy

    CERN Document Server

    Popova-Gorelova, Daria; Santra, Robin

    2016-01-01

    We theoretically study how time- and angle-resolved photoemission spectroscopy can be applied for imaging coherent electron dynamics in molecules. We consider a process in which a pump pulse triggers coherent electronic dynamics in a molecule by creating a valence electron hole. An ultrashort extreme ultraviolet (XUV) probe pulse creates a second electron hole in the molecule. Information about the electron dynamics is accessed by analyzing angular distributions of photoemission probabilities at a fixed photoelectron energy. We demonstrate that a rigorous theoretical analysis, which takes into account the indistinguishability of transitions induced by the ultrashort, broadband probe pulse and electron hole correlation effects, is necessary for the interpretation of time- and angle-resolved photoelectron spectra. We show how a Fourier analysis of time- and angle-resolved photoelectron spectra from a molecule can be applied to follow its electron dynamics by considering photoelectron distributions from an indol...

  12. Structural and electronic characterization of self-assembled molecular nanoarchitectures by X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Gulino, Antonino

    2013-02-01

    Molecular monolayers and similar nanoarchitectures are indicative of the promising future of nanotechnology. Therefore, many scientists recently devoted their efforts to the synthesis, characterization, and properties of mono- and multilayer-based systems. In this context, X-ray photoelectron spectroscopy is an important technique for the in-depth chemical and structural characterization of nanoscopic systems. In fact, it is a surface technique suitable for probing thicknesses of the same order of the photoelectron inelastic mean free paths (a few tens of ångströms) and allows one to immediately obtain qualitative and quantitative data, film thickness, surface coverage, molecule footprint, oxidation states, and presence of functional groups. Nevertheless, other techniques are important in obtaining a complete spectroscopic characterization of the investigated systems. Therefore, in the present review we report on X-ray photoelectron spectroscopy of self-assembled molecular mono- and multilayer materials including some examples on which other characterization techniques produced important results. PMID:23014858

  13. Hydrogen bonds in the nucleobase-gold complexes: Photoelectron spectroscopy and density functional calculations

    Science.gov (United States)

    Cao, Guo-Jin; Xu, Hong-Guang; Li, Ren-Zhong; Zheng, Weijun

    2012-01-01

    The nucleobase-gold complexes were studied with anion photoelectron spectroscopy and density functional calculations. The vertical detachment energies of uracil-Au-, thymine-Au-, cytosine-Au-, adenine-Au-, and guanine-Au- were estimated to be 3.37 ± 0.08 eV, 3.40 ± 0.08 eV, 3.23 ± 0.08 eV, 3.28 ± 0.08 eV, and 3.43 ± 0.08 eV, respectively, based on their photoelectron spectra. The combination of photoelectron spectroscopy experiments and density functional calculations reveals the presence of two or more isomers for these nucleobase-gold complexes. The major isomers detected in the experiments probably are formed by Au anion with the canonical tautomers of the nucleobases. The gold anion essentially interacts with the nucleobases through N-H...Au hydrogen bonds.

  14. 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.

  15. 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

  16. Angle Resolved X-ray Photoelectron Spectroscopy Study of Pd/NbOx/Nb Interfaces

    Czech Academy of Sciences Publication Activity Database

    Thiam, Michel Malick; Bastl, Zdeněk

    507-510, - (2002), s. 678-682. ISSN 0039-6028 R&D Projects: GA ČR GA202/99/1714; GA ČR GV202/98/K002 Institutional research plan: CEZ:AV0Z4040901 Keywords : photoelectron spectroscopy * palladium * metallic films Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.140, year: 2002

  17. X-ray Photoelectron Spectroscopy Investigation on Electrochemical Degradation of Proton Exchange Membrane Fuel Cell Electrodes

    DEFF Research Database (Denmark)

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

    2015-01-01

    X-ray photoelectron spectroscopy studies were systematically carried out on the electrodes before and after the electrochemical stress tests in an aqueous electrolyte at 20 °C and 70 °C. The electrodes have different ionomer structures (no ionomer, only ionomer, physically mixed ionomer and hot...

  18. X-ray Photoelectron Spectroscopy (XPS), Rutherford Back Scattering (RBS) studies

    Science.gov (United States)

    Neely, W. C.; Bozak, M. J.; Williams, J. R.

    1993-01-01

    X-ray photoelectron spectroscopy (XPS), Rutherford Back Scattering (RBS) studies of each of sample received were completed. Since low angle X-ray could not be performed because of instrumentation problems, Auger spectrometry was employed instead. The results of these measurements for each of the samples is discussed in turn.

  19. 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 of the...

  20. Accessing molecule-metal and hetero-molecular interfaces with direct and resonant photoelectron spectroscopy

    OpenAIRE

    Sauer, Christoph

    2015-01-01

    This thesis consists of two parts of original experimental work, its evaluation, and in- terpretation. Its final goal is to investigate dynamical charge transfer (CT) at a hetero- molecular interface with resonant photoelectron spectroscopy (RPES). In order to achieve this goal preliminary studies have been necessary. First two hetero-molecular inter- faces that exhibit adequate structural properties as well as an appropriate photoelec- tron spectroscopy (PES) spectrum of the valence regime h...

  1. X-ray photoelectron spectroscopy peak assignment for perfluoropolyether oils

    Science.gov (United States)

    Mori, Shigeyuki; Morales, Wilfredo

    1990-01-01

    Perfluoroalkylpolyether (PFPE) oils are increasingly being used as vacuum pump oils and as lubricants for magnetic recording media and instrumentation for satellites. In this paper, the relative binding energies of three PFPE oils are determined. When sample oils are continuously irradiated during X-ray spectroscopy (XPS) measurements, the relative peak intensity of the spectra is altered significantly, indicating that gaseous products form from the oils during XPS measurements. Thus, attention should be paid to chemical changes when XPE is used to characterize fluorinated carbons such as PFPE oils.

  2. The Utilization of Spin Polarized Photoelectron Spectroscopy as a Probe of Electron Correlation with an Ultimate Goal of Pu

    International Nuclear Information System (INIS)

    We are developing the technique of spin-polarized photoelectron spectroscopy as a probe of electron correlation with the ultimate goal of resolving the Pu electronic structure controversy. Over the last several years, we have demonstrated the utility of spin polarized photoelectron spectroscopy for determining the fine details of the electronic structure in complex systems such as those shown in the paper.

  3. Surface sensitivity of Auger-electron spectroscopy and X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    A convenient measure of surface sensitivity in Auger-electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) is the mean escape depth (MED). If the effects of elastic-electron scattering are neglected, the MED is equal to the electron inelastic mean free path (IMFP) multiplied by the cosine of the emission angle with respect to the surface normal, and depends on the material and electron energy of interest. An overview is given here of recent calculations of IMFPs for 50-2000 eV electrons in a range of materials. This work has led to the development of a predictive formula based on the Bethe equation for inelastic electron scattering in matter from which IMFPs can be determined. Estimates show, however, that elastic-electron scattering can significantly modify the MED. Thus, for AES, the MED will be reduced by up to about 35%. For XPS, however, the MED can be changed by up to ±30% for common measurement conditions although it can be much larger (by up to a factor of 2) for near-grazing emission angles. Ratios of MED values, calculated with elastic scattering considered and neglected for XPS from the 3s, 3p, and 3d subshells of silver with Mg Kα X-rays are approximately constant (to about 10%) over a range of emission angles that varies from 40 to 60 depending on the subshell and the angle of X-ray incidence. Recommendations are given on how to determine the optimum range of emission angles for satisfactory analysis of angle-resolved XPS (ARXPS) data. Definitions are included of three terms often used for describing surface sensitivity (IMFP, MED, and effective attenuation length (EAL)), and examples are given of the varying magnitudes of these quantities for different analytical conditions. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  4. Soft landing deposition of mass-selected Ag+-ions and their investigation by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Silver ions are formed by a sputtering cluster ion source and deposited on HOPG substrates. The samples are investigated in situ by photoelectron spectroscopy using an helium lamp and an elliptical electron energy analyzer. Photoelectron spectra are taken for different substrate temperatures, deposition energies, and coverages of the substrate. We find that in order to reach a high sticking coefficient of the ions on the surface, it is necessary to lower their kinetic energy to below 10 eV. The spectra indicate that at a sample temperature of 78 K the Ag atoms are immobile, and that we are able to investigate individual atoms on HOPG. (author)

  5. Probing the Dynamics of Rydberg and Valence States of Molecular Nitrogen with Attosecond Transient Absorption Spectroscopy.

    Science.gov (United States)

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

    2016-05-19

    An attosecond pulse is used to create a wavepacket in molecular nitrogen composed of multiple bound and autoionizing electronic states of Rydberg and valence character between 12 and 16.7 eV. A time-delayed, few-femtosecond, near-infrared (NIR) laser pulse is used to couple individual states in the wavepacket to multiple neighboring states, resulting in time-dependent modification of the absorption spectrum and revealing both individual quantum beats of the wavepacket and the energy shifts of the excited states in the presence of the strong NIR field. The broad bandwidth of the attosecond pulse and high energy resolution of the extreme ultraviolet spectrometer allow the simultaneous observation of time-dependent dynamics for many individual vibrational levels in each electronic state. Quantum beating with periods from 1.3 to 12 fs and transient line shape changes are observed among vibrational levels of a progression of electronically autoionizing Rydberg states leading to the excited A (2)Πu N2(+) ion core. Vibrational levels in the valence b (1)Πu state exhibit 50 fs oscillation periods, revealing superpositions between individual vibrational levels within this state. Comparisons are made to previous studies of electronic wavepackets in atoms that highlight similarities to atomic behavior yet illustrate unique contributions of the diatomic molecular structure to the wavepacket, including the influence of different electronic potentials and vibrational-level-specific electronic dynamics. PMID:26862883

  6. 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.

  7. Observation of Strong Resonant Behavior in the Inverse Photoelectron Spectroscopy of Ce Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J G; Yu, S W; Chung, B W; Waddill, G D; Damian, E; Duda, L; Nordgren, J

    2009-12-15

    X-ray Emission Spectroscopy (XES) and Resonant Inverse Photoelectron Spectroscopy (RIPES) have been used to investigate the photon emission associated with the Ce3d5/2 and Ce3d3/2 thresholds. Strong resonant behavior has been observed in the RIPES of Ce Oxide near the 5/2 and 3/2 edges. Inverse Photoelectron Spectroscopy (IPES) and its high energy variant, Bremstrahlung Isochromat Spectroscopy (BIS), are powerful techniques that permit a direct interrogation of the low-lying unoccupied electronic structure of a variety of materials. Despite being handicapped by counting rates that are approximately four orders of magnitude less that the corresponding electron spectroscopies (Photoelectron Spectroscopy, PES, and X-ray Photoelectron Spectroscopy, XPS) both IPES and BIS have a long history of important contributions. Over time, an additional variant of this technique has appeared, where the kinetic energy (KE) of the incoming electron and photon energy (hv) of the emitted electron are roughly the same magnitude as the binding energy of a core level of the material in question. Under these circumstances and in analogy to Resonant Photoelectron Spectroscopy, a cross section resonance can occur, giving rise to Resonant Inverse Photoelectron Spectroscopy or RIPES. Here, we report the observation of RIPES in an f electron system, specifically the at the 3d{sub 5/2} and 3d{sub 3/2} thresholds of Ce Oxide. The resonant behavior of the Ce4f structure at the 3d thresholds has been addressed before, including studies of the utilization of the technique as a probe of electron correlation in a variety of Ce compounds. Interestingly, the first RIPES work on rare earths dates back to 1974, although under conditions which left the state of the surface and near surface regions undefined. Although they did not use the more modern terminology of 'RIPES,' it is clear that RIPES was actually first performed in 1974 by Liefeld, Burr and Chamberlain on both La and Ce based

  8. A proposed new scheme for vibronically resolved time-dependent photoelectron spectroscopy: pump-repump-continuous wave-photoelectron spectroscopy (prp-cw-pes).

    Science.gov (United States)

    Goel, Prateek; Nooijen, Marcel

    2016-04-20

    We propose a new scheme for time-resolved photoelectron spectroscopy denoted as pump-repump-continuous wave-photoelectron spectroscopy (prp-cw-pes). This scheme is comprised of two femtosecond laser (pump) pulses under cw illumination (probe). By changing the time-delay between pump and repump lasers one can manipulate the populations of vibronic levels in electronic excited states. The cw laser acts on for a long time and establishes resonance between excited states and the continuum photo-ionized states. Sharp spectra can be obtained from the resonance condition . The intensities in the spectra are sensitive to the time-delay between the pump-repump pulses, but only depend on the populations of excited states, not the phase relations (coherence). As a result, each time-delayed snapshot spectrum is a weighted sum of so-called fingerprints, where a fingerprint is the vibrationally resolved photoelectron spectrum for a single vibronic excited state. The latter information can potentially be simulated reliably using vibronic models and wave packet propagation methods. In the easiest application of the experiment, different time-delays produce different spectra, for a single molecular system. This wealth of experimental data can be fitted to an, ideally small, set of theoretical fingerprints by adjusting the populations as fitting parameters. This technique might be able to distinguish between closely related molecular species. Adopting a different viewpoint, the proposed scheme can also be employed to monitor the time-dependent dynamics by changing the phase relationship between the pump and repump laser that can be viewed as a "control mechanism" employed in wave packet interferometry. Simplifications arise as the change in the spectra is due to the changing populations, not because of the coherence. In this paper, we outline the ideas behind the scheme and illustrate the ideas theoretically using simple model systems. PMID:27052895

  9. High-throughput toroidal grating beamline for photoelectron spectroscopy at CAMD

    International Nuclear Information System (INIS)

    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/100 mA) 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.

  10. Understanding interface properties from high kinetic energy photoelectron spectroscopy and first principles theory

    International Nuclear Information System (INIS)

    Advances in instrumentation regarding 3rd generation synchrotron light sources and electron spectrometers has enabled the field of high kinetic energy photoelectron spectroscopy (HIKE) (also often denoted hard X-ray photoelectron spectroscopy (HX-PES or HAXPES)). Over the last years, the amount of investigations that relies on the HIKE method has increased dramatically and can arguably be said to have given a rebirth of the interest in photoelectron spectroscopy in many areas. It is in particular the much increased mean free path at higher kinetic energies in combination with the elemental selectivity of the core level spectroscopies in general that has lead to this fact, as it makes it possible to investigate the electronic structure of materials with a substantially reduced surface sensitivity. In this review we demonstrate how HIKE can be used to investigate the interface properties in multilayer systems. Relative intensities of the core level photoelectron peaks and their chemical shifts derived from binding energy changes are found to give precise information on physico-chemical properties and quality of the buried layers. Interface roughening, including kinetic properties such as the rate of alloying, and temperature effects on the processes can be analyzed quantitatively. We will also provide an outline of the theoretical framework that is used to support the interpretation of data. We provide examples from our own investigations of multilayer systems which comprises both systems of more model character and a multilayer system very close to real applications in devices that are considered to be viable alternative to the present read head technology. The experimental data presented in this review is exclusively recorded at the BESSY-II synchrotron at the Helmholtz-Zentrum Berlin fuer Materialien und Energie. This HIKE facility is placed at the bending magnet beamline KMC-1, which makes it different from several other facilities which relies on undulators as

  11. Understanding interface properties from high kinetic energy photoelectron spectroscopy and first principles theory

    Energy Technology Data Exchange (ETDEWEB)

    Granroth, Sari [Department of Physics and Astronomy, University of Turku, FIN-20014 Turku (Finland); Department of Physics and Materials Science, Uppsala University, SE-751 21 Uppsala (Sweden); Olovsson, Weine [Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan); Holmstroem, Erik [Instituto de Fisica, Universidad Austral de Chile, Valdivia (Chile); Knut, Ronny [Department of Physics and Materials Science, Uppsala University, SE-751 21 Uppsala (Sweden); Gorgoi, Mihaela [Helmholtz Zentrum Berlin, BESSY II, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Svensson, Svante [Department of Physics and Materials Science, Uppsala University, SE-751 21 Uppsala (Sweden); Karis, Olof, E-mail: olof.karis@fysik.uu.s [Department of Physics and Materials Science, Uppsala University, SE-751 21 Uppsala (Sweden)

    2011-01-15

    Advances in instrumentation regarding 3rd generation synchrotron light sources and electron spectrometers has enabled the field of high kinetic energy photoelectron spectroscopy (HIKE) (also often denoted hard X-ray photoelectron spectroscopy (HX-PES or HAXPES)). Over the last years, the amount of investigations that relies on the HIKE method has increased dramatically and can arguably be said to have given a rebirth of the interest in photoelectron spectroscopy in many areas. It is in particular the much increased mean free path at higher kinetic energies in combination with the elemental selectivity of the core level spectroscopies in general that has lead to this fact, as it makes it possible to investigate the electronic structure of materials with a substantially reduced surface sensitivity. In this review we demonstrate how HIKE can be used to investigate the interface properties in multilayer systems. Relative intensities of the core level photoelectron peaks and their chemical shifts derived from binding energy changes are found to give precise information on physico-chemical properties and quality of the buried layers. Interface roughening, including kinetic properties such as the rate of alloying, and temperature effects on the processes can be analyzed quantitatively. We will also provide an outline of the theoretical framework that is used to support the interpretation of data. We provide examples from our own investigations of multilayer systems which comprises both systems of more model character and a multilayer system very close to real applications in devices that are considered to be viable alternative to the present read head technology. The experimental data presented in this review is exclusively recorded at the BESSY-II synchrotron at the Helmholtz-Zentrum Berlin fuer Materialien und Energie. This HIKE facility is placed at the bending magnet beamline KMC-1, which makes it different from several other facilities which relies on undulators as

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

    OpenAIRE

    Ahmed, Marawan; Wang, Feng; 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 agreeme...

  13. Parent Anions of Iron, Manganese, and Nickel Tetraphenyl Porphyrins: Photoelectron Spectroscopy and Computations.

    Science.gov (United States)

    Buytendyk, Allyson M; Graham, Jacob D; Gould, Julian; Bowen, Kit H

    2015-08-13

    The singly charged, parent anions of three transition metal, tetraphenyl porphyrins, M(TPP) [Fe(TPP), Mn(TPP), and Ni(TPP)], were studied by negative ion photoelectron spectroscopy. The observed (vertical) transitions from the ground state anions of these porphyrins to the various electronic states of their neutral counterparts were modeled by density functional theory computations. Our experimental and theoretical results were in good agreement. PMID:26186172

  14. Depth Profiling of the Passive Layer on Stainless Steel using Photoelectron Spectroscopy

    OpenAIRE

    Fredriksson, Wendy

    2012-01-01

    The physical properties of the protective passive films formed on the surface of stainless steels under electrochemical polarization in different electrolytes were studied. The structure of these films was analyzed as a function of depth using photoelectron spectroscopy (PES). Depth profiling (using PES) of the surface layer was achieved by either changing the angle of incidence to achieve different analysis depths (ARXPS), by argon ion etching, or by varying the energy of the incoming x-rays...

  15. A Photoelectron Spectroscopy and ab initio Study of B3- and B4- Anions and Their Neutrals

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Hua-Jin; Wang, Lai S.; Alexandrova, A N.; Boldyrev, Alexander I.; Zakrzewski, V G.

    2003-11-06

    The two smallest boron clusters (B3 and B4) in their neutral and anionic forms were studied by photoelectron spectroscopy and ab initio calculations. Vibrationally resolved photoelectron spectra were observed for B3- at three photon energies (355, 266, and 193 nm) and the electron affinity of B3 was measured to be+0.02 eV.

  16. X-ray photoelectron spectroscopy and positron annihilation spectroscopy analysis of surfactant affected FePt spintronic films

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Chun, E-mail: fengchun@ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Li, Xujing; Liu, Fen; Wang, Qiang [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yang, Meiyin [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); The Center for Micromagnetics and Information Technologies (MINT) and Department of Electrical and Computer Engineering, University of Minnesota, 200 Union St SE, Minneapolis, MN 55455 (United States); Zhao, Chongjun [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Gong, Kui [Centre for the Physics of Materials and Department of Physics, McGill University, Montreal, Quebec, H3A2T8 Canada (Canada); Zhang, Peng; Wang, Bao-Yi; Cao, Xing-Zhong [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Yu, Guanghua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2014-07-01

    This paper reports the effects of surfactant Bi atomic diffusion on the microstructure evolution and resulted property manipulation in FePt spintronic films by the quantitative studies of X-ray photoelectron spectroscopy and positron annihilation spectroscopy. The defect density in the FePt layer, which was tunable by varying the thermal treatment temperatures, was found to be remarkably enhanced correlated with the Bi atomic diffusion behavior. The observed defect density evolution substantially favors Fe(Pt) atomic migrations and lowers the energy barrier for atomic ordering transition, resulting in a great improvement of hard magnet property of the films.

  17. Threshold photoelectron spectroscopy and photoionization total ion yield spectroscopy of simple organic acids, aldehydes, ketones and amines

    International Nuclear Information System (INIS)

    We have initiated a research program to investigate the ionization behavior of some simple organic molecules containing the carboxyl group (R2C=O), where R could be H, OH, NH2, or CH3 or other aliphatic or aromatic carbon groups, using threshold photoelectron spectroscopy and photoionization total ion yield spectroscopy. We report here on the simplest organic acid, formic acid, and two simple aldehydes: acetaldehyde and the simplest unsaturated aldehyde, 2-propenal (acrolein). The objective of this study was to characterize the valence cationic states of these molecules with vibrational structural resolution.

  18. Photoelectron yield spectroscopy and inverse photoemission spectroscopy evaluations of p-type amorphous silicon carbide films prepared using liquid materials

    Directory of Open Access Journals (Sweden)

    Tatsuya Murakami

    2016-05-01

    Full Text Available Phosphorus-doped amorphous silicon carbide films were prepared using a polymeric precursor solution. Unlike conventional polymeric precursors, this polymer requires neither catalysts nor oxidation for its synthesis and cross-linkage, providing semiconducting properties in the films. The valence and conduction states of resultant films were determined directly through the combination of inverse photoemission spectroscopy and photoelectron yield spectroscopy. The incorporated carbon widened energy gap and optical gap comparably in the films with lower carbon concentrations. In contrast, a large deviation between the energy gap and the optical gap was observed at higher carbon contents because of exponential widening of the band tail.

  19. X-ray photoelectron spectroscopy and positron annihilation spectroscopy analysis of surfactant affected FePt spintronic films

    International Nuclear Information System (INIS)

    This paper reports the effects of surfactant Bi atomic diffusion on the microstructure evolution and resulted property manipulation in FePt spintronic films by the quantitative studies of X-ray photoelectron spectroscopy and positron annihilation spectroscopy. The defect density in the FePt layer, which was tunable by varying the thermal treatment temperatures, was found to be remarkably enhanced correlated with the Bi atomic diffusion behavior. The observed defect density evolution substantially favors Fe(Pt) atomic migrations and lowers the energy barrier for atomic ordering transition, resulting in a great improvement of hard magnet property of the films.

  20. Pb 4f photoelectron spectroscopy on mass-selected anionic lead clusters at FLASH

    International Nuclear Information System (INIS)

    4f core level photoelectron spectroscopy has been performed on negatively charged lead clusters, in the size range of 10-90 atoms. We deploy 4.7 nm radiation from the free-electron laser FLASH, yielding sufficiently high photon flux to investigate mass-selected systems in a beam. A new photoelectron detection system based on a hemispherical spectrometer and a time-resolving delayline detector makes it possible to assign electron signals to each micro-pulse of FLASH. The resulting 4f binding energies show good agreement with the metallic sphere model, giving evidence for a fast screening of the 4f core holes. By comparing the present work with previous 5d and valence region data, the paper presents a comprehensive overview of the energetics of lead clusters, from atoms to bulk. Special care is taken to discuss the differences of the valence- and core-level anion cluster photoionizations. Whereas in the valence case the escaping photoelectron interacts with a neutral system near its ground state, core-level ionization leads to transiently highly excited neutral clusters. Thus, the photoelectron signal might carry information on the relaxation dynamics. (paper)

  1. 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.

  2. Study of low-lying electronic states of ozone by anion photoelectron spectroscopy of O - 3

    Science.gov (United States)

    Arnold, Don W.; Xu, Cangshan; Kim, Eun H.; Neumark, Daniel M.

    1994-07-01

    The low-lying electronic states of ozone are studied using anion photoelectron spectroscopy of O-3. The spectra show photodetachment transitions from O-3 to the X˜ 1A1 ground state and to the five lowest lying electronic states of the ozone molecule, namely the 3A2, 3B2, 1A2, 3B1, and 1B1 states. The geometry of the ozonide anion determined from a Franck-Condon analysis of the O3 X 1A1 ground state spectrum agrees reasonably well with previous work. The excited state spectra are dominated by bending vibrational progressions which, for some states, extend well above the dissociation asymptote without noticeable lifetime broadening effects. Preliminary assignments are based upon photoelectron angular distributions and comparison with ab initio calculations. None of the excited states observed lies below the ground state dissociation limit of O3 as suggested by previous experimental and theoretical results.

  3. X-ray photoelectron spectroscopy investigations of zinc-magnesium alloy coated steel

    International Nuclear Information System (INIS)

    The coating layer composition depth profiles and element chemical states of zinc-magnesium alloy coated steel were investigated by X-ray photoelectron spectroscopy depth profiling. Through the analysis of photoelectron signals and Auger signals of different elements on different depth planes of the coating layer, it can be found that the surface of the coating layer contains MgCO3, MgO, Mg(OH)2, metallic Mg, metallic Zn and some complex zinc compounds. Under the surface, there is a Zn2Mg alloy layer with the thickness of about 300 nm accompanied with MgO and Mg(OH)2 in the layer. There is a transitional layer with the thickness of about 200 nm between the Zn2Mg alloy layer and the pure Zn layer, whose components consist of zinc-magnesium alloy without fixed stoichiometry, a little MgO and a little Mg(OH)2.

  4. 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.

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

    International Nuclear Information System (INIS)

    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. First, aerosol photoemission studies can be performed for many different materials, including liquids. Second, 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

  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 (<300 eV) where the ad hoc method systematically underestimates the preferential enhancement of anions over cations. Finally, some technical aspects of applying SESSA to liquid interfaces are discussed.

  7. Small molecule photoelectron spectroscopy: Recoil effects, stoichiometric surprises, and double-core-hole ionization

    International Nuclear Information System (INIS)

    Highlights: ► The effects of recoil momentum on a photoelectron spectrum are illustrated. ► Rotational motion within a molecule leads to Doppler broadening in the XPS spectrum. ► Intensities in an XPS spectrum may not quantitatively reflect molecule composition. ► Measurement of double-core-hole-ionization energies may lead to new insights. -- Abstract: Three features of small-molecule photoelectron spectroscopy are considered (1) the atom from which a photoelectron is emitted must have a recoil momentum equal to that of the emitted electron. This is shared among the various modes of motion of the ion, leading to rotational and vibrational excitation. Furthermore, any initial velocity of the atom (due to either translational, rotational, or vibrational motion) will lead to Doppler broadening. These effects are observable and can, in general, be accounted for by simple models. In some cases, however, the simple models fail and a deeper insight is necessary. (2) Inner-shell photoionization is essentially an atomic process, and it is expected that the intensity for emission of a photoelectron from the core of an atom in a molecule will be independent of its chemical environment. Recent measurements on the carbon 1s photoelectron spectra of three chloroethanes show that this is not the case. At energies not far above the ionization threshold there are strong oscillations of the intensity ratio (CCl/CH) with increasing photon energy. These are similar to those seen in EXAFS and can be accounted for by considering backscattering of the photoelectrons from the chlorine atoms. Moreover, even at high energies the cross section for ionization has been found to depend on the chemical environment of the atom. These results have important consequences for the use of inner-shell electron spectroscopy for quantitative analysis. (3) Single-core-hole ionization energies have long been used as a tool for investigating chemical phenomena. Double-core-hole ionization energies

  8. Ultrafast soft X-ray photoelectron spectroscopy at liquid water microjets.

    Science.gov (United States)

    Faubel, M; Siefermann, K R; Liu, Y; Abel, B

    2012-01-17

    Since the pioneering work of Kai Siegbahn, electron spectroscopy for chemical analysis (ESCA) has been developed into an indispensable analytical technique for surface science. The value of this powerful method of photoelectron spectroscopy (PES, also termed photoemission spectroscopy) and Siegbahn's contributions were recognized in the 1981 Nobel Prize in Physics. The need for high vacuum, however, originally prohibited PES of volatile liquids, and only allowed for investigation of low-vapor-pressure molecules attached to a surface (or close to a surface) or liquid films of low volatility. Only with the invention of liquid beams of volatile liquids compatible with high-vacuum conditions was PES from liquid surfaces under vacuum made feasible. Because of the ubiquity of water interfaces in nature, the liquid water-vacuum interface became a most attractive research topic, particularly over the past 10 years. PES studies of these important aqueous interfaces remained significantly challenging because of the need to develop high-pressure PES methods. For decades, ESCA or PES (termed XPS, for X-ray photoelectron spectroscopy, in the case of soft X-ray photons) was restricted to conventional laboratory X-ray sources or beamlines in synchrotron facilities. This approach enabled frequency domain measurements, but with poor time resolution. Indirect access to time-resolved processes in the condensed phase was only achieved if line-widths could be analyzed or if processes could be related to a fast clock, that is, reference processes that are fast enough and are also well understood in the condensed phase. Just recently, the emergence of high harmonic light sources, providing short-wavelength radiation in ultrashort light pulses, added the dimension of time to the classical ESCA or XPS technique and opened the door to (soft) X-ray photoelectron spectroscopy with ultrahigh time resolution. The combination of high harmonic light sources (providing radiation with laserlike

  9. 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.

  10. Adsorption of NO2 on WSe2: DFT and photoelectron spectroscopy studies.

    Science.gov (United States)

    Ovcharenko, R; Dedkov, Yu; Voloshina, E

    2016-09-14

    The electronic structure modifications of WSe2 upon NO2-adsorption at room and low temperatures were studied by means of photoelectron spectroscopy. We found only moderate changes in the electronic structure, which are manifested as an upward shift of the WSe2-related bands to the smaller binding energies. The observed effects are modelled within the density functional theory approach, where a small adsorption energy of gas molecules on the surface of WSe2 was deduced. The obtained experimental data are explained as a valence bands polarisation effect, which causes their energy shift depending on the adsorption geometry and the formed dipole moment. PMID:27392163

  11. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    OpenAIRE

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; LIU, ZHI; Shao-Horn, Yang

    2012-01-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+x Ti5O12/LiPON/Li x V2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, ...

  12. X-ray photoelectron spectroscopy study of synchrotron radiation irradiation of a polytetrafluoroethylene surface

    CERN Document Server

    Haruyama, Y; Matsui, S; Ideta, T; Ishigaki, H

    2003-01-01

    The effect of synchrotron radiation (SR) irradiation of a polytetrafluoroethylene (PTFE) surface was investigated using X-ray photoelectron spectroscopy (XPS). After the SR irradiation, the relative intensity of the F ls peak to the C ls peak decreased markedly. The chemical composition ratio to the F atoms to C atoms was estimated to be 0.29. From the curve fitting analysis of C ls and F ls XPS spectra, the chemical components and their intensity ratio were determined. The reason for the chemical composition change by the SR irradiation was discussed. (author)

  13. Energy band alignment at ferroelectric/electrode interface determined by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The most important interface-related quantities determined by band alignment are the barrier heights for charge transport, given by the Fermi level position at the interface. Taking Pb(Zr,Ti)O3 (PZT) as a typical ferroelectric material and applying X-ray photoelectron spectroscopy (XPS), we briefly review the interface formation and barrier heights at the interfaces between PZT and electrodes made of various metals or conductive oxides. Polarization dependence of the Schottky barrier height at a ferroelectric/electrode interface is also directly observed using XPS. (topical review - magnetism, magnetic materials, and interdisciplinary research)

  14. Contact-free pyroelectric measurements using x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Non-contact pyroelectricity measurements based on x-ray photoelectron spectroscopy (XPS) are presented. Applied to Lithium Tantalate crystals, we demonstrate how the XPS-derived surface potential provides a simple probe of the desired property, free of all top-contact related difficulties. In particular, the increase in Lithium Tantalate spontaneous polarization under cooling, an experimentally challenging feature, is evaluated. We further inspect the roll of surface contaminants and the control over trapped surface charge in the XPS vacuum environment. Our approach can be extended to other non-contact probes, as well as to measuring additional electrical properties, such as piezoelectricity and ferroelectricity

  15. Contact-free pyroelectric measurements using x-ray photoelectron spectroscopy

    Science.gov (United States)

    Ehre, D.; Cohen, H.

    2013-07-01

    Non-contact pyroelectricity measurements based on x-ray photoelectron spectroscopy (XPS) are presented. Applied to Lithium Tantalate crystals, we demonstrate how the XPS-derived surface potential provides a simple probe of the desired property, free of all top-contact related difficulties. In particular, the increase in Lithium Tantalate spontaneous polarization under cooling, an experimentally challenging feature, is evaluated. We further inspect the roll of surface contaminants and the control over trapped surface charge in the XPS vacuum environment. Our approach can be extended to other non-contact probes, as well as to measuring additional electrical properties, such as piezoelectricity and ferroelectricity.

  16. X-ray Photoelectron Spectroscopy Studies of MgB2 for Valence State of Mg

    OpenAIRE

    Talapatra, A.; Bandyopadhyay, S K; Sen, Pintu; P. Barat; S. Mukherjee; Mukherjee, M.(Variable Energy Cyclotron Centre, Kolkata, India)

    2004-01-01

    Core level X-ray Photoelectron Spectroscopy (XPS) studies have been carried out on polycrystalline MgB_2 pellets over the whole binding energy range with a view to having an idea of the charge state of Magnesium (Mg). We observe 3 distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB_2 and MgCO_3 or, divalent Mg species respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB_2 is lower ...

  17. Ionization of aqueous cations: Photoelectron spectroscopy and ab initio calculations of protonated imidazole

    Czech Academy of Sciences Publication Activity Database

    Jagoda-Cwiklik, Barbara; Slavíček, P.; Nolting, D.; Winter, B.; Jungwirth, Pavel

    2008-01-01

    Roč. 112, č. 25 (2008), s. 7355-7358. ISSN 1520-6106 R&D Projects: GA MŠk LC512; GA ČR GA203/07/1006 Grant ostatní: DFG(DE) WI1327/3-1; GA ČR(CZ) GP203/07/P449 Institutional research plan: CEZ:AV0Z40550506 Keywords : protenated imidazole * ab initio calculations * photoelectron spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.189, year: 2008

  18. 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.

  19. Electronic structure and thermal decomposition of 5-aminotetrazole studied by UV photoelectron spectroscopy and theoretical calculations

    International Nuclear Information System (INIS)

    Graphical abstract: Gas-phase UV photoelectron spectrum of the thermal decomposition of 5-aminotetrazole (5ATZ), obtained at 245 oC, and mechanism underlying the thermal dissociation of 2H-5ATZ. Research highlights: → Electronic structure of 5ATZ studied by photoelectron spectroscopy. → Gas-phase 5-ATZ exists mainly as the 2H-tautomer. → Thermal decomposition of 5ATZ gives N2, NH2CN, HN3 and HCN, at 245 oC. → HCN can be originated from a carbene intermediate. - Abstract: The electronic properties and thermal decomposition of 5-aminotetrazole (5ATZ) are investigated using UV photoelectron spectroscopy (UVPES) and theoretical calculations. Simulated spectra of both 1H- and 2H-5ATZ, based on electron propagator methods, are produced in order to study the relative gas-phase tautomer population. The thermal decomposition results are rationalized in terms of intrinsic reaction coordinate (IRC) calculations. 5ATZ yields a HOMO ionization energy of 9.44 ± 0.04 eV and the gas-phase 5ATZ assumes mainly the 2H-form. The thermal decomposition of 5ATZ leads to the formation of N2, HN3 and NH2CN as the primary products, and HCN from the decomposition of a intermediate CH3N3 compound. The reaction barriers for the formation of HN3 and N2 from 2H-5ATZ are predicted to be ∼228 and ∼150 kJ/mol, at the G2(MP2) level, respectively. The formation of HCN and HNNH from the thermal decomposition of a CH3N3 carbene intermediate is also investigated.

  20. Photoelectron spectroscopy study of metallic nanocluster arrangement at the surface of reactively sputtered amorphous hydrogenated carbon

    International Nuclear Information System (INIS)

    We report on the results of the arrangement of isolated surface metallic nanoclusters embedded in amorphous hydrogenated carbon (a-C:H) thin films, studied by photoelectron spectroscopy. As a model system we used gold-containing amorphous hydrogenated carbon (a-C:H/Au), due to the lack of reactivity between carbon and gold. The a-C:H/Au samples are obtained by simultaneous magnetron sputtering of Au target by argon and plasma-enhanced chemical vapor deposition of methane. Photoelectron spectroscopy with x-ray and ultraviolet excitation has been employed for surface studies that comprise as-deposited sample spectra recordings, measurements at off-normal takeoff angle, in situ in-depth profiling by Ar+ ion etching, and thiophene adsorption at the sample surface. The results of these extended studies firmly support previously drawn conclusions [I. R. Videnovic, V. Thommen, P. Oelhafen, D. Mathys, M. Dueggelin, and R. Guggenheim, Appl. Phys. Lett 80, 2863 (2002)] that by deposition on electrically grounded substrates one obtains samples with topmost Au clusters covered with a thin layer of a-C:H. Introducing a dc substrate bias voltage results in bald Au clusters on the surface and increased sp2/sp3 coordinated carbon ratio in the a-C:H matrix

  1. Soft x-ray photoelectron spectroscopy study of type-I clathrates

    Directory of Open Access Journals (Sweden)

    Jun Tang, Zhaofei Li, Jing Ju, Ryotaro Kumashiro, Marcos A. Avila, Kouichirou Suekuni, Toshiro Takabatake, FangZhun Guo, Keisuke Kobayashi, Koji Akai and Katsumi Tanigaki

    2008-01-01

    Full Text Available Extensive soft x-ray photoelectron spectroscopy studies are performed on Ba8 Ga16 Ge30 (BGG and Sr8Ga16Ge30 (SGG single crystals ranging from Fermi to core levels, at a high-energy facility. Valence band x-ray photoelectron spectroscopy (XPS experiments with theoretical calculations revealed that the valence band is mainly constructed by the Ge/Ga 4s and 4p wave functions with little contribution of the Ba/Sr atomic orbitals. Surprisingly, unexpected features evidencing the different shift for the 2a- and 6d- sites between Ba 4d and Sr 3d are observed. The detailed analyses including theoretical support by first-principles band-structure calculations lead to the conclusion that the component distributions of the larger tetrakaidecahedral cage are different depending on the endohedral atoms, which contrasts with the past consensus that BGG and SGG have the same framework structure. This may give thorough reconsiderations on earlier interpretations of experimental data.

  2. 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.

  3. 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.

  4. X-ray photoelectron spectroscopy characterization of the ω phase in water quenched Ti-5553 alloy

    International Nuclear Information System (INIS)

    X-ray photoelectron spectroscopy was used to investigate the ω phase in water quenched Ti-5553 alloy with a nominal composition of Ti–5Al–5V–5Mo–3Cr (wt.%), and the ω and the β phase were distinguished by deconvoluting the XPS spectra of Al2p, V2p and Cr2p core level regions. In addition, it is found that the binding energy of core level electron of alloying elements shifts comparing with that of pure metals, and the fact was interpreted by charge redistribution model. X-ray photoelectron spectroscopy technique could be used to characterize the nano-scale ω phase in β alloys. - Highlights: ► We characterize the ω phase in Ti-5553 alloy by XPS. ► Binding energy of Al2p, V2p and Cr2p electron are different in the ω and β phase. ► Structural difference leads to the binding energy gap.

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

    International Nuclear Information System (INIS)

    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

  6. Resonance-enhanced multiphoton ionization photoelectron spectroscopy of Rydberg states of N2O below the X ionization limit

    OpenAIRE

    Scheper, C.R.; Kuijt, J.; Buma, W.J.; Lange

    1998-01-01

    A three-photon resonance-enhanced multiphoton ionization spectroscopic study on N2O is carried out in the spectral range from 80 000 cm - 1 up to the lowest ionization limit at 103 963 cm - 1. High-resolution photoelectron spectroscopy is used to identify and characterize the observed excited states. Eighteen origins are reported which have either not been assigned before or are reassigned now. Moreover, the photoelectron spectra taken at higher-lying resonances often show extensive vibronic ...

  7. Direct experimental observation of the low ionization potentials of guanine in free oligonucleotides by using photoelectron spectroscopy

    OpenAIRE

    Yang, Xin; Wang, Xue-Bin; Vorpagel, Erich R.; Wang, Lai-Sheng

    2004-01-01

    Photodetachment photoelectron spectroscopy is used to probe the electronic structure of mono-, di-, and trinucleotide anions in the gas phase. A weak and well defined threshold band was observed in the photoelectron spectrum of 2′-deoxyguanosine 5′-monophosphate at a much lower ionization energy than the other three mononucleotides. Density function theory calculations revealed that this unique spectral feature is caused by electron-detachment from a π orbital of the guanine base on 2′-deoxyg...

  8. Secondary electron imaging of nanostructures using Extreme Ultra-Violet attosecond pulse trains and Infra-Red femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Maarsell, Erik; Arnold, Cord L.; Lorek, Eleonora; Guenot, Diego; Fordell, Thomas; Miranda, Miguel; Mauritsson, Johan; Xu, Hongxing; L' Huillier, Anne; Mikkelsen, Anders [Department of Physics, Lund University, Box 118, 221 00 Lund (Sweden)

    2013-02-15

    Surface electron dynamics unfold at time and length scales down to attoseconds and nanometres, making direct imaging with extreme spatiotemporal resolution highly desirable. However, this has turned out to be a major challenge even with the advent of reliable attosecond light sources. In this paper, photoelectrons from Ag nanowires and nanoparticles excited by extreme ultraviolet (XUV) attosecond pulse trains and infrared femtosecond pulses using a PhotoEmission Electron Microscope (PEEM) are imaged. In addition, the samples were investigated using Scanning Electron Microscopy (SEM) and synchrotron based X-ray photoelectron spectroscopy (XPS). To achieve contrast between the nanostructures and the substrate in the XUV images, three different substrate materials were investigated: Cr, ITO and Au. While plasmonic field enhancement can be observed on all three substrates, only on Au substrates do the Ag nanowires appear significantly brighter than the substrate in XUV-PEEM imaging. 3-photon photoemission imaging of plasmonic hot-spots was performed where the autocorrelation trace is observed in the interference signal between two femtosecond Infra-Red (IR) beams with sub-cycle precision. Finally, using Monte Carlo simulations, it is shown how the secondary electrons imaged in the XUV PEEM can potentially reveal information on the attosecond time scale from the near surface region of the nanostructures. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Very low energy photoelectron spectroscopy in multiphoton ionization of H2

    OpenAIRE

    Bordas, C.; Dyer, M.; Helm, H.

    1994-01-01

    We apply a novel photoelectron imaging spectrometer [1] to the energy and angular analysis of photoelectrons resulting from resonantly enhanced multiphoton ionization of H2. Photoelectron images with well resolved individual rotational structure of the resulting H2+ ion are obtained, demonstrating the capability of this technique for analyzing photoelectrons in the meV energy range.

  10. Attosecond-resolved electron dynamics around the 1st ionization threshold of helium measured by multidimensional absorption spectroscopy

    International Nuclear Information System (INIS)

    We recently developed a transient-coupling measurement scheme, which we employed to uncover coherent laser-induced coupling of doubly-excited helium states to continuum states. Here, we apply this measurement scheme to study in detail the coherent electron dynamics and general absorption phenomena arising for single-excitation of helium around 24 eV with attosecond-pulsed VUV light fields. Exploiting a multidimensional control by (a) varying the time delay between the attosecond and a coupling laser pulse, (b) tuning the coupling laser intensity and (c) analyzing the propagation direction of the transmitted VUV attosecond pulse we observe the transformation of the original (Lorentzian) resonance shapes into Fano line shapes. To understand the mechanism behind this quantum control we performed numerical simulations to model our experimental results, which include the attosecond-pulsed excitation and laser coupling of multiple excited states. These simulations allowed us to identify the ponderomotive dressing of the states in the laser field as a key component for understanding the control of several line shapes of the observed absorption spectra.

  11. Attosecond-resolved electron dynamics around the 1st ionization threshold of helium measured by multidimensional absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kaldun, Andreas; Ott, Christian; Stooss, Veit; Raith, Philipp; Meyer, Kristina; Laux, Martin; Blaettermann, Alexander; Ding, Thomas; Pfeifer, Thomas [Max-Planck Institut f. Kernphysik, Heidelberg (Germany)

    2013-07-01

    We recently developed a transient-coupling measurement scheme, which we employed to uncover coherent laser-induced coupling of doubly-excited helium states to continuum states. Here, we apply this measurement scheme to study in detail the coherent electron dynamics and general absorption phenomena arising for single-excitation of helium around 24 eV with attosecond-pulsed VUV light fields. Exploiting a multidimensional control by (a) varying the time delay between the attosecond and a coupling laser pulse, (b) tuning the coupling laser intensity and (c) analyzing the propagation direction of the transmitted VUV attosecond pulse we observe the transformation of the original (Lorentzian) resonance shapes into Fano line shapes. To understand the mechanism behind this quantum control we performed numerical simulations to model our experimental results, which include the attosecond-pulsed excitation and laser coupling of multiple excited states. These simulations allowed us to identify the ponderomotive dressing of the states in the laser field as a key component for understanding the control of several line shapes of the observed absorption spectra.

  12. Electronic Structures of Uranium Compounds Studied by Soft X-ray Photoelectron Spectroscopy

    Science.gov (United States)

    Fujimori, Shin-ichi; Takeda, Yukiharu; Okane, Tetsuo; Saitoh, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Ōnuki, Yoshichika

    2016-06-01

    The electronic structures of uranium-based compounds have been studied by photoelectron spectroscopy with soft X-ray synchrotron radiation. Angle-resolved photoelectron spectroscopy with soft X-rays has made it possible to directly observe their bulk band structures and Fermi surfaces. It has been shown that the band structures and Fermi surfaces of itinerant compounds such as UB2, UN, and UFeGa5 are quantitatively described by a band-structure calculation treating all U 5f electrons as itinerant. Furthermore, the overall electronic structures of heavy-fermion compounds such as UPd2Al3, UNi2Al3, and URu2Si2 are also explained by a band-structure calculation, although some disagreements exist, which might originate from the electron correlation effect. This suggests that the itinerant description of U 5f states is an appropriate starting point for the description of their electronic structures. The situation is similar for ferromagnetic superconductors such as UGe2, URhGe, UCoGe, and UIr, although the complications from their low-symmetry crystal structures make it more difficult to describe their detailed electronic structures. The local electronic structures of the uranium site have been probed by core-level photoelectron spectroscopy with soft X-rays. The comparisons of core-level spectra of heavy-fermion compounds with typical itinerant and localized compounds suggest that the local electronic structures of most itinerant and heavy-fermion compounds are close to the U 5f3 configuration except for UPd2Al3 and UPt3. The core-level spectrum of UPd2Al3 has similarities to those of both itinerant and localized compounds, suggesting that it is located at the boundary between the itinerant and localized states. Moreover, the spectrum of UPt3 is very close to that of the localized compound UPd3, suggesting that it is nearly localized, although there are narrow quasi-particle bands in the vicinity of EF.

  13. Versatile attosecond beamline in a two-foci configuration for simultaneous time-resolved measurements

    Energy Technology Data Exchange (ETDEWEB)

    Locher, R.; Lucchini, M., E-mail: mlucchini@phys.ethz.ch; Herrmann, J.; Sabbar, M.; Weger, M.; Ludwig, A.; Gallmann, L.; Keller, U. [Department of Physics, ETH Zurich, CH-8093 Zürich (Switzerland); Castiglioni, L.; Greif, M.; Hengsberger, M. [Institute of Physics, University of Zurich, CH-8057 Zürich (Switzerland)

    2014-01-15

    We present our attoline which is a versatile attosecond beamline at the Ultrafast Laser Physics Group at ETH Zurich for attosecond spectroscopy in a variety of targets. High-harmonic generation (HHG) in noble gases with an infrared (IR) driving field is employed to generate pulses in the extreme ultraviolet (XUV) spectral regime for XUV-IR cross-correlation measurements. The IR pulse driving the HHG and the pulse involved in the measurements are used in a non-collinear set-up that gives independent access to the different beams. Single attosecond pulses are generated with the polarization gating technique and temporally characterized with attosecond streaking. This attoline contains two target chambers that can be operated simultaneously. A toroidal mirror relay-images the focus from the first chamber into the second one. In the first interaction region a dedicated double-target allows for a simple change between photoelectron/photoion measurements with a time-of-flight spectrometer and transient absorption experiments. Any end station can occupy the second interaction chamber. A surface analysis chamber containing a hemispherical electron analyzer was employed to demonstrate successful operation. Simultaneous RABBITT measurements in two argon jets were recorded for this purpose.

  14. Direct XUV Probing of Attosecond Electron Recollision

    International Nuclear Information System (INIS)

    We demonstrate that the recolliding electron wave packet, fundamental to many strong field phenomena, can be directly imaged with sub-A spatial and attosecond temporal resolution using attosecond extreme ultraviolet (XUV) pulses. When the recolliding electron revisits the parent ion, it can absorb an XUV photon yielding high energy electron and thereby providing a measurement of the electron energy at the moment of recollision. The full temporal evolution of the recollision wave packet can be reconstructed by measuring the photoelectron spectra for different time delays between the driving laser and the attosecond XUV probe. The strength of the photoelectron signal can be used to characterize the spatial distribution of the electron density in the longitudinal direction. Elliptical polarization can be used to characterize the electron probability in transversal direction

  15. Ultrafast XUV Pulses at High Repetition Rate for Time Resolved Photoelectron Spectroscopy of Surface Dynamics

    Science.gov (United States)

    Corder, Christopher; Zhao, Peng; Li, Xinlong; Muraca, Amanda R.; Kershis, Matthew D.; White, Michael G.; Allison, Thomas K.

    2016-05-01

    Ultrafast photoelectron studies of surface dynamics are often limited by low repetition rates. At Stony Brook we have built a cavity-enhanced high-harmonic generation XUV source that delivers ultrafast pulses to a surface science apparatus for photoelectron spectroscopy. We begin with a Ytterbium fiber laser at a repetition rate of 78 MHz and up to 90 W of average power. After compression the pulses have μJ's of energy with high harmonic generation. The enhancement cavity is a six mirror double folded bow-tie geometry with a focus of 15 μm at a Krypton gas jet, followed by a Sapphire crystal at Brewster's angle for the fundamental to allow outcoupling of the harmonics. A single harmonic is selected using a time-preserving monochromator to maintain the short pulses, and is sent to an ultra high vacuum chamber with sample preparation and diagnostic tools as well as an electron energy spectrometer. This allows us to study the electronic dynamics of semiconductor surfaces and their interfaces with adsorbed molecules which enable various charge transfer effects. Supported by AFOSR.

  16. Nonadiabatic Dynamics May Be Probed through Electronic Coherence in Time-Resolved Photoelectron Spectroscopy.

    Science.gov (United States)

    Bennett, Kochise; Kowalewski, Markus; Mukamel, Shaul

    2016-02-01

    We present a hierarchy of Fermi golden rules (FGRs) that incorporate strongly coupled electronic/nuclear dynamics in time-resolved photoelectron spectroscopy (TRPES) signals at different levels of theory. Expansion in the joint electronic and nuclear eigenbasis yields the numerically most challenging exact FGR (eFGR). The quasistatic Fermi Golden Rule (qsFGR) neglects nuclear motion during the photoionization process but takes into account electronic coherences as well as populations initially present in the pumped matter as well as those generated internally by coupling between electronic surfaces. The standard semiclassical Fermi Golden Rule (scFGR) neglects the electronic coherences and the nuclear kinetic energy during the ionizing pulse altogether, yielding the classical Condon approximation. The coherence contributions depend on the phase-profile of the ionizing field, allowing coherent control of TRPES signals. The photoelectron spectrum from model systems is simulated using these three levels of theory. The eFGR and the qsFGR show temporal oscillations originating from the electronic or vibrational coherences generated as the nuclear wave packet traverses a conical intersection. These oscillations, which are missed by the scFGR, directly reveal the time-evolving splitting between electronic states of the neutral molecule in the curve-crossing regime. PMID:26691822

  17. X-ray photoelectron spectroscopy investigations of zinc-magnesium alloy coated steel

    Energy Technology Data Exchange (ETDEWEB)

    Chen Sheng, E-mail: chen_sheng@baosteel.com [Research Institute of Baoshan Iron and Steel Co. Ltd., 655 Fujin Road, Baoshan District, Shanghai 201900 (China); Yan Fei; Xue Fei; Yang Lihong; Liu Junliang [Research Institute of Baoshan Iron and Steel Co. Ltd., 655 Fujin Road, Baoshan District, Shanghai 201900 (China)

    2010-11-01

    The coating layer composition depth profiles and element chemical states of zinc-magnesium alloy coated steel were investigated by X-ray photoelectron spectroscopy depth profiling. Through the analysis of photoelectron signals and Auger signals of different elements on different depth planes of the coating layer, it can be found that the surface of the coating layer contains MgCO{sub 3}, MgO, Mg(OH){sub 2}, metallic Mg, metallic Zn and some complex zinc compounds. Under the surface, there is a Zn{sub 2}Mg alloy layer with the thickness of about 300 nm accompanied with MgO and Mg(OH){sub 2} in the layer. There is a transitional layer with the thickness of about 200 nm between the Zn{sub 2}Mg alloy layer and the pure Zn layer, whose components consist of zinc-magnesium alloy without fixed stoichiometry, a little MgO and a little Mg(OH){sub 2}.

  18. 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.

  19. 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.

  20. Microsolvation of sodium acetate in water: Anion photoelectron spectroscopy and ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wen-Jing; Hou, Gao-Lei; Wang, Peng; Xu, Hong-Guang; Feng, Gang; Xu, Xi-Ling; Zheng, Wei-Jun, E-mail: zhengwj@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-08-07

    To understand the microsolvation of sodium acetate (CH{sub 3}COONa, NaOAc) in water, we studied NaOAc(H{sub 2}O){sub n}{sup −} (n = 0–3) clusters by photoelectron spectroscopy. We also investigated the structures of NaOAc(H{sub 2}O){sub n}{sup −} (n = 0–5) anions and NaOAc(H{sub 2}O){sub n} (n = 0–7) neutrals by quantum chemistry calculations. By comparing the theoretical results with the photoelectron experiment, the most probable structures of NaOAc(H{sub 2}O){sub n}{sup −/0} (n = 0–3) were determined. The study also shows that, with increasing n, the solvent-separated ion pair (SSIP) structures of NaOAc(H{sub 2}O){sub n}{sup −} anions become nearly energetically degenerate with the contact ion pair (CIP) structures at n = 5, while the SSIP structures of the neutral NaOAc(H{sub 2}O){sub n} clusters appear at n = 6 and become dominant at n = 7.

  1. Attosecond ionization dynamics

    International Nuclear Information System (INIS)

    Complete test of publication follows. In the interaction between light and matter, the central energy and bandwidth of the radiation, in relation to the energy structure of the studied atoms or molecules, are important parameters. Extreme ultraviolet attosecond pulses, produced through high-order harmonic generation, have during the last years been increasingly used for such studies, particularly in combination with intense infrared (IR) fields, for time-resolved studies of strong field processes. Attosecond experiments have so far utilized pulses with high central energies, in excess of the ionization, potentials of the studied species. When these pulses interact with matter they induce single-photon ionization, creating electron wave packets with a significant initial energy. In the present work, we have generated attosecond pulse trains in xenon, with individual pulse durations of 370 as. Their central energy is 23 eV, which is above the ionization potential of argon (15.8 eV) and neon (21.6 eV), but below that of helium (24.6 eV). We let these pulses interact with the target gas in the presence of a strong IR laser pulse, and measure the on yield as a function of the phase of the IR field at the time of arrival of the pulse. For helium, where the central energy of the pulses is below the ionization threshold, we find a significant enhancement of the ion yield when the IR field is present. In addition, the ion yield exhibits a sub-cycle modulation as a function of the IR phase. The origin of these effects can be understood through the measured photoelectron momentum distributions, and is confirmed by theoretical calculations based on the integration of the time-dependent Schroedinger equation.

  2. In situ x-ray photoelectron spectroscopy for electrochemical reactions in ordinary solvents

    International Nuclear Information System (INIS)

    In situ electrochemical X-ray photoelectron spectroscopy (XPS) apparatus, which allows XPS at solid/liquid interfaces under potential control, was constructed utilizing a microcell with an ultra-thin Si membrane, which separates vacuum and a solution. Hard X-rays from a synchrotron source penetrate into the Si membrane surface exposed to the solution. Electrons emitted at the Si/solution interface can pass through the membrane and be analyzed by an analyzer placed in vacuum. Its operation was demonstrated for potential-induced Si oxide growth in water. Effect of potential and time on the thickness of Si and Si oxide layers was quantitatively determined at sub-nanometer resolution

  3. Analysis of brown coal fly-ash using X-ray photoelectron spectroscopy

    Science.gov (United States)

    Ersez, T.; Liesegang, J.

    1991-08-01

    The surface chemical composition of brown coal ash particles formed during combustion has been determined using the surface-sensitive technique of X-ray photoelectron spectroscopy (XPS). Samples taken from furnace heat exchanger tube surfaces were in both powder and aggregate form. Other samples were obtained directly using 1 cm 2 steel coupons on a sample holder designed for insertion into flue gases in an experimental furnace. This allowed comparison of the XPS analyses between the fly-ash samples so acquired. After initial XPS characterization, samples were subjected to rare-gas ion (Ar +) sputtering for depth profiling purposes. The XPS technique was thus used to detect any sputter-induced composition changes or to observe any difference between the surface and bulk compositions of the ash. It was also observed that certain steels used for heat exchanger piping may well be pre-disposed to aluminosilicate fouling due to their intrinsic Al content.

  4. 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.

  5. Research and industrial application of x-ray photoelectron spectroscopy (XPS) in Malaysia

    International Nuclear Information System (INIS)

    As a developing country, Malaysia is fully committed to research and development especially for industrial development. One of priority fields is advanced materials and surface analysis of such materials is an important aspect in research. Among the tools for surface science analysis is x-ray photoelectron spectroscopy (XPS) which can be considered new to this country. The industrial sector is also keen to solve their problems and developing their products using XPS. The microelectronic and electrical industries are interested in solving problems related to metal-metal joining , gold silica peeling, surface corrosion and surface coating. The glove industry uses XPS to solve problems due to staining and color fading of their products. Research conducted in universities and research institutes that mainly deal with catalysis, membranes for fuel cells, sensors, batteries, corrosion phenomena and interface interaction in coating finds XPS a useful technique for surface studies. Specific examples from various sectors will be presented in this paper. (Author)

  6. Prediction of protein interaction behaviour with PEG-grafted matrices using X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Damodaran, Vinod Babu; Fee, Conan J. [Biomolecular Interaction Centre, Department of Chemical and Process Engineering, University of Canterbury, Christchurch 8140 (New Zealand); Popat, Ketul C., E-mail: Ketul.Popat@colostate.edu [Biomaterials and Surface Micro/Nano-Engineering Laboratory, Department of Mechanical Engineering, School of Biomedical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, CO 80523 (United States)

    2010-06-01

    Due to the considerable scientific and commercial interest in poly(ethylene glycol) (PEG) grafted solid surfaces for biomedical applications, it is important to characterize the properties and behaviour of these modified surfaces. In this study, we applied a unique method to predict the magnitude of interactive forces exerted between a globular protein and PEG-grafted matrices. Carboxyl functionalized solid matrices were covalently grafted with PEG-amine derivatives at varying PEG surface concentrations and layer thicknesses by controlling the grafting reaction parameters. X-ray photoelectron spectroscopy was used to characterize these PEG-grafted matrices using the standard overlay model. A detailed and systematic correlation between PEG layer thickness and the distance between the grafted PEG chains resulted in valuable information regarding protein interactions with these PEG-grafted matrices. Finally, this predicted interaction behaviour was validated with fluorescent images obtained from fluorescein isothiocyanate-labelled Cytochrome c-conjugated solid matrices using confocal laser scanning microscopy.

  7. Prediction of protein interaction behaviour with PEG-grafted matrices using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Due to the considerable scientific and commercial interest in poly(ethylene glycol) (PEG) grafted solid surfaces for biomedical applications, it is important to characterize the properties and behaviour of these modified surfaces. In this study, we applied a unique method to predict the magnitude of interactive forces exerted between a globular protein and PEG-grafted matrices. Carboxyl functionalized solid matrices were covalently grafted with PEG-amine derivatives at varying PEG surface concentrations and layer thicknesses by controlling the grafting reaction parameters. X-ray photoelectron spectroscopy was used to characterize these PEG-grafted matrices using the standard overlay model. A detailed and systematic correlation between PEG layer thickness and the distance between the grafted PEG chains resulted in valuable information regarding protein interactions with these PEG-grafted matrices. Finally, this predicted interaction behaviour was validated with fluorescent images obtained from fluorescein isothiocyanate-labelled Cytochrome c-conjugated solid matrices using confocal laser scanning microscopy.

  8. Structural analysis of carbon materials by X-ray photoelectron spectroscopy using computational chemistry

    International Nuclear Information System (INIS)

    X-ray photoelectron spectroscopy (XPS) has been frequently utilized to analyze the structures of carbon materials. However, few types of defects such as functional groups have been identified and reported, and some of these assignments are controversial. For example, the structures of oxygen-containing functional groups of carbon materials such as graphite oxide and graphene oxide are still under debate. Reported assignments for the C1s spectra of nitrogen-containing functional groups in carbon materials are few and there has been little discussion of such spectra. One effective method to clarify the structures of carbon materials in detail is simulation of XPS spectra using computational chemistry. This work explains the current problems for the XPS analysis of the C1s spectra of carbon materials and suggests the peak positions of various oxygen- and nitrogen-containing functional groups in addition to their full width at half maximum. (author)

  9. Aqueous solution/metal interfaces investigated in operando by photoelectron spectroscopy.

    Science.gov (United States)

    Karslıoğlu, O; Nemšák, S; Zegkinoglou, I; Shavorskiy, A; Hartl, M; Salmassi, F; Gullikson, E M; Ng, M L; Rameshan, Ch; Rude, B; Bianculli, D; Cordones, A A; Axnanda, S; Crumlin, E J; Ross, P N; Schneider, C M; Hussain, Z; Liu, Z; Fadley, C S; Bluhm, H

    2015-01-01

    We describe a new in operando approach for the investigation of heterogeneous processes at solid/liquid interfaces with elemental and chemical specificity which combines the preparation of thin liquid films using the meniscus method with standing wave ambient pressure X-ray photoelectron spectroscopy [Nemšák et al., Nat. Commun., 5, 5441 (2014)]. This technique provides information about the chemical composition across liquid/solid interfaces with sub-nanometer depth resolution and under realistic conditions of solution composition and concentration, pH, as well as electrical bias. In this article, we discuss the basics of the technique and present the first results of measurements on KOH/Ni interfaces. PMID:25912462

  10. X-ray photoelectron spectroscopy study of catalyzed aluminum carbide formation at aluminum-carbon interfaces

    Science.gov (United States)

    Rabenberg, L.; Maruyama, Benji

    1990-01-01

    Aluminum carbide may form at aluminum-graphite interfaces during the high-temperature processing of graphite fiber-reinforced aluminum metal matrix composites. The chemical interactions leading to the formation of the aluminum carbide in the solid state involve the breaking of the carbon-carbon bonds within the graphite, the transport of the carbon atoms across the interface, and the reaction with the aluminum to form Al4C3. The aluminum carbide formation process has been followed using X-ray photoelectron spectroscopy of model, thin-film, reaction couples. The overall reaction is shown to be catalyzed by the presence of water vapor. Water at the interface increases reaction kinetics by apparently weakening the bonds between the surface carbon atoms and their substrate. This result is in general agreement with what is known to occur during the oxidation of graphite in air.

  11. Angularly resolved X-ray photoelectron spectroscopy investigation of PTFE after prolonged space exposure

    Science.gov (United States)

    Dalins, I.; Karimi, M.

    1992-01-01

    Monochromatized angularly resolved X-ray photoelectron spectroscopy (ARXPS) was used to study PTFE (Teflon) that had been exposed to an earth orbital environment for approximately six years. The primary interest of the research is on a very reactive component of this environment (atomic oxygen) which, because of the typical orbital velocities of a spacecraft, impinge on exposed surfaces with 5 eV energy. This presentation deals with the method of analysis, the findings as they pertain to a rather complex carbon, oxygen, and fluorine XPS peak analysis, and the character of the valence bands. An improved bias referencing method, based on ARXPS, is also demonstrated for evaluating specimen charging effects. It was found that the polymer molecule tends to resist the atomic oxygen attack by reorienting itself, so that the most electronegative CF3 groups are facing the incoming hyperthermal oxygen atoms. The implications of these findings to ground-based laboratory studies are discussed.

  12. Lyophilized histidine investigated using X-ray photoelectron spectroscopy and cryogenics: Deprotonation in vacuum

    International Nuclear Information System (INIS)

    Lyophilized histidine samples were investigated using X-ray photoelectron spectroscopy (XPS). Lyophilized samples were prepared from aqueous solutions at a pH in the range between ∼1.5 and ∼10, and with no further addition of electrolyte. The use of cryogenics allowed the determination of protonated to unprotonated molar ratios of sites in L-histidine, which correlates well with the dissociation constants of the residual amino acid sites. When cryogenics was not used deprotonation of the lyophilized samples occurred, where the degree and the total concentration of deprotonated sites correlates well with the formation constants and the decrease in Cl concentration, respectively. This later relation clearly indicates a correlation between deprotonation and the desorption of HCl from lyophilized samples

  13. Hard x-ray photoelectron spectroscopy using an environmental cell with silicon nitride membrane windows

    International Nuclear Information System (INIS)

    We applied hard x-ray photoelectron spectroscopy (HAXPES) to a sample under ambient pressure conditions using an environmental cell with an approximately 24 nm-thick SiNx membrane window. As a model chemical substance, europium (II) iodide (EuI2) sealed in the cell with argon gas was investigated with HAXPES to identify the chemical species present inside the cell. The optical and morphological properties of the sample within the cell were measured with optical and fluorescent microscopy, scanning electron microscopy, cathodoluminescence, and energy dispersive x-ray spectrometry. We confirmed the effectiveness of the gas barrier properties of the cell with the SiNx window and demonstrated its applicability to various other optical and electron measurements as well as HAXPES

  14. Electronic structure of quasicrystals deduced from Auger and x-ray photoelectron spectroscopies

    International Nuclear Information System (INIS)

    Specific features in the electronic structure of Al-transition metal quasicrystals are analysed by a combination of Auger and x-ray photoelectron spectroscopies. We first demonstrate that different degrees of asymmetry in the transition metals' 2p core-level lineshape observed across different types of surface structure correspond to variations in the density of states at the Fermi level, DOS(EF). Using this effect, we explore the controversial issue of whether the quasicrystalline, decagonal AlNiCo system is electronically stabilized. We find strong evidence for the presence of a reduced DOS(EF) in this system, as expected for electronically stabilized compounds, and as observed in the quasicrystalline, icosahedral AlPdMn and AlCuFe alloys. Finally, qualitative information on the nature of the electronic states in quasiperiodic structures extracted from the core-valence-valence Auger lines are presented and discussed. (author)

  15. 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).

  16. Detection of ultrashort VUV radiation pulses using photoelectron spectroscopy at DELTA

    International Nuclear Information System (INIS)

    At the 1.5-GeV electron storage ring DELTA operated by the TU-Dortmund University, coherent VUV radiation is generated in a short-pulse facility based on the Coherent Harmonic Generation (CHG) scheme. In this scheme, a femtosecond laser pulse is used to induce a periodic modulation of the electron energy in an undulator. The energy modulation is converted to a density modulation in a dispersive section. The resulting electron microbunches radiate coherently at higher harmonics of the laser wavelength in a second undulator. The VUV beamline operated by the Forschungszentrum Juelich will be employed for pump-probe experiments. It comprises a plane-grating monochromator and a photoelectron spectrometer optimized for angle-resolved photoemission spectroscopy. While a dedicated setup was initially used during commissioning of the short-pulse facility, the CHG-generated pulses can now be characterized directly in the VUV beamline.

  17. Oxygen Electroreduction Activity and X-Ray Photoelectron Spectroscopy of Platinum and Early Transition Metal Alloys

    DEFF Research Database (Denmark)

    Stephens, Ifan; Bech, Lone; Chorkendorff, Ib;

    2012-01-01

    The oxygen reduction reaction (ORR) was studied experimentally on sputter-cleaned, polycrystalline electrodes of Pt3Y, Pt5Y, Pt2Y, Pt3Sc, Pt3Hf, Pt3Zr and Pt under conditions relevant for low-temperature fuel cells. The surfaces were characterised insitu by means of electrochemical methods and...... exsitu under ultrahigh vacuum conditions. The ORR activity was established in an electrochemical cell containing 0.1M HClO4 by use of a rotating ring disk electrode assembly. The surface composition was characterised before and after the electrochemical measurements by using angle-resolved X......-ray photoelectron spectroscopy. The ORR activity of the electrodes increased in the following order: Pt2Y≈Pt3Zr≈Pt≈...

  18. 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...

  19. X-ray photoelectron spectroscopy analysis of organic materials etched by charged water droplet impact

    International Nuclear Information System (INIS)

    Electrospray droplet impact (EDI) has been developed for matrix-free secondary ion mass spectrometry for surface analysis. When a target is etched by EDI, the physical etching on the target is suppressed to minimal, i.e., the occurrence of shallow surface etching. A novel approach to shallow surface etching of polystyrene (PS) by EDI was investigated. The charged water droplets were irradiated to a bulk and a spin coated PS. After irradiation, these samples were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. It was found that XPS spectra for PS were independent on the irradiation time by EDI. This indicates that EDI is a unique technique for the surface etching of the organic materials without leaving any damage on the etched surface.

  20. 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.

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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).

  3. 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.

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

    International Nuclear Information System (INIS)

    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 O3-. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO2, 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 NNO2 molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO2 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 (C2- - C11-), and van der Waals clusters (X-(CO2)n, X = I, Br, Cl; n ≤ 13 and I- (N2O)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-(CO2)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

  5. 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}.

  6. Decoherence in attosecond photoionization.

    Science.gov (United States)

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

    2011-02-01

    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. PMID:21405393

  7. Electronic structure of germanium selenide investigated using ultra-violet photo-electron spectroscopy

    International Nuclear Information System (INIS)

    The valence band electronic structure of GeSe single crystals has been investigated using angle resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy. The experimentally observed bands from ARPES, match qualitatively with our LDA-based band structure calculations along the Γ–Z, Γ–Y and Γ–T symmetry directions. The valence band maximum occurs nearly midway along the Γ–Z direction, at a binding energy of −0.5 eV, substantiating the indirect band gap of GeSe. Non-dispersive features associated with surface states and indirect transitions have been observed. The difference in hybridization of Se and Ge 4p orbitals leads to the variation of dispersion along the three symmetry directions. The predominance of the Se 4pz orbitals, evidenced from theoretical calculations, may be the cause for highly dispersive bands along the Γ–T direction. Detailed electronic structure analysis reveals the significance of the cation–anion 4p orbitals hybridization in the valence band dispersion of IV–VI semiconductors. This is the first comprehensive report of the electronic structure of a GeSe single crystal using ARPES in conjugation with theoretical band structure analysis. (paper)

  8. Electronic structure of germanium selenide investigated using ultra-violet photo-electron spectroscopy

    Science.gov (United States)

    Mishra, P.; Lohani, H.; Kundu, A. K.; Patel, R.; Solanki, G. K.; Menon, Krishnakumar S. R.; Sekhar, B. R.

    2015-07-01

    The valence band electronic structure of GeSe single crystals has been investigated using angle resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy. The experimentally observed bands from ARPES, match qualitatively with our LDA-based band structure calculations along the Γ-Z, Γ-Y and Γ-T symmetry directions. The valence band maximum occurs nearly midway along the Γ-Z direction, at a binding energy of -0.5 eV, substantiating the indirect band gap of GeSe. Non-dispersive features associated with surface states and indirect transitions have been observed. The difference in hybridization of Se and Ge 4p orbitals leads to the variation of dispersion along the three symmetry directions. The predominance of the Se 4pz orbitals, evidenced from theoretical calculations, may be the cause for highly dispersive bands along the Γ-T direction. Detailed electronic structure analysis reveals the significance of the cation-anion 4p orbitals hybridization in the valence band dispersion of IV-VI semiconductors. This is the first comprehensive report of the electronic structure of a GeSe single crystal using ARPES in conjugation with theoretical band structure analysis.

  9. Investigations into the electronic structure of the high-Tc superconductors by means of photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The electronic structure of various polycrystalline samples including the new YBaCuO- and BiCaSrCuO- high Tc superconductors (HTSC) and related systems is investigated by photoelectron spectroscopy. Additional characterization is performed by conductivity measurements. In particular, the binding energy of the Cu-2p3/2- and the O-1s-levels of various HTSC is determined. For the first time the controversial 531 eV oxygen line was shown to be an intrinsic electronic structure effect. Sintered CuO-samples are obtained for the first time. The electronic structure of the sintered CuO turns out to be drastically different with respect to pressed CuO powder. For the first time a crossover resonance from a O-1s- into a Cu-3d-level was observed with synchrotron radiation. This is additional evidence for the strong hybridization between the Cu-3d and the O-2p states. Photoemission spectroscopy shows that the holes in the HTSC's are located at the oxygen p-band. Fe and Al overlayers on the HTSC-samples induce a drastic change in the electronic properties of the interface: apparently oxygen is removed from the HTSC to the overlayer. (orig./BHO)

  10. Challenges for lithium species identification in complementary Auger and X-ray photoelectron spectroscopy

    Science.gov (United States)

    Hoffmann, M.; Zier, M.; Oswald, S.; Eckert, J.

    2015-08-01

    The combination of high spatial resolution and near-surface chemical information makes Auger electron spectroscopy (AES) a powerful tool for comprehensive surface analysis. The recent interest in lithium metal as an active material in lithium sulphur or lithium air batteries increases the demand for a thorough knowledge of the reactions happening at the electrode interface. Applying AES to the complex surfaces of batteries, however, requires a detailed understanding of the interactions occurring with the highly reactive materials during investigation, especially when using metallic lithium with its passivation layers formed even under glove box atmosphere. The article is focused on the influence of electron beam damage and residual gas under ultra-high vacuum conditions on the observations made. Immediate irradiation effects are shown to highly depend on electron dose leading to misinterpretation the surface composition and a non-sufficient stability of the sample. The results are further supported by coupled X-ray photoelectron spectroscopy (XPS) measurements that help to understand the beam induced phenomena. An improved output of the spectroscopic measurement could be achieved employing AES mappings. This allows an improved insight into the local distribution of different lithium compounds in the material surface and can also be applied to other battery active materials.

  11. Fessibility Study on Nitrogen in Explosives using X-ray Photoelectron Spectroscopy: Chemical Fertilizer

    International Nuclear Information System (INIS)

    It was known that an explosive is defined as a material which contains a large amount of energy stored in chemical bonds. The energetic stability of gaseous products, and hence, their generation come from the strong bond formation of carbon (mono/di)oxide and (di)nitrogen. Consequently, most commercial explosives are contained -NO2, -ONO2 and/or -NHNO2 groups which when detonated release gases like the aforementioned ones, e.g., nitroglycerin, TNT, HMX, PETN, nitrocellulose, etc. It was revealed that the elemental compositions, especially N was found in most of the explosive and fertilizer. Chemical fertilizers that used as explosive stimulants were analyzed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscope coupled with energy-dispersive X-ray fluorescence spectroscopy (SEM-EDS). XPS spectra showed relatively high amount of nitrogen (N) in the various samples, especially sample #6 and #7. In addition, the elemental analysis revealed the presence of trace elements. Explosives and fertilizers have differences in specific compositions. It can be concluded that these methods seem to be used as a fingerprint examination to identify various kinds of explosives and fertilizers.

  12. X-ray photoelectron spectroscopy of rice husk surface modified with maleated polypropylene and silane

    International Nuclear Information System (INIS)

    Rice husks were subjected to dry-grinding and steam-explosion to reduce their sizes. Subsequently, the surface of rice husk particles was modified using two different coupling agents, maleated polypropylene (MAPP) and γ-aminopropyltriethoxysilane (γ-APS, A-1100) to induce chemical reactions between the husk surface and the coupling agents used. The modified surface properties of rice husk were examined using X-ray photoelectron spectroscopy and FT-IR spectroscopy. Dry grinding, a simple method of fracturing husk, provided particulate segments, while steam explosion separated husk into fibrous components. When treated with MAPP, the O/C ratio of the husk surface decreased for both dry ground and steam-exploded husk. The γ-APS treatment resulted in an increase in the Si/O ratio for dry ground husk surface while this ratio decreased for steam-exploded husk particles. These results indicated that both coupling agents might be linked to the husk surface through chemical reactions. FT-IR results also supported the occurrence of ester and ether bonds after treatment of husks with MAPP and γ-APS. The present work suggested that the method of preparing rice husk particles had a great impact on their surface properties, and would therefore affect the interfacial adhesion in rice husk-thermoplastic composites

  13. Electronic structure and thermal decomposition of 5-methyltetrazole studied by UV photoelectron spectroscopy and theoretical calculations

    International Nuclear Information System (INIS)

    Graphical abstract: UV photoelectron spectrum of the gas-phase thermal decomposition of 5-methyltetrazole (5MTZ), obtained at 195 °C, mechanism and potential energy diagram underlying the thermal dissociation of 5MTZ. Highlights: ► Gas-phase 5-methyltetrazole exists mainly as the 2H-tautomer. ► Thermal decomposition of 5MTZ gives N2, CH3CN and HCN, at 250 °C. ► HCN is formed from secondary reactions. - Abstract: The electronic properties and thermal decomposition of 5-methyltetrazole (5MTZ) are investigated using UV photoelectron spectroscopy (UVPES) and theoretical calculations. Simulated spectra of both 1H- and 2H-5MTZ, based on electron propagator methods, are produced in order to study the relative tautomer population. The thermal decomposition results are rationalized in terms of G2(MP2) results. 5MTZ yields a HOMO ionization energy of 10.82 ± 0.04 eV and the gas-phase 5MTZ assumes predominantly the 2H-form. Its gas-phase thermal decomposition starts at ca. 195 °C and leads to the formation of N2,CH3CN and HCN. N2 is formed from two competing routes, involving 150.2 and 126.2 kJ/mol energy barriers, from 2H- and 1H-5MTZ, respectively. CH3CN is formed also from two competing pathways, requiring activation energies of 218.3 (2H-5MTZ) and 198.6 kJ/mol (1H-5MTZ). Conclusions are also drawn in order to explain the formation of HCN from secondary reactions in the thermal decomposition process.

  14. Practical issues of retrieving isolated attosecond pulses

    International Nuclear Information System (INIS)

    The attosecond streaking technique is used for the characterization of isolated extreme ultraviolet (XUV) attosecond pulses. This type of measurement suffers from low photoelectron counts in the streaked spectrogram, and is thus susceptible to shot noise. For the retrieval of few- or mono-cycle attosecond pulses, high-intensity streaking laser fields are required, which cause the energy spectrum of above-threshold ionized (ATI) electrons to overlap with that of the streaked photoelectrons. It is found by using the principal component generalized projections algorithm that the XUV attosecond pulse can accurately be retrieved for simulated and experimental spectrograms with a peak value of 50 or more photoelectron counts. Also, the minimum streaking intensity is found to be more than 50 times smaller than that required by the classical streaking camera for retrieval of pulses with a spectral bandwidth supporting 90 as transform-limited pulse durations. Furthermore, spatial variation of the streaking laser intensity, collection angle of streaked electrons and time delay jitter between the XUV pulse and streaking field can degrade the quality of the streaked spectrogram. We find that even when the XUV and streaking laser focal spots are comparable in size, the streaking electrons are collected from a 4π solid angle, or the delay fluctuates by more than the attosecond pulse duration, the attosecond pulses can still be accurately retrieved. In order to explain the insusceptibility of the streaked spectrogram to these factors, the linearity of the streaked spectrogram with respect to the streaking field is derived under the saddle point approximation.

  15. Surface change in titanium between 25 and 10000C studied by Auger electron spectroscopy and x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The dissolution of native oxides on titanium were studied over the temperature range 25 to 10000C to determine their role in the pyrotechnic reaction of titanium with potassium perchlorate. From Auger electron spectroscopy (AES) data it was found that the solubility of the oxide in Ti increased sharply at 3500C. High resolution AES scans of the Ti LMM transitions as well as x-ray photoelectron spectroscopy (XPS) scans of the Ti 2p level showed that free Ti is present at the surface above 3500C. The O ls XPS data show that the surface contains hydroxyl as well as oxide groups. The hydroxide-to-oxide ratio begins to decrease below 2500C, and at 4500C the remaining oxygen is found predominantly as oxide. In addition, the XPS data show that the dissolution process proceeds through the formation of titanium suboxides. These AES and XPS results complement physical property measurements that have also been made on the Ti/KC1O4 mixture. Physical property measurements show that 1) below 3000C no reaction occurs, and 2) just above 3000C an exothermic reaction occurs, corresponding to the reaction of fresh titanium with atmospheric oxygen. The fixed temperature studies at 3000C and 3500C have shown that there is a semilogarithmic relationship between the surface oxygen level and the time at temperature

  16. 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. PMID:25415599

  17. Total photoelectron yield spectroscopy of diamond: teaching an old dog new tricks

    International Nuclear Information System (INIS)

    Full text: Total photoelectron yield spectroscopy (Yield) has been widely used in the past to determine the work function of metals, and the density of tail and gap states in amorphous semiconductors and at the Si/SiO2 interface, for example. In all cases advantage is taken of the unrivalled sensitivity of yield which covers more than eight orders of magnitude in the density of occupied states. However, like all photoelectron spectroscopies, Yield suffers from a short sampling depth that seldom exceeds a few nm and is determined by the inelastic mean free path of electrons with finite kinetic energies. The situation changes completely when a semiconductor with true negative electron affinity such as hydrogenated diamond is used where the vacuum level falls below the conduction band minimum. Now even electrons at the conduction band minimum contribute to the yield and the spectrum reflects the absorption process as well as the transport of thermalized electrons and excitons to the surface as has been discussed first by Bandis and Pate. Here, we have utilized yield spectra of hydrogenated homoepitaxial diamond layers with different thicknesses to determine the diffusion lengths of electrons and excitons in diamond which amount to 16 and 20 μm, respectively for the highest quality diamond. Furthermore, from changes in the relative contributions of exciton and electron excitations to the yield spectra we are able to extract the sign of subsurface band bending over the diffusion length in hydrogenated diamond. This is so because electrons are affected by the electric fields connected with band bending whereas excitons as neutral entities are not. By following the band bending as a function of surface treatment we are able to unravel the mechanism behind the p-type surface conductivity that is observed on hydrogenated diamond surfaces after exposure to air. The mechanism relies on a transfer of electrons from diamond to a redox couple in an aqueous surface layer that

  18. Resonance-enhanced multiphoton-ionization photoelectron spectroscopy of even-parity autoionizing Rydberg states of atomic sulphur

    Science.gov (United States)

    Woutersen, S.; Milan, J. B.; Buma, W. J.; de Lange, C. A.

    1997-05-01

    Several previously unobserved Rydberg states of the sulphur atom above the lowest ionization threshold are identified and assigned using (2+1) resonance-enhanced multiphoton-ionization photoelectron spectroscopy. All states were accessed by two-photon transitions from either the 3P ground or the 1D excited state, prepared by in situ photodissociation of H2S. The observed states derive from the (2Do)5p and (2Po)4p configurations. For the (2Do)5p 3F and (2Po)4p 3D triplets, extensive photoelectron spectroscopic studies enable a detailed comparison of the autoionization and photoionization rates of these states.

  19. Scanning tunneling microscopy, orbital-mediated tunneling spectroscopy, and ultraviolet photoelectron spectroscopy of metal(II) tetraphenylporphyrins deposited from vapor.

    Science.gov (United States)

    Scudiero, L; Barlow, D E; Mazur, U; Hipps, K W

    2001-05-01

    Thin films of vapor-deposited Ni(II) and Co(II) complexes of tetraphenylporphyrin (NiTPP and CoTPP) were studied supported on gold and embedded in Al-Al(2)O(3)-MTPP-Pb tunnel diodes, where M = Ni or Co. Thin films deposited onto polycrystalline gold were analyzed by ultraviolet photoelectron spectroscopy (UPS) using He I radiation. Scanning tunneling microscopy (STM) and orbital-mediated tunneling spectroscopy (STM-OMTS) were performed on submonolayer films of CoTPP and NiTPP supported on Au(111). Inelastic electron tunneling spectroscopy (IETS) and OMTS were measured in conventional tunnel diode structures. The highest occupied pi molecular orbital of the porphyrin ring was seen in both STM-OMTS and UPS at about 6.4 eV below the vacuum level. The lowest unoccupied pi molecular orbital of the porphyrin ring was observed by STM-OMTS and by IETS-OMTS to be located near 3.4 eV below the vacuum level. The OMTS spectra of CoTPP had a band near 5.2 eV (below the vacuum level) that was attributed to transient oxidation of the central Co(II) ion. That is, it is due to electron OMT via the half-filled d(z)(2) orbital present in Co(II) of CoTPP. The NiTPP OMTS spectra show no such band, consistent with the known difficulty of oxidation of the Ni(II) ion. The STM-based OMTS allowed these two porphyrin complexes to be easily distinguished. The present work is the first report of the observation of STM-OMTS, tunnel junction OMTS, and UPS of the same compounds. Scanning tunneling microscope-based orbital-mediated tunneling provides more information than UPS or tunnel junction-based OMTS and does so with molecular-scale resolution. PMID:11457159

  20. 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...

  1. Magnetron Plasma Sputtered Nanocomposite Thin Films: Structural Surface Studies by In Vacuo Photoelectron Spectroscopy

    International Nuclear Information System (INIS)

    The experimental system that enables thin film deposition by chemical vapor deposition combined with magnetron sputtering and sample surface characterization by photoelectron spectroscopy (PES), without breaking the vacuum between the deposition and the characterization stage, is described. The particular goal of this work was study of the surface arrangement of embedded metallic nanoclusters of 1B group (Au, Ag, and Cu) in amorphous hydrogenated carbon (a-C:H). From the range of applied material characterization tools, we present here the results of several PES-based experiments used to reveal cluster properties at the surface: as-deposited sample PES measurements, off-normal take-off angle XPS, and in situ in-depth XPS profiling by Ar+ ion etching. Clear distinction in all PES results of the samples deposited on the grounded substrates from those deposited on -150 V dc biased ones is obtained, revealing that keeping the substrate grounded during deposition results in topmost metallic clusters covered with a very thin layer of a-C:H, while applying negative bias voltage to the substrate results in partially bald clusters on the surface

  2. Study of the oxidation of gold-tin preforms using x-ray photoelectron spectroscopy

    Science.gov (United States)

    Taylor, J. Ashley; Merchant, Sailesh M.; Perry, D. L.

    1995-11-01

    This study uses x-ray photoelectron spectroscopy (XPS) to investigate the nature of the oxide formed on clean Au-Sn binary alloys (ζ and δ phases) and on preforms with the eutectic composition (29 at % Sn) at low O2 pressures (oxide layer. The oxidation of the Au-Sn alloys is basically similar to the oxidation of metallic Sn. The Auger parameter indicates that with low-pressure oxidation a layered oxide structure is formed consisting of SnO and a slightly tin-rich oxide at the interface. Probably a thin skin of Sn(IV) oxide exists on the outer surface of the low-pressure oxide. High-temperature and low-pressure promotes the growth of SnO. As the pressure is increased the Sn(IV) oxide grows more noticeably and with high-pressure oxidation the Sn(IV) oxide grows thicker than the Sn(II) oxide at the interface. The Sn(II) oxide at the interface appears similar to the Sn(II) oxide structure formed at low pressure. The Auger parameter indicates that the Sn(IV) oxide possesses a structure different than that of Cassiterite.

  3. 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.

  4. X-ray photoelectron spectroscopy of the uranium/oxygen system. Part XI

    International Nuclear Information System (INIS)

    As part of a wider program to investigate the low temperature oxidation behaviour of Commercial Advanced Gas-cooled Reactor UO2 fuel pellets in the event of gas ingress to a fuel can during handling or storage, the behaviour of individual grains in bulk UO2 has been simulated using single crystal surfaces. To this end the oxidation of (111), (110) and (100) planar slices of crystalline UO2 together with a polycrystalline sample of current fuel product have been oxidised in 1 Torr of oxygen at 250C, 2250C and 3000C. The oxidation process was monitored using X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy to cross-correlate changes in surface chemistry, bulk composition and oxide morphology. Factors governing the oxidation behaviour of different crystalline UO2 slices are discussed and it is proposed that the observed reactivity reflects the ease with which oxygen interstitial atoms are incorporated into the new oxide forming at the U3O7/UO2 interface. (author)

  5. Characterization of plasma fluorinated zirconia for dental applications by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    This paper discusses fluorination of biomedical-grade yttria-stabilized zirconia (YSZ) by sulfur hexafluoride plasma treatment and characterization of near-surface chemistry products by X-ray photoelectron spectroscopy (XPS). Deconvolution of the Zr 3d and Y 3d XPS core level spectra revealed formation of both ZrF4 and YF3. In addition, seven-coordinate ZrO2F5 and/or ZrO3F4 phases were deconvolved, retaining similar atomic coordination as the parent oxide and believed to have formed by substitutional displacement of oxygen by fluorine. No additional components attributed to yttria oxyfluoride were deconvolved. Argon ion sputter depth profiling determined the overlayer to be ∼4.0 nm in thickness, and angle resolved XPS showed no angle dependence on component percentages likely due to fluorination extending into the grain boundaries of the polycrystalline substrates. Importantly, the conversion layer did not induce any apparent change in zirconia crystallinity by inspection of Zr-O 3d5/2,3/2 peak positions and full-width-at-half-maximum values, important for retaining its desirable mechanical properties.

  6. Lanthanum, cerium, praseodymium, and neodymium metals and their interaction with oxygen studied by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Clean films of La, Ce, Pr, and Nd, prepared by in situ evaporation have been investigated by photoelectron spectroscopy. Different light sources He I (hv = 21.2 eV), He II (hv = 40.8 eV) and Mg Kα (hv = 1253.6 eV) have been used for the electron excitation in order to characterize the metals. Measurements have been performed after exposing the clean metals to various amounts of oxygen. From the vanishing of the emission from the sd conduction band upon exposure the conclusion is drawn that an oxide layer thicker than the probing depth (20 A) is formed on all four metals and that the oxide (at room temperature) has the form: Me2O3, Me=La, Ce, Pr, Nd. The tetravalent cerium oxide is obtained when the film is heated to about 6000C during oxygen exposure. The interaction with oxygen is also characterized by recording the oxygen 1s level and some metal core levels (Me 3d, 4d and 4p). The results from the pure metals and from the metal oxides give further experimental evidence for a 4f level binding energy of 1.9 eV in γ-cerium. (Auth.)

  7. X-ray photoelectron spectroscopy studies of MgB 2 for valence state of Mg

    Science.gov (United States)

    A. Talapatra; Bandyopadhyay, S. K.; Sen, Pintu; Barat, P.; Mukherjee, S.; Mukherjee, M.

    2005-03-01

    Core level X-ray photoelectron spectroscopy (XPS) studies have been carried out on polycrystalline MgB 2 pellets over the whole binding energy range with a view to having an idea of the charge state of magnesium (Mg). We observe three distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB 2 and MgCO 3 or, divalent Mg species, respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB 2 is lower than that corresponding to Mg(2+), indicative of the fact that the charge state of Mg in MgB 2 is less than (2+). Lowering of the formal charge of Mg promotes the σ → π electron transfer in boron (B) giving rise to holes on the top of the σ-band which are involved in coupling with B E 2g phonons for superconductivity. Through this charge transfer, Mg plays a positive role in hole superconductivity. B 1s spectra consist of three peaks corresponding to MgB 2, boron and B 2O 3. There is also evidence of MgO due to surface oxidation as seen from O 1s spectra.

  8. Thickness determination of molecularly thin lubricant films by angle-dependent X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    An angle-dependent X-ray photoelectron spectroscopy (XPS) method used to measure the thickness of molecularly thin lubricants was developed. The method was built based on an island model of patched overlayer on a flat substrate by using the photoemission signal solely from the lubricant film. Typical molecularly thin Zdol films on the CHx overcoat of unused commercial magnetic disks were measured to verify the metrology. The lubricant thickness determined by the metrology was equal to the recent result by thermostatic high vacuum atomic force microscopy. The measured deduction in the thickness of the molecularly thin lubricant films, successively irradiated by the monochromatic source operated at 14 kV/250 W, was as low as 1 A during the first irradiation hour. XPS spectra showed that no hydrocarbons, water or oxygen were adsorbed over the Zdol outer surfaces in the tested XPS conditions. The inelastic mean free path (IMFP) of C 1s in Zdol or in CHx was found to be independent of take off angle (TOA) when TOA o. The IMFP of C 1s in Zdol was ∼63.5 A and the lubricant island thickness was ∼35 A

  9. Covalently Bound Tetracoordinated Organoborons are Superhalogens: A Combined Negative Ion Photoelectron Spectroscopy and Theoretical Study

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jian; Yang, Ping; Sun, Zhenrong; Wang, Xue B.

    2014-09-18

    Molecular species with electron affinities (EAs) larger than that of the chlorine atom (3.6131 eV) are superhalogens. The corresponding negative ions, namely, superhalogen anions, are intrinsically very stable with high electron binding energies (EBEs), and widely exist as building blocks of bulk materials and ionic liquids. The most common superhalogen anions proposed and confirmed to date are either ionic salts or compact inorganic species. Herein we report a new class of superhalogen species, a series of tetracoordinated organoboron anions [BL4]– (L = phenyl (1), 4-fluorophenyl (2), 1-imidazolyl (3), L4 = H(pyrazolyl)3 (4)) with bulky organic ligands covalently bound to the central B atom. Negative ion photoelectron spectroscopy (NIPES) reveals all of these anions possessing EBEs higher than that of Cl- with the adiabatic / vertical detachment energy (ADE / VDE) of 4.44/4.8 (1), 4.78/5.2 (2), 5.08/5.4 (3), and 4.59/4.9 eV (4), respectively. First-principles calculations confirmed high EBEs of [BL4]– and predicted that these anions are thermodynamically stable against fragmentation. The unraveled superhalogen nature of these species provides a molecular basis to explain the wide-range applications of tetraphenylborate (TPB) (1) and trispyrazolylborate (Tp) (4) in many areas spanning from industrial waste treatment to soft material synthesis and organometallic chemistry

  10. Characterization of amino acid adlayers on InAs surfaces using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Removal of surface oxide layers and the prevention of their reformation is an essential step in the use of III-V semiconductor technologies. Highlighted here are data exploring the use of amino acid (AA) self-assembled monolayers (SAMs) to block the pre-growth of oxides on indium arsenide surfaces. Three different AAs were used: lysine, aspartic acid, and cysteine. The adlayers were characterized by atomic force microscopy (AFM), Raman, and angle resolved X-ray photoelectron spectroscopy (ARXPS). AFM data suggest that the AA functional groups affect the packing and orientation of the molecules on the surfaces, reinforced by contact angle data. Raman data provide proof that the type of functional group alters the intensity of the unscreened LO phonon, resulting in an electrostatic stabilization, in the case of lysine, which lends to the case of electrostatic interactions blocking oxide formation. ARXPS demonstrated that the degree of oxide blocking is dependent upon the type of functional group and further verifies inferences made from the Raman spectra. The degree of monolayer formation is also determined from this data. It is concluded that AA's can be useful means for blocking oxide growth on InAs (1 0 0) surfaces, which also provides insights into how protein and peptide side chains might interact with such surfaces.

  11. High-resolution photoelectron spectroscopy analysis of sulfidation of brass at the rubber/brass interface

    International Nuclear Information System (INIS)

    Highlights: ► Chemical composition at the rubber/brass interface is investigated. ► The 2-min vulcanization reaction is enough to convert the interface composition. ► Five S-containing species are identified at the interface. ► Strong rubber–brass adhesion is related to the Cu2S/CuS ratio. ► Degradation of adhesion proceeds along with desulfidation of the interface. - Abstract: High resolution photoelectron spectroscopy is utilized to investigate the chemical composition at the rubber/brass interface to elucidate the origin of strong adhesion as well as the degradation between rubber and brass. Special attention has been given to copper sulfides formed at the interface during the vulcanization reaction at 170 °C. At least five sulfur-containing species are identified in the adhesive interlayer including crystalline CuS and amorphous CuxS (x ≃ 2). These copper sulfide species are not uniformly distributed within the layer, but there exits the concentration gradation; the concentration of CuxS is high in the region on the rubber side and is diminished in the deeper region, while vice versa for that of CuS. Degradation of the interface adhesive strength by prolonged vulcanization arises from the decrease in the CuxS/CuS ratio accompanying desulfurization of the adhesive layer.

  12. Investigation of buried metal-organic interface with photoelectron spectroscopy (PES)

    Energy Technology Data Exchange (ETDEWEB)

    Vrdoljak, Pavo; Schoell, Achim; Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik II, 97074 Wuerzburg (Germany); Umbach, Eberhard [Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)

    2008-07-01

    Metal-organic interfaces are of crucial importance for electronic devices since they influence the layer morphology, the electronic structure at contacts, and the charge carrier transport. Various investigations have addressed this issue from the viewpoint of surface science, applying model systems with thin organic films on flat (single crystalline or amorphous) metal substrates. The contacts in electronic devices, however, can be very different. This is mainly due to the morphological roughness of the interface in case of a metal top contact deposited on an organic layer and the possible influence on the electronic structure. In case of real contacts also interdiffusion has to be taken into account. However, surface sensitive techniques such as photoelectron spectroscopy (PES) and atomic force microscopy (AFM) can not immediately access the buried interface. To tackle this problem we have applied and optimised a lift-off technique which allows the removal of the metal top-contact in the UHV and analyse the interface between the contact and the organic film. We present first PES and AFM results of Au contacts deposited on PTCDA layers.

  13. High resolution photoelectron spectroscopy at the SnPc/Ag(111) interface

    Energy Technology Data Exchange (ETDEWEB)

    Scheuermann, C.; Haeming, M.; Kroeger, I.; Stadler, C.; Kumpf, C.; Schoell, A.; Reinert, F.; Umbach, E. [Universitaet Wuerzburg, Experimentelle Physik II, 97074 Wuerzburg (Germany)

    2008-07-01

    Phthalocyanines are interesting for applications in organic devices due to the potential of tailoring their properties by introducing different metal ligands into the heterocycle. Some derivates offer the potential of tuning the work function of metal contacts due to an intrinsic dipole moment. We present a high resolution photoelectron spectroscopy study on SnPc submonolayers on Ag(111). Based on a structural analysis, which shows the existence of different adsorption phases with different orientation of the molecular dipoles depending on temperature and coverage, the PES data indicate a significant effect on the surface work function. The valence and core spectra allow identifying a covalent interaction at the interface with the appearance of a new state at EF. Moreover, the data provide evidence for a systematic weakening of the interfacial interaction with increasing coverage. This is accompanied by a constriction of the substrate-adsorbate charge transfer, which becomes evident from an analysis of the core level line shapes. As a consequence, a comprehensive description of the electronic structure in the contact regime, of the resulting interface dipole, and of work function effects needs to account not only for structural properties such as the intrinsic molecular geometry, but also for intermolecular- and interfacial interactions which may involve significant charge transfer.

  14. Characterization of plasma fluorinated zirconia for dental applications by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wolter, S.D. [Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708 (United States); Piascik, J.R., E-mail: jpiascik@rti.org [RTI International, Center for Materials and Electronic Technologies, Research Triangle Park, NC 27709 (United States); Stoner, B.R. [Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708 (United States); RTI International, Center for Materials and Electronic Technologies, Research Triangle Park, NC 27709 (United States)

    2011-09-15

    This paper discusses fluorination of biomedical-grade yttria-stabilized zirconia (YSZ) by sulfur hexafluoride plasma treatment and characterization of near-surface chemistry products by X-ray photoelectron spectroscopy (XPS). Deconvolution of the Zr 3d and Y 3d XPS core level spectra revealed formation of both ZrF{sub 4} and YF{sub 3}. In addition, seven-coordinate ZrO{sub 2}F{sub 5} and/or ZrO{sub 3}F{sub 4} phases were deconvolved, retaining similar atomic coordination as the parent oxide and believed to have formed by substitutional displacement of oxygen by fluorine. No additional components attributed to yttria oxyfluoride were deconvolved. Argon ion sputter depth profiling determined the overlayer to be {approx}4.0 nm in thickness, and angle resolved XPS showed no angle dependence on component percentages likely due to fluorination extending into the grain boundaries of the polycrystalline substrates. Importantly, the conversion layer did not induce any apparent change in zirconia crystallinity by inspection of Zr-O 3d{sub 5/2,3/2} peak positions and full-width-at-half-maximum values, important for retaining its desirable mechanical properties.

  15. Characterization of plasma fluorinated zirconia for dental applications by X-ray photoelectron spectroscopy

    Science.gov (United States)

    Wolter, S. D.; Piascik, J. R.; Stoner, B. R.

    2011-09-01

    This paper discusses fluorination of biomedical-grade yttria-stabilized zirconia (YSZ) by sulfur hexafluoride plasma treatment and characterization of near-surface chemistry products by X-ray photoelectron spectroscopy (XPS). Deconvolution of the Zr 3d and Y 3d XPS core level spectra revealed formation of both ZrF4 and YF3. In addition, seven-coordinate ZrO2F5 and/or ZrO3F4 phases were deconvolved, retaining similar atomic coordination as the parent oxide and believed to have formed by substitutional displacement of oxygen by fluorine. No additional components attributed to yttria oxyfluoride were deconvolved. Argon ion sputter depth profiling determined the overlayer to be ∼4.0 nm in thickness, and angle resolved XPS showed no angle dependence on component percentages likely due to fluorination extending into the grain boundaries of the polycrystalline substrates. Importantly, the conversion layer did not induce any apparent change in zirconia crystallinity by inspection of Zr-O 3d5/2,3/2 peak positions and full-width-at-half-maximum values, important for retaining its desirable mechanical properties.

  16. Reactivity of lithium containing amorphous hydrogenated carbon films towards oxygen: an in situ photoelectron spectroscopy study

    International Nuclear Information System (INIS)

    Amorphous hydrogenated carbon coatings (a-C : H) containing different amounts of lithium have been prepared by a modified radio frequency-plasma assisted chemical vapour deposition (rf-PACVD) technique. They have been characterized in situ by X-ray (XPS) and ultraviolet photoelectron spectroscopy (UPS). The samples have been exposed to molecular oxygen as well as an oxygen plasma in order to obtain information about the reactivity of the coatings. The effect of the oxygen plasma on pure a-C : H is found to be a mere etching, the structure of the surface itself remaining essentially unchanged. In contrast, a transition from the carbidic carbon-lithium phase to a metal-carbonate like configuration, i.e. Li2CO3 or LiHCO3, occurs in the lithium containing samples. These differences result in a much larger oxygen uptake at the surface of the lithium containing samples as compared to the pure a-C : H. Furthermore the rate of etching by the oxygen plasma is substantially lower for the lithium containing films. ((orig.))

  17. X-ray photoelectron spectroscopy study of Pd oxidation by RF discharge in oxygen

    International Nuclear Information System (INIS)

    The low-temperature oxidation of polycrystalline palladium by RF oxygen plasma was studied via X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Detailed information about the electronic states of palladium and oxygen was obtained based on the XPS curve fitting analysis of Pd3d and Pd3p + O1s lines. The results showed that Pd oxidation by oxygen plasma was different from Pd oxidation in pure O2 at high temperature. SEM shows well-structured submicron PdO particles result from oxidation in pure O2, whereas plasma oxidation results in the predominant formation of two-dimensional PdO structures covering the initial crystallites of the Pd foil. Further oxidation to a three-dimensional PdO phase occurs under prolonged treatment with oxygen plasma. The formation of a PdOx (x > 1) species, characterized by a Eb(Pd3d5/2) = 338.0-338.2 eV value that is close to the Pd4+ oxidation state, was also observed. This PdOx species was found to have low thermal stability (T x species can be localized within the boundaries of crystallites.

  18. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    Science.gov (United States)

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-10-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry.

  19. 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.

  20. Electronic structure of the L-cysteine films on dental alloys studied by ultraviolet photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The valence electronic structures of the dental alloys, type 1, type 3, K14, and MC12 and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The electronic states of the MC12 dental alloy originate dominantly from Cu 3d states and Pd 4d states around the top of the valence bands, while the 4∼7-eV electronic structure of MC12 originates from the Ag 4d states. The peak shift and the change in shape due to alloying are observed in all the dental alloys. For the L-cysteine thin films, new peak or structure observed around 2 eV on all the dental alloys is suggested to be due to the bonding of S 3sp orbitals with the dental alloy surfaces. The Cu-S bond as well as the Au-S and Au-O bonds may cause the change in the electronic structure of the L-cysteine on type 1, type 3 and K14. For MC12, the interaction with L-cysteine may be dominantly due to the Pd-S, Cu-S, and Ag-O bonds, while the contribution of the Ag-S bond is small.

  1. A fast and flexible multichannel electron detector with parallel readout for photoelectron spectroscopy

    Science.gov (United States)

    Manning, P. P.; Clague, N. J.; Kirkman, I. W.; Quinn, F. M.; Hicks, P. J.

    1997-02-01

    To satisfy end user requirements for higher throughput and reliability in photoelectron spectroscopy, a new multichannel electron detector with discrete electronics has been designed and commissioned at Daresbury Laboratory. Count rate performance has been enhanced by the use of low resistance microchannel plates which amplify the electron pulses incident on the anode array. The low resistance microchannel plates are linear to 2.5 × 10 4 s -1 mm -2 for a bias voltage of 900 V per plate, providing more than an order of magnitude improvement in count rate performance over high resistance microchannel plates, microchannel plate outgassing in the ultra-high vacuum environment limits the scale of this improvement. A novel anode design maximizes the collection efficiency, while minimising crosstalk between channels (rail and electrodes on the anode. Each data collection channel comprises a fast current amplifier and discriminator, capable of a throughput of 2.5 × 10 7 s -1, and a 24 bit scaler. The integral non-linearity for flat-field illumination is better than 10% with no correction. The fast multichannel detection system gives a throughput enhancement of 10-20 on single-channel detection systems. It has also proved to be significantly better than previous multichannel detection systems with discrete electronics due to its high throughput, modular design and flexible structure.

  2. X-ray photoelectron spectroscopy studies of MgB2 for valence state of Mg

    International Nuclear Information System (INIS)

    Core level X-ray photoelectron spectroscopy (XPS) studies have been carried out on polycrystalline MgB2 pellets over the whole binding energy range with a view to having an idea of the charge state of magnesium (Mg). We observe three distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB2 and MgCO3 or, divalent Mg species, respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB2 is lower than that corresponding to Mg(2+), indicative of the fact that the charge state of Mg in MgB2 is less than (2+). Lowering of the formal charge of Mg promotes the σ → π electron transfer in boron (B) giving rise to holes on the top of the σ-band which are involved in coupling with B E2g phonons for superconductivity. Through this charge transfer, Mg plays a positive role in hole superconductivity. B 1s spectra consist of three peaks corresponding to MgB2, boron and B2O3. There is also evidence of MgO due to surface oxidation as seen from O 1s spectra

  3. 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.

  4. Stoichiometry Investigations of pulsed laser deposited Si/SiOx thin films studied by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    We report on X-ray photoelectron spectroscopy (XPS) studies of thin silicon, SiOx, and SiO2 film in order to investigate the chemical composition and the chemical bonding of these deposits. The films were previously fabricated by means of pulsed laser deposition using a high power Nd:Yagi laser operating at a wavelength of 1054 nm in order to ablate a silicon target in an argon and/or oxygen atmosphere. Film thickness between 80 and 130 nm were achieved. The XPS investigations show that the stoichiometry of the SiOx films can be varied between x=0 and x=2 by changing the oxygen partial pressure in the deposition chamber. While pure silicon films can be successfully deposited in a pure argon atmosphere, SiO2 deposits were achieved in pure oxygen or mixed oxygen/argon atmospheres respectively. Substoichiometric SiOx films were only deposited in atmospheres containing very low contents of oxygen, which means Ar/O2 ratios in the magnitude of 50:1. The obtained results were compared with secondary ion mass spectroscopy investigations of the same films. In addition, both techniques were used to perform depth profiles analysis of the SiOx layers in order to study the uniformity of the elemental distribution and the chemical bonding within the films. It is found that the variation of the chemical compositions is only in the range of some percent, proofing the ability to grow homogenous thin SiOx films with a defined stoichiometry by pulsed laser deposition. (Authors)

  5. Ab-initio angle and energy resolved photoelectron spectroscopy with time-dependent density-functional theory

    CERN Document Server

    De Giovannini, U; Marques, M A L; Appel, H; Gross, E K U; Rubio, A

    2012-01-01

    We present a time-dependent density-functional method able to describe the photoelectron spectrum of atoms and molecules when excited by laser pulses. This computationally feasible scheme is based on a geometrical partitioning that efficiently gives access to photoelectron spectroscopy in time-dependent density-functional calculations. By using a geometrical approach, we provide a simple description of momentum-resolved photoe- mission including multi-photon effects. The approach is validated by comparison with results in the literature and exact calculations. Furthermore, we present numerical photoelectron angular distributions for randomly oriented nitrogen molecules in a short near infrared intense laser pulse and helium-(I) angular spectra for aligned carbon monoxide and benzene.

  6. Multiphoton Double Ionization of Ar in Intense Extreme Ultraviolet Laser Fields Studied by Shot-by-Shot Photoelectron Spectroscopy

    International Nuclear Information System (INIS)

    Photoelectron spectroscopy has been performed to study the multiphoton double ionization of Ar in an intense extreme ultraviolet laser field (hν∼21 eV, ∼5 TW/cm2), by using a free electron laser (FEL). Three distinct peaks identified in the observed photoelectron spectra clearly show that the double ionization proceeds sequentially via the formation of Ar+: Ar+hν→Ar++e- and Ar++2hν→Ar2++e-. Shot-by-shot recording of the photoelectron spectra allows simultaneous monitoring of FEL spectrum and the multiphoton process for each FEL pulse, revealing that the two-photon ionization from Ar+ is significantly enhanced by intermediate resonances in Ar+.

  7. High temperature and high resolution uv photoelectron spectroscopy using supersonic molecular beams

    International Nuclear Information System (INIS)

    A high temperature molecular beam source with electron bombardment heating has been built for high resolution photoelectron spectroscopic studies of high temperature species and clusters. This source has the advantages of: producing an intense, continuous, seeded molecular beam, eliminating the interference of the heating mechanism from the photoelectron measurement. Coupling the source with our hemispherical electron energy analyzer, we can obtain very high resolution HeIα (584 angstrom) photoelectron spectra of high temperature species. Vibrationally-resolved photoelectron spectra of PbSe, As2, As4, and ZnCl2 are shown to demonstrate the performance of the new source. 25 refs., 8 figs., 1 tab

  8. 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.

  9. 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

  10. Photoelectron Spectroscopy and Theoretical Studies of Anion-pi Interactions: Binding Strength and Anion Specificity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jian; Zhou, Bin; Sun, Zhenrong; Wang, Xue B.

    2015-01-01

    illustrates that size-selective photoelectron spectroscopy combined with theoretical calculations represent a powerful technique to probe intrinsic anion–π interactions and has potential to provide quantitative guest-host molecular binding strengths and unravel fundamental insights in specific anion recognitions.

  11. Photoelectron spectroscopy and theoretical studies of anion-π interactions: binding strength and anion specificity.

    Science.gov (United States)

    Zhang, Jian; Zhou, Bin; Sun, Zhen-Rong; Wang, Xue-Bin

    2015-02-01

    Proposed in theory and then their existence confirmed, anion-π interactions have been recognized as new and important non-covalent binding forces. Despite extensive theoretical studies, numerous crystal structural identifications, and a plethora of solution phase investigations, anion-π interaction strengths that are free from complications of condensed-phase environments have not been directly measured in the gas phase. Herein we present a joint photoelectron spectroscopic and theoretical study on this subject, in which tetraoxacalix[2]arene[2]triazine 1, an electron-deficient and cavity self-tunable macrocyclic, was used as a charge-neutral molecular host to probe its interactions with a series of anions with distinctly different shapes and charge states (spherical halides Cl(-), Br(-), I(-), linear thiocyanate SCN(-), trigonal planar nitrate NO3(-), pyramidic iodate IO3(-), and tetrahedral sulfate SO4(2-)). The binding energies of the resultant gaseous 1 : 1 complexes (1·Cl(-), 1·Br(-), 1·I(-), 1·SCN(-), 1·NO3(-), 1·IO3(-) and 1·SO4(2-)) were directly measured experimentally, exhibiting substantial non-covalent interactions with pronounced anion-specific effects. The binding strengths of Cl(-), NO3(-), IO3(-) with 1 are found to be strongest among all singly charged anions, amounting to ca. 30 kcal mol(-1), but only about 40% of that between 1 and SO4(2-). Quantum chemical calculations reveal that all the anions reside in the center of the cavity of 1 with an anion-π binding motif in the complexes' optimized structures, where 1 is seen to be able to self-regulate its cavity structure to accommodate anions of different geometries and three-dimensional shapes. Electron density surface and charge distribution analyses further support anion-π binding formation. The calculated binding energies of the anions and 1 nicely reproduce the experimentally estimated electron binding energy increase. This work illustrates that size-selective photoelectron

  12. Diagrammatic approach to attosecond delays in photoionization

    CERN Document Server

    Dahlström, J M; Lindroth, E

    2012-01-01

    We study laser-assisted photoionization by attosecond pulses using a time-independent formalism based on diagrammatic many-body perturbation theory. Our aim is to provide an ab inito route to the "delays" for this above-threshold ionization process, which is essential for a quantitative understanding of attosecond metrology. We present correction curves for characterization schemes of attosecond pulses, such as "streaking", that account for the delayed atomic response in ionization from neon and argon. We also verify that photoelectron delays from many-electron atoms can be measured using similar schemes if, instead, the so-called continuum--continuum delay is subtracted. Our method is general and it can be extended also to more complex systems and additional correlation effects can be introduced systematically.

  13. Attosecond delays in molecular photoionization

    CERN Document Server

    Huppert, Martin; Baykusheva, Denitsa; von Conta, Aaron; Wörner, Hans Jakob

    2016-01-01

    We report measurements of energy-dependent attosecond photoionization delays between the two outer-most valence shells of N$_2$O and H$_2$O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N$_2$O, whereas the delays in H$_2$O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N$_2$O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to $\\sim$110 as. The unstructured continua of H$_2$O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.

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

    International Nuclear Information System (INIS)

    In this study, 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

  15. 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.

  16. Oxidation Half-Reaction of Aqueous Nucleosides and Nucleotides via Photoelectron Spectroscopy Augmented by ab Initio Calculations

    Czech Academy of Sciences Publication Activity Database

    Schroeder, C. A.; Pluhařová, Eva; Seidel, R.; Schroeder, W. P.; Faubel, M.; Slavíček, P.; Winter, B.; Jungwirth, Pavel; Bradforth, S. E.

    2015-01-01

    Roč. 137, č. 1 (2015), s. 201-209. ISSN 0002-7863 R&D Projects: GA ČR GBP208/12/G016 Grant ostatní: GA ČR(CZ) GA13-34168S Institutional support: RVO:61388963 Keywords : DNA damage * photoelectron spectroscopy * DNA charge migration Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 12.113, year: 2014 http://pubs.acs.org/doi/10.1021/ja508149e

  17. Direct observation of the energetics at a semiconductor/liquid junction by operando X-ray photoelectron spectroscopy

    OpenAIRE

    Lichterman, Michael F.; Hu, Shu; Richter, Matthias H.; Crumlin, Ethan J.; Axnanda, Stephanus; Favaro, Marco; Drisdell, Walter; Hussain, Zahid; Mayer, Thomas; Brunschwig, Bruce S.; Lewis, Nathan S.; Liu, Zhi; Lewerenz, Hans-Joachim

    2015-01-01

    Photoelectrochemical (PEC) cells based on semiconductor/liquid interfaces provide a method of converting solar energy to electricity or fuels. Currently, the understanding of semiconductor/liquid interfaces is inferred from experiments and models. Operando ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) has been used herein to directly characterize the semiconductor/liquid junction at room temperature under real-time electrochemical control. X-ray synchrotron radiation in conjuncti...

  18. 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

  19. Studies on CdTe solar cell front contact properties using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The chemical changes between transparent conducting oxide (TCO) and cadmium sulphide (CdS) layers were analyzed using X-ray photoelectron spectroscopy (XPS). Commercially available indium tin oxide (ITO) and ITO/SnO2 were used as substrates. The CdS layers were deposited in vacuum (∼ 10−2 Pa) at two different (low and high) substrate temperatures by close spaced sublimation technique. During the growth of CdS layer, the substrate temperature was increased from 25 to 250 °C for low temperature layer and from 490 to 550 °C for high temperature CdS layer due to the high crucible temperature. Similar to CdTe solar cell device process steps, the samples (TCO/CdS) were annealed in vacuum (10−2 Pa) at 520 °C and in air at 375 °C with and without CdCl2. The XPS depth profile analysis shows that annealing ITO/CdS sample in vacuum induces diffusion of indium into the CdS layer from ITO. The most of the diffused indium atoms are found on top of the CdS layer. No indium diffusion into the CdS layer was observed for the TCO with SnO2 buffer layer between ITO and CdS. However, at SnO2/CdS interface Cd atoms diffuse into the SnO2 buffer layer after CdCl2 activation. The change in chemical and electronic properties of the ITO/CdS and ITO/SnO2/CdS interfaces is discussed in detail. - Highlights: • The chemical change between different layers of CdTe solar cell is analyzed. • The annealing treatment induces diffusion of chemical elements. • SnO2 buffer layer acts as barrier for indium diffusion. • The CdCl2 annealing induces cadmium diffusion into tin oxide layer

  20. X-ray Photoelectron Spectroscopy Study of Argon-Plasma-Treated Fluoropolymers

    Science.gov (United States)

    Golub, Morton A.; Lopata, Eugene S.; Finney, Lorie S.

    1994-01-01

    Films of poly(tetrafluoroethylene) (PTFE) and of a tetrafluoroethylene-perfluoroalkyl vinyl ether (approximately 49:1) copolymer (PFA) were exposed to a radio-frequency argon plasma and then examined by X-ray photoelectron spectroscopy (XPS). The use of fluoropolymer films nearly free of surface hydrocarbon contamination as well as the use of a monochromatized X-ray source for XPS removed two factors contributing to conflicting reports on the effect of exposure time on the fluorine-to-carbon (F/C) and oxygen-to-carbon (O/C) ratios for several Ar-plasma-treated fluoropolymers. Contrary to literature indications, a common pattern was found for PTFE and PFA: a moderate decrease in F/C ratio (from 1.99 to 1.40, and from 1.97 to 1.57, respectively), together with a moderate increase in O/C ratio (from negligible to about 0.10, and from 0.012 to about O.10, respectively) at very short exposures, after which the F/C ratios remained essentially constant on prolonged exposures, while the O/C ratios for PTFE and PFA leveled off at 0.11 and 0.15, respectively. The XPS C(sub 1s), spectra for these polymers exposed to the Ar plasma for 20 min were similar and presented, besides a prominent peak at 292.0 eV (CF2,) and a minor peak at 294.0 or 294.1 eV (CF3), a composite band of four curve-resolved peaks (approximately 285-290 eV) representing various CH, CC, CO, CN, and CF functionalities.

  1. Investigation of the surface composition of electrodeposited black chromium by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Survilienė, S., E-mail: sveta@ktl.mii.lt; Češūnienė, A.; Jasulaitienė, V.; Jurevičiūtė, I.

    2015-01-01

    Highlights: • Black chromium electrodeposited from a Cr(III) bath is composed of oxide, hydroxide and metallic chromium. • Metallic phase is absent in black chromium electrodeposited from a Cr(III) + ZnO bath. • The near-surface layer is rich in hydroxides, whereas oxides of both metals predominate in the depth of the coatings. - Abstract: The paper reviews black chromium electrodeposited from a trivalent chromium bath containing ZnO as a second main component. The chemical compositions of the top layers of the black chromium coatings were studied by the X-ray photoelectron spectroscopy method. The surface of black chromium was found to be almost entirely covered with organic substances. To gain information on the state of each element in the deposit bulk, the layer-by-layer etching of the black chromium surface with argon gas was used. Analysis of XPS spectra has shown that the top layers of black chromium without zinc are composed of various Cr(III) components, organic substances and metallic Cr, whereas metallic Cr is almost absent in black chromium containing some amount of Zn(II) compounds. The ratios of metal/oxide phases were found to be 10/27 and 2/28 for black chromium without and with zinc, respectively. It has been determined that owing to the presence of ZnO in the Cr(III) bath, the percentage of metallic chromium is substantially reduced in black chromium which is quite important for good solar selective characteristics of the coating. The results confirm some of earlier observations and provide new information on the composition of the near-surface layers.

  2. Investigation of the surface composition of electrodeposited black chromium by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Highlights: • Black chromium electrodeposited from a Cr(III) bath is composed of oxide, hydroxide and metallic chromium. • Metallic phase is absent in black chromium electrodeposited from a Cr(III) + ZnO bath. • The near-surface layer is rich in hydroxides, whereas oxides of both metals predominate in the depth of the coatings. - Abstract: The paper reviews black chromium electrodeposited from a trivalent chromium bath containing ZnO as a second main component. The chemical compositions of the top layers of the black chromium coatings were studied by the X-ray photoelectron spectroscopy method. The surface of black chromium was found to be almost entirely covered with organic substances. To gain information on the state of each element in the deposit bulk, the layer-by-layer etching of the black chromium surface with argon gas was used. Analysis of XPS spectra has shown that the top layers of black chromium without zinc are composed of various Cr(III) components, organic substances and metallic Cr, whereas metallic Cr is almost absent in black chromium containing some amount of Zn(II) compounds. The ratios of metal/oxide phases were found to be 10/27 and 2/28 for black chromium without and with zinc, respectively. It has been determined that owing to the presence of ZnO in the Cr(III) bath, the percentage of metallic chromium is substantially reduced in black chromium which is quite important for good solar selective characteristics of the coating. The results confirm some of earlier observations and provide new information on the composition of the near-surface layers

  3. Improved performances of nanosilicon electrodes using the salt LiFSI: a photoelectron spectroscopy study.

    Science.gov (United States)

    Philippe, Bertrand; Dedryvère, Rémi; Gorgoi, Mihaela; Rensmo, Håkan; Gonbeau, Danielle; Edström, Kristina

    2013-07-01

    Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A nondestructive depth resolved analysis was carried out by using both soft X-rays (100-800 eV) and hard X-rays (2000-7000 eV) from two different synchrotron facilities and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery. PMID:23763546

  4. X-ray photoelectron and X-ray Auger electron spectroscopy studies of heavy ion irradiated C60 films

    International Nuclear Information System (INIS)

    The influence of 200 MeV Au ion irradiation on the surface properties of polycrystalline fullerene films has been investigated. The X-ray photoelectron and X-ray Auger electron spectroscopies are employed to study the ion-induced modification of the fullerene, near the surface region. The shift of C 1s core level and decrease in intensity of shake-up satellite were used to investigate the structural changes (like sp2 to sp3 conversion) and reduction of π electrons, respectively, under heavy ion irradiation. Further, X-ray Auger electron spectroscopy was employed to investigate hybridization conversion qualitatively as a function of ion fluence

  5. Introductory Lecture. Probing wavepacket dynamics with femtosecond energy- and angle-resolved photoelectron spectroscopy

    OpenAIRE

    Takatsuka, Kazuo; Arasaki, Yasuki; Wang, Kwanghsi; McKoy, Vincent

    2000-01-01

    Several recent studies have demonstrated how well-suited femtosecond time-resolved photoelectron spectra are for mapping wavepacket dynamics in molecular systems. Theoretical studies of femtosecond photoelectron spectra which incorporate a robust description of the underlying photoionization dynamics should enhance the utility of such spectra as a probe of wavepackets and of the evolution of electronic structure. This should be particularly true in regions of avoided crossings where the photo...

  6. ASCITOVG - FORTRAN PROGRAM FOR X-RAY PHOTOELECTRON SPECTROSCOPY DATA REFORMATTING

    Science.gov (United States)

    Able, P. B.

    1994-01-01

    a four-block information section ahead of the actual data. The header information is needed because data files from a number of different experimental techniques, as well as multi-region and depth profile data, can be analyzed with the EDP software. This information includes general information about the data file, names of spectral regions, descriptive comments, information about the experimental technique, and information about the experimental conditions such as the type of scan, the range of the scan, the excitation source, and the analyzer mode. The files produced by ASCITOVG are in the form of a single-spectral-region, binding-energy-scan, x-ray photoelectron spectroscopy spectrum. Comments are included in the source code, which should allow easy expansion of the program to certain other types of data files. This FORTRAN program was implemented on an IBM PC XT with the MS-DOS 3.1 operating system. It has a memory requirement of 53 KB and was developed in 1989.

  7. 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.

  8. Dual analyzer system for surface analysis dedicated for angle-resolved photoelectron spectroscopy at liquid surfaces and interfaces

    Science.gov (United States)

    Niedermaier, Inga; Kolbeck, Claudia; Steinrück, Hans-Peter; Maier, Florian

    2016-04-01

    The investigation of liquid surfaces and interfaces with the powerful toolbox of ultra-high vacuum (UHV)-based surface science techniques generally has to overcome the issue of liquid evaporation within the vacuum system. In the last decade, however, new classes of liquids with negligible vapor pressure at room temperature—in particular, ionic liquids (ILs)—have emerged for surface science studies. It has been demonstrated that particularly angle-resolved X-ray Photoelectron Spectroscopy (ARXPS) allows for investigating phenomena that occur at gas-liquid and liquid-solid interfaces on the molecular level. The results are not only relevant for IL systems but also for liquids in general. In all of these previous ARXPS studies, the sample holder had to be tilted in order to change the polar detection angle of emitted photoelectrons, which restricted the liquid systems to very thin viscous IL films coating a flat solid support. We now report on the concept and realization of a new and unique laboratory "Dual Analyzer System for Surface Analysis (DASSA)" which enables fast ARXPS, UV photoelectron spectroscopy, imaging XPS, and low-energy ion scattering at the horizontal surface plane of macroscopically thick non-volatile liquid samples. It comprises a UHV chamber equipped with two electron analyzers mounted for simultaneous measurements in 0° and 80° emission relative to the surface normal. The performance of DASSA on a first macroscopic liquid system will be demonstrated.

  9. Practical chemical analysis of Pt and Pd based heterogeneous catalysts with hard X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Highlights: •Hard X-ray photoelectron spectroscopy (HAXPES) enables interface analysis of catalyst. •HAXPES enables overall analysis of porous film of Pt-doped CeO2 and related catalyst. •HAXPES enables analysis of trace elements for Pd and Pt3Ni nanoparticle catalysts. -- Abstract: Interfacial properties including configuration, porosity, chemical states, and atomic diffusion greatly affect the performance of supported heterogeneous catalysts. Hard X-ray photoelectron spectroscopy (HAXPES) can be used to analyze the interfaces of heterogeneous catalysts because of its large information depth of more than 20 nm. We use HAXPES to examine Pt-doped CeO2 and related thin film catalysts evaporated on Si, carbon, and carbon nanotube substrates, because Pt-doped CeO2 has great potential as a noble metal-based heterogeneous catalyst for fuel cells. The HAXPES measurements clarify that the dopant material, substrate material, and surface pretreatment of substrate are important parameters that affect the interfacial properties of Pt-doped CeO2 and related thin film catalysts. Another advantage of HAXPES measurement of heterogeneous catalysts is that it can be used for chemical analysis of trace elements by detecting photoelectrons from deep core levels, which have large photoionization cross-sections in the hard X-ray region. We use HAXPES for chemical analysis of trace elements in Pd nanoparticle catalysts immobilized on sulfur-terminated substrates and Pt3Ni nanoparticle catalysts enveloped by dendrimer molecules

  10. X-Ray photoelectron spectroscopy (XPS) studies of copper-sodium tellurite glasses

    International Nuclear Information System (INIS)

    Sodium tellurite glasses containing CuO with the nominal composition [(Na2O)0.3(TeO2)0.7-x (CuO)x], where x=0.00, 0.05, 0.15, and 0.20, have been prepared and investigated by X-ray photoelectron spectroscopy (XPS). The binding energies of Te 3p, Te 3d, O 1s, and Cu 2p core levels in these glasses have been measured and compared to the corresponding binding energies in TeO2 and CuO powders. The Te 3p and Te 3d core levels for the glasses were essentially unchanged from those of TeO2 powder and have little dependence upon the CuO content. Although the O 1s peak showed a small asymmetry on the higher energy side of the peak in the glasses, it was primarily the result of hydroxide contamination on the glass surface rather than the appearance of non-bridging oxygen atoms arising from a structural change in the TeO4. For glasses with x=0.05 and 0.15, the Cu 2p peaks were shifted by more than 1 eV towards lower binding energies in comparison to their values in CuO powder, which suggests the presence of Cu+ ions in these glasses. The appearance of satellite peaks in the Cu 2p spectra, however, provided definitive evidence for the presence of Cu2+ ions in these glass samples as well. The broadened Cu 2p3/2 peaks were correspondingly decomposed into two distinct peaks separated by approximately 1.25 eV, with the lower energy peak being associated with Cu+ and the higher one with Cu2+. The relative Cu2+ content estimated from the spectral analysis was found to vary from 15% for the x=0.05 glass sample to over 70% for the x=0.20 sample

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

    International Nuclear Information System (INIS)

    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 106 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 Nd3+ is substituted for Na+. 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

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

    International Nuclear Information System (INIS)

    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

  13. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-10-08

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and near ambient-pressure of oxygen using X-ray photoelectron spectroscopy (APXPS). Oxygen reduction and evolution reactions take place on the surface of the mixed electronic and Li+ ionic conductor, LixV2O5, which eliminate parasitic reactions between oxygen reduction/evolution reaction intermediates and aprotic electrolytes used in Li-O2 batteries reported to date. Under UHV, reversible lithium intercalation and de-intercalation from LixV2O5 was noted, where the changes in the vanadium valence state revealed from XPS in this study were comparable to that reported previously from Li/LixV2O5 thin film batteries. In presence of oxygen near ambient pressure, the LixV2O5 surface was covered gradually by the reaction product of oxygen reduction, namely lithium peroxide (Li2O2) (approximately 1-2 unit cells) upon discharge. Interestingly, the LixV2O5 surface became re-exposed upon charging, and the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of Li-O2 cells (~1000 mV) with aprotic electrolytes, which can be attributed to subnanometer-thick Li2O2 with surfaces free of contaminants such as carbonate species. Our study provides first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry.

  14. 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.

  15. 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

  16. Effect of laser spectral bandwidth on coherent control of resonance-enhanced multiphoton-ionization photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The high-resolution (2 + 1) resonance-enhanced multiphoton-ionization photoelectron spectroscopy (REMPI-PS) can be obtained by measuring the photoelectron intensity at a given kinetic energy and scanning the single π phase step position. In this paper, we further demonstrate that the high-resolution (2 + 1) REMPI-PS cannot be achieved at any measured position of the kinetic energy by this measurement method, which is affected by the laser spectral bandwidth. We propose a double π phase step modulation to eliminate the effect of the laser spectral bandwidth, and show the advantage of the double π phase step modulation on achieving the high-resolution (2 + 1) REMPI-PS by considering the contributions involving on- and near-resonant three-photon excitation pathways

  17. Direct Imaging of Transient Fano Resonances in N2 Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy

    Science.gov (United States)

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J. J.; Kornilov, Oleg

    2016-04-01

    Autoionizing Rydberg states of molecular N2 are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14 ±1 fs , while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance.

  18. Direct Imaging of Transient Fano Resonances in N_{2} Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy.

    Science.gov (United States)

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J J; Kornilov, Oleg

    2016-04-22

    Autoionizing Rydberg states of molecular N_{2} are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14±1  fs, while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance. PMID:27152799

  19. 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

  20. 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.

  1. Shape resonances in the angle-resolved photoelectron spectroscopy of the Si 2p shell of SiCl4

    International Nuclear Information System (INIS)

    The partial cross sections and angular distribution parameters, β, have been determined for the 2p subshell in SiCl4. These data were obtained with angle-resolved photoelectron spectroscopy and the use of synchrotron radiation for a range of photon energies from 114 to 150 eV. The same quantities were calculated by use of a multiple scattering Xα method, and the agreement between experiment and theory is very good. In particular, the behavior of shape resonances was well predicted. The nature of shape resonances as a function of molecular orbitals in SiCl4 is discussed, and the importance of such intercomparison is emphasized

  2. X-Ray Photoelectron Spectroscopy study for far UV-Excimer laser (λ = 193nm) surface modifications of polyethylene terephtalate

    International Nuclear Information System (INIS)

    We have studied by X-Ray Photoelectron Spectroscopy (XPS), the surface of Polyethylene Terephtalate treated by pulsed far Ultra Violet (UV) radiation delivered by an Excimer laser (λ = 193nm). Treatments were carried out under different gaseous atmospheres to discriminate the mechanisms leading to the modifications of the polymer surface. In particular, a pronounced deoxidation due to the loss of CO and CO2 is observed below the ablation threshold. Furthermore, treatments under oxygen and nitrogen atmospheres reveal the opportunity of grafting new functionalities at the polymer surfaces. (author). 13 refs, 4 figs, 3 tabs

  3. 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.

  4. Electronic structure of β-Ga2O3 single crystals investigated by hard X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    By combination of hard X-ray photoelectron spectroscopy (HAXPES) and first-principles band structure calculations, the electronic states of β-Ga2O3 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-Ga2O3

  5. Resonance-enhanced multiphoton ionization photoelectron spectroscopy of even-parity autoionizing Rydberg states of atomic sulphur

    OpenAIRE

    Woutersen, S.; Milan,, M; Lange; Buma, W.J.

    1997-01-01

    Several previously unobserved Rydberg states of the sulphur atom above the lowest ionization threshold are identified and assigned using (2 + 1) resonance-enhanced multiphoton-ionization photoelectron spectroscopy. All states were accessed by two-photon transitions from either the 3P ground or the 1D excited state, prepared by in situ photodissociation of H2S. The observed states derive from the (2Do)5p and (2Po)4p configurations. For the (2Do)5p 3F and (2Po)4p 3D triplets, extensive photoele...

  6. Resonance enhanced multiphoton ionization photoelectron spectroscopy on nano- and picosecond timescales of Rydberg states of methyl iodide

    OpenAIRE

    Buma, W.J.; Dobber, M.R.; Lange

    1993-01-01

    Rydberg states of methyl iodide have been investigated using resonance enhanced multiphoton ionization in combination with photoelectron spectroscopy with nanosecond and picosecond laser pulses. The study of the ns (6n10) Rydberg states in two-, three-, and four-photon excitations has resulted in an unambiguous identification of state [1] in the 7s and 8s Rydberg states. As a consequence, it is concluded that the transition to 6s[1] in two- and three-photon excitations is anomalously weak. Th...

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

    International Nuclear Information System (INIS)

    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 Ti3+ is the first oxidation state observed, followed by Ti4+, whereas Ti2+ is practically absent during the whole process. Our results compare well with the existing literature on Ti films produced using other techniques.

  8. 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.

  9. Communication: Vibrationally resolved photoelectron spectroscopy of the tetracyanoquinodimethane (TCNQ) anion and accurate determination of the electron affinity of TCNQ

    International Nuclear Information System (INIS)

    Tetracyanoquinodimethane (TCNQ) is widely used as an electron acceptor to form highly conducting organic charge-transfer solids. Surprisingly, the electron affinity (EA) of TCNQ is not well known and has never been directly measured. Here, we report vibrationally resolved photoelectron spectroscopy (PES) of the TCNQ− anion produced using electrospray and cooled in a cryogenic ion trap. Photoelectron spectrum taken at 354.7 nm represents the detachment transition from the ground state of TCNQ− to that of neutral TCNQ with a short vibrational progression. The EA of TCNQ is measured accurately to be 3.383 ± 0.001 eV (27 289 ± 8 cm−1), compared to the 2.8 ± 0.1 eV value known in the literature and measured previously using collisional ionization technique. In addition, six vibrational peaks are observed in the photoelectron spectrum, yielding vibrational frequencies for three totally symmetric modes of TCNQ. Two-photon PES via a bound electronic excited state of TCNQ− at 3.100 eV yields a broad low kinetic energy peak due to fast internal conversion to vibrationally excited levels of the anion ground electronic state. The high EA measured for TCNQ underlies its ability as a good electron acceptor

  10. 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.

  11. Oxidation half-reaction of aqueous nucleosides and nucleotides via photoelectron spectroscopy augmented by ab initio calculations.

    Science.gov (United States)

    Schroeder, Christi A; Pluhařová, Eva; Seidel, Robert; Schroeder, William P; Faubel, Manfred; Slavíček, Petr; Winter, Bernd; Jungwirth, Pavel; Bradforth, Stephen E

    2015-01-14

    Oxidative damage to DNA and hole transport between nucleobases in oxidized DNA are important processes in lesion formation for which surprisingly poor thermodynamic data exist, the relative ease of oxidizing the four nucleobases being one such example. Theoretical simulations of radiation damage and charge transport in DNA depend on accurate values for vertical ionization energies (VIEs), reorganization energies, and standard reduction potentials. Liquid-jet photoelectron spectroscopy can be used to directly study the oxidation half-reaction. The VIEs of nucleic acid building blocks are measured in their native buffered aqueous environment. The experimental investigation of purine and pyrimidine nucleotides, nucleosides, pentose sugars, and inorganic phosphate demonstrates that photoelectron spectra of nucleotides arise as a spectral sum over their individual chemical components; that is, the electronic interactions between each component are effectively screened from one another by water. Electronic structure theory affords the assignment of the lowest energy photoelectron band in all investigated nucleosides and nucleotides to a single ionizing transition centered solely on the nucleobase. Thus, combining the measured VIEs with theoretically determined reorganization energies allows for the spectroscopic determination of the one-electron redox potentials that have been difficult to establish via electrochemistry. PMID:25551179

  12. 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.

  13. Photoelectron and UV absorption spectroscopy for determination of electronic configurations of negative molecular ions: Chlorophenols

    Energy Technology Data Exchange (ETDEWEB)

    Tseplin, E.E. [Institute of Molecular and Crystal Physics, Ufa Research Centre, Russian Academy of Sciences, October Prospect 151, Ufa 450075 (Russian Federation)], E-mail: tzeplin@mail.ru; Tseplina, S.N.; Tuimedov, G.M.; Khvostenko, O.G. [Institute of Molecular and Crystal Physics, Ufa Research Centre, Russian Academy of Sciences, October Prospect 151, Ufa 450075 (Russian Federation)

    2009-04-15

    The photoelectron and UV absorption spectra of p-, m-, and o-chlorophenols in the gas phase have been obtained. On the basis of DFT B3LYP/6-311++G(d, p) calculations, the photoelectron bands have been assigned to occupied molecular orbitals. From the TDDFT B3LYP/6-311++G(d, p) calculation results, the UV absorption bands have been assigned to excited singlet states of the molecules under investigation. For each excited state a dominant transition was found. It has been shown that the energies of these singlet transitions correlate with the energy differences between the ground-state molecular orbitals participating in them. Using the UV spectra interpretation, the electronic states of molecular anions detected earlier for the same compounds by means of the resonant electron capture mass-spectrometry have been determined.

  14. 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.

  15. Attosecond Time-Resolved Autoionization of Argon

    International Nuclear Information System (INIS)

    Autoionization of argon atoms was studied experimentally by transient absorption spectroscopy with isolated attosecond pulses. The peak position, intensity, linewidth, and shape of the 3s3p6np 1P Fano resonance series (26.6-29.2 eV) were modified by intense few-cycle near infrared laser pulses, while the delay between the attosecond pulse and the laser pulse was changed by a few femtoseconds. Numerical simulations revealed that the experimentally observed splitting of the 3s3p64p 1P line is caused by the coupling between two short-lived highly excited states in the strong laser field.

  16. Attosecond intramolecular electron dynamics

    Directory of Open Access Journals (Sweden)

    Jaroń-Becker A.

    2013-03-01

    Full Text Available We present results of numerical simulations indicating a complex laser driven electron dynamics inside simple molecular systems on the attosecond time scale. This attosecond electron dynamics influences the instant of ionization of the molecule and the final electron momentum distributions.

  17. 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.

  18. Coverage dependent reaction of yttrium on silicon and the oxidation of yttrium silicide investigated by x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The reaction of yttrium (Y) on (001) silicon (Si) with low temperature annealing is investigated for different coverages of Y using in situ x-ray photoelectron spectroscopy. The authors have also performed oxidation studies for Y on Si in the formation of yttrium silicate by a two-step process. This consists of an ex situ oxidation of Y-Si film, which is formed from low temperature annealing in vacuum. These films were then probed with depth profiling x-ray photoelectron spectroscopy. They report on three general reaction phases of Y on Si that are coverage dependent. Different coverages show differences in Si mixing and selective ultrahigh vacuum oxidation. They also report on the self-limiting formation of yttrium silicate at room temperature and low annealing temperature, which is insensitive to the annealing ambient. They also highlight the importance of oxygen partial pressure in both initial silicate formation and the extent of oxidation at different annealing temperatures. Finally, the authors also show that a high oxygen diffusion barrier prevents the oxidation of the entire Y-Si film

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

    International Nuclear Information System (INIS)

    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

  20. Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented.

  1. 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.

  2. Theoretical and Experimental Photoelectron Spectroscopy Characterization of the Ground State of Thymine Cation.

    Science.gov (United States)

    Majdi, Youssef; Hochlaf, Majdi; Pan, Yi; Lau, Kai-Chung; Poisson, Lionel; Garcia, Gustavo A; Nahon, Laurent; Al-Mogren, Muneerah Mogren; Schwell, Martin

    2015-06-11

    We report on the vibronic structure of the ground state X̃(2)A″ of the thymine cation, which has been measured using a threshold photoelectron photoion coincidence technique and vacuum ultraviolet synchrotron radiation. The threshold photoelectron spectrum, recorded over ∼0.7 eV above the ionization potential (i.e., covering the whole ground state of the cation) shows rich vibrational structure that has been assigned with the help of calculated anharmonic modes of the ground electronic cation state at the PBE0/aug-cc-pVDZ level of theory. The adiabatic ionization energy has been experimentally determined as AIE = 8.913 ± 0.005 eV, in very good agreement with previous high resolution results. The corresponding theoretical value of AIE = 8.917 eV has been calculated in this work with the explicitly correlated method/basis set (R)CCSD(T)-F12/cc-pVTZ-F12, which validates the theoretical approach and benchmarks its accuracy for future studies of medium-sized biological molecules. PMID:25539153

  3. 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.

  4. 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...

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

    International Nuclear Information System (INIS)

    We present a new theoretical approach to attosecond laser-assisted photo- and Compton ionization. Attosecond x-ray absorption and scattering are described by S-circumflex(1,2)-matrices, which are coherent superpositions of 'monochromatic' S-circumflex(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.

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

    Science.gov (United States)

    Embong, Zaidi; Johar, Saffuwan; Tajudin, Saiful Azhar Ahmad; Sahdan, Mohd Zainizan

    2015-04-01

    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 Si2+ and Al2+ cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail.

  7. 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.

  8. 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. PMID:26931704

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

    International Nuclear Information System (INIS)

    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 Si2+ and Al2+ cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail

  10. Time-, angle- and kinetic-energy-resolved photoelectron spectroscopy of highly excited states of NO

    International Nuclear Information System (INIS)

    We investigate non-adiabatic dynamics of NO molecules that are photo-excited in the vacuum ultraviolet photon energy range using time-resolved velocity map imaging. Highly excited valence and Rydberg states are populated with a tunable (147–151 nm) femtosecond laser pulse and then ionized by a time-delayed near-IR laser pulse. Three main contributions are observed in the photoelectron kinetic spectra with corresponding electron yields that show pronounced oscillations. Two oscillations are assigned to ro-vibronic coupling in the valence-Rydberg mixture of the B′2Δ(v=7) and 4dδ N2Δ(v = 0) states and the B2Π(v = 25) and 4pπ K2Π(v = 1) states, respectively. We assign a third oscillation to originate from a coupling between two Rydberg states. (paper)

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

    Science.gov (United States)

    Flori, M.; Gruzza, B.; Bideux, L.; Monier, G.; Robert-Goumet, C.; Benamara, Z.

    2009-08-01

    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 °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.

  12. 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.

  13. Lineshapes, shifts and broadenings in dynamical X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    We describe in detail a model that can be used to estimate the X-ray photoelectron spectroscopic data of surfaces when a time varying bias or a modulation of the electrical properties of the surface is applied by external stimulation, in the presence of a neutralizing electron beam. Using the model and spectra recorded under periodic sample bias modulation, certain electronic properties related to charging dynamics of the surface can be estimated. The resulting technique is a non-contact impedance measurement technique with chemical specificity. Typical behavior of spectra under a square wave bias is given. Alternative modulation schemes are investigated, including small-signal square wave modulation, sinusoidal modulation and modulation of sample resistivity under fixed bias.

  14. X-ray photoelectron spectroscopy of the uranium/oxygen system: Part 13

    International Nuclear Information System (INIS)

    The reaction between commercial H2 and uranium metal leads to the formation of UO2 due to traces of water vapour or oxygen. When extremely pure H2 is used uranium hydride may be formed but, even with 99.9999% H2, uranium dioxide forms preferentially. The present work identifies the presence of UH3 in the X-ray photoelectron spectrum of a uranium sample which has been exposed to ∼ 5 mbar H2 at ∼ 2000C for 1 hour. This spectrum indicates that the hydride possesses a high degree of covalency, since the oxidation state of uranium in UH3 appears to be ∼ 1.4. (U.K.)

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

    International Nuclear Information System (INIS)

    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.

  16. Valence photodissociation of trifluoroethyl iodide investigated by photoelectron photoion coincidence spectroscopy

    International Nuclear Information System (INIS)

    Highlights: •Experimental and theoretical Investigation of trifluoroethyl iodide molecule. •Photoelectron photoion coincidence spectra in the 10–22 eV range. •VUV photoionization and dissociation dynamics. -- Abstract: Dissociative photoionization of trifluoroethyl iodide (C2H2F3I) molecule has been investigated by electron-ion coincidence technique (PEPICO) and VUV synchrotron radiation. Mass spectra have been recorded for this molecule in the photon energy range of 10–22 eV. The molecular ion as well as cationic fragments have been detected and analyzed as a function of photon energy and the main dissociation pathways are proposed. We also performed ab initio calculations for the neutral molecule, its cation and the ion fragments in order to determine electronic and structural parameters

  17. Anion Photoelectron Spectroscopy of Mo-V Binary Transition Metal Suboxide Clusters

    Science.gov (United States)

    Jarrold, Caroline Chick; Mann, Jennifer E.; Waller, Sarah E.; Rothgeb, David W.

    2010-06-01

    Vibrationally-resolved photoelectron spectra of molybdenum vanadium oxo cluster anions with 2 to 5 oxygen atoms and measured using 2.33 eV, 3.49 eV and 4.66 eV photon energies generally exhibit broad and overlapping electronic states. The adiabatic electron affinities for the series are 1.68(3) eV, 1.73(3) eV, 2.89(1) eV, and 3.4(1) eV for two through five oxygen atoms, respectively. Vibrational structure observed in the spectra can be reconciled with the lowest energy structural isomers of the anions determined in DFT calculations: The lowest energy isomers have low symmetry, with the Mo center in a higher oxidation state than the V center, and high spin states are favored.

  18. Formation of potentially protective oxide-free phosphate films on titanium characterized by valence band x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    This paper reports the results of a continuing study focused on preparing novel surface chemistries on metal surfaces. In this paper we report how it is possible to prepare oxide-free titanium metal surfaces protected by a film consisting of phosphate. The surface is prepared by electrochemical treatment in an anaerobic cell which allows electrochemistry to be conducted on samples located in a vacuum system attached to an x-ray photoelectron spectrometer. When a clean metal surface is subjected to electrochemical treatment in aqueous orthophosphoric acid an oxide-free phosphate film can be formed on the metal which is stable on subsequent air exposure. Compositional variations were found with potential and other factors. Identical electrochemical treatment of as-received titanium metal yielded samples that had a surface consisting largely of oxide. The chemical composition of these surface films was studied by core level and valence band x-ray photoelectron spectroscopy. Valence band photoemission interpreted by band structure calculations was found to be especially effective in understanding subtle differences in surface chemistry, enabling the clear identification of phosphate (being able to distinguish between orthophosphate and metaphosphate films) and its distinction from surface oxide. Valance band spectra calculated from band structure calculations for TiO, Ti2O3, TiO2, TiC, TiPO4, and TiP2O7 are reported

  19. Electronic structure at the perylene-tetracarboxylic acid dianhydride/Ag(111) interface studied with two-photon photoelectron spectroscopy.

    Science.gov (United States)

    Sachs, Sönke; Schwalb, Christian H; Marks, Manuel; Schöll, Achim; Reinert, Friedrich; Umbach, Eberhard; Höfer, Ulrich

    2009-10-14

    The electronic structure of the prototype metal/organic contact 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on a Ag(111)-surface has been investigated using time- and angle-resolved two-photon photoelectron spectroscopy (2PPE). Our analysis addresses particularly the nature of the interface state (IS) emerging at the interface due to the substrate-adsorbate interaction [C. H. Schwalb, S. Sachs, M. Marks et al., Phys. Rev. Lett. 101, 146801 (2008)]. Its free-electron-like dispersion and a possible backfolding at the surface Brillouin zone boundaries are discussed. Time-resolved pump-probe experiments reveal the inelastic electron lifetime along the dispersion parabola and show its decrease for increasing parallel momentum. The temperature dependence of the peak linewidth indicates a coupling of the IS to molecular vibrations. Moreover, additional aspects are addressed, such as the determination of the electron attenuation length of photoelectrons for low kinetic energy originating from the IS and the work function change of the sample upon PTCDA adsorption with very high energy resolution. PMID:19831458

  20. Sub-100ps single photoelectron time resolution of a strip silicon photomultiplier for time-resolved optical spectroscopy

    Science.gov (United States)

    Wang, Shenyuan; Liu, Rongdan; Liang, Kun; Yang, Ru; Han, Dejun

    2015-10-01

    SiPM with epitaxial quenching resistors developed at NDL (Novel Device Laboratory, Beijing) could alleviate the conflict between large dynamic range and high photon detection efficiency (PDE). It can be used as low light level detector in various applications with excellent single photoelectron time resolution (SPTR) and photon counting capacity. SPTR is mainly determined by the intrinsic structure parameters of the SiPM. However, it is also limited to measurement setup, electronics readout and the ultra-small signal of single photoelectron level. In this work, we designed and fabricated a 1 mm × 1 mm strip SiPM array for possible applications in time-resolved optical spectroscopy. The SiPM array consists of sixteen 50 μm × 1 mm strip SiPM elements. Each element contains five hundred 6.5 μm × 6.5 μm micro avalanche photodiode (APD) cells with 10μm pitch. The strip SiPM demonstrated SPTR of 68 ps (FWHM), peak PDE of 17% around 450 nm and high photon number resolving and photon counting capability.

  1. An X-ray photoelectron spectroscopy study of the thermal nitridation of SiO2/Si

    Science.gov (United States)

    Vasquez, R. P.; Madhukar, A.; Grunthaner, F. J.; Naiman, M. L.

    1986-01-01

    The dependence of the nitrogen distribution in thermally nitrided SiO2 films on the nitridation time and temperature has been studied by means of X-ray photoelectron spectroscopy (XPS). The photoelectron peak intensities were measured by fitting Voigt profiles to the XPS spectra and were used to calculate the film composition as a function of film depth, applying an analytical method described in detail. The times of appearance of the maxima in interfacial nitrogen concentration are shown for 800, 1000, and 1150 C, and the data are related to a kinetic model of Vasquez and Madhukar (1985), which considers the effect of interfacial strain on the nitridation kinetics. In addition, the intensity of a fluorine marker (from the HF used in the etching step) was found to correlate with the nitrogen concentration. It is postulated that the F bonds preferentially to defects. This hypothesis and the measured F intensities are consistent with the proposed strain-dependent energy of defect formation.

  2. Resonance-enhanced multiphoton-ionization photoelectron spectroscopy of even-parity Rydberg states of atomic sulfur

    Science.gov (United States)

    Woutersen, S.; Milan, J. B.; Buma, W. J.; de Lange, C. A.

    1996-12-01

    A (2+1) resonance-enhanced multiphoton-ionization photoelectron spectroscopy study of the sulfur atom was performed in the one-photon energy region between 260 and 240 nm. Some 20 previously unobserved even-parity Rydberg states of the sulfur atom are reported, which were accessed by two-photon transitions from the 3P ground state of the atom, prepared by in situ photodissociation of H2S. The (4So)np 3P series could be followed up to n=25. This series is perturbed around n=7 by an interloping Rydberg state converging to the first excited ionic limit 2Do. A two-channel quantum defect theory analysis was performed in order to estimate the composition of the wave functions of the perturbed series members, which is compared with the ionic state branching ratios obtained from photoelectron spectra. This analysis, moreover, enabled the determination of the ionization energy of the lowest ionic state 4So with an improved accuracy as compared to the previously reported value.

  3. Direct Experimental Observation of the Low Ionization Potentials of Guanine in Free Oligonucleotides by Using Photoelectron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xin; Wang, Xue B.; Vorpagel, Erich R.; Wang, Lai S.

    2004-12-21

    Photodetachment photoelectron spectroscopy is used to probe the electronic structure of mono-, di-, and trinucleotide anions in the gas phase. A weak and well defined threshold band was observed in the photoelectron spectrum of 2' -deoxyguanosine 5' -mono-phosphate at a much lower ionization energy than the other three mononucleotides. Density function theory calculations revealed that this unique spectral feature is caused by electron-detachment from a ? orbital of the guanine base on 2? ?deoxyguanosine 5? ?monophosphate, whereas the lowest ionization channel for the other three mononucleotides takes place from the phosphate group. This low-energy feature was shown to be a ?fingerprint? in all the spectra of dinucleotides and trinucleotides that contain the guanine base. The current experiment provides direct spectroscopic evidence that the guanine base is the site with the lowest ionization potential in oligonucleotides and DNA and is consistent with the fact that guanine is most susceptible to oxidation to give the guanine cation in DNA damage.

  4. Forward scattering in hard X-ray photoelectron spectroscopy: Structural investigation of buried Mn–Ga films

    International Nuclear Information System (INIS)

    X-ray photoelectron diffraction (XPD) in combination with hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the structure of buried layers in thin multilayer films. A detailed layer-by-layer investigation was performed using the element-specific, local-probe character of XPD. In the present work, angular-resolved HAXPES at a photon energy of 7.94 keV photon energy was used to investigate a Cr/Mn62Ga38/Mg/MgO multilayer system. Differences in the angular distributions of electrons emitted from Mn and Ga atoms revealed that the structure of Mn62Ga38 changes from L10 towards D022 for increasing annealing temperatures. A c/a ratio of 1.81 ± 0.06 was determined for the buried Mn62Ga38 layer in a D022 structure from the XPD experiment. The improvement of the structural order of the Mn62Ga38 layer is accompanied by an improvement of the structure of the overlying MgO layer

  5. Towards attosecond XUV pulses

    International Nuclear Information System (INIS)

    We are constructing a system for attosecond pulse generation via high-order harmonics generation in noble gases. To obtain a single attosecond pulse rather than a pulse train, we employ the regime of a few-cycle-pulse-driven harmonics generation. To achieve it, we are developing an external pulse compressor down to 7 - 10 fs using a gas-filled hollow fiber followed by chirped mirrors. We also proposed the method of high-energy attosecond pulse generation using high-order harmonics generated during the interaction of a relativistic-irradiance laser pulse with a thin foil. (author)

  6. 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

  7. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    International Nuclear Information System (INIS)

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ∼1.7 eV, values that are lower than the RCB of the uncomplexed PtCl62− dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl62− ⋅ thymine and PtCl62− ⋅ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)42− ⋅ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl62− ⋅ nucleobase spectra obtained in this work, as for the previously studied Pt(CN)42− ⋅ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to allow autodetachment

  8. Photoelectron Spectroscopy of Hexachloroplatinate-Nucleobase Complexes: Nucleobase Excited State Decay Observed via Delayed Electron Emission

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ananya; Matthews, Edward M.; Hou, Gao-Lei; Wang, Xue B.; Dessent, Caroline

    2015-11-14

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ~1.7 eV, values that are lower than the RCB of the uncomplexed PtCl6 2- dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl6 2-∙thymine and PtCl6 2-∙adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)4 2-∙nucleobase complexes [Sen et al, J. Phys. Chem. B, 119, 11626, 2015]. The observation of delayed electron emission bands in the PtCl6 2-∙nucleobase spectra obtained in this work, as for the previously studied Pt(CN)4 2-∙nucleobase complexes, is attributed to onephoton excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a timescale long enough to allow autodetachment.

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

    International Nuclear Information System (INIS)

    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.

  10. 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.

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

    Science.gov (United States)

    Imam, H.; Ahmed, Doaa; Eldakrouri, Ashraf

    2013-06-01

    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.

  12. The effect of Sr and Bi on the Si(100) surface oxidation - Auger electron spectroscopy, low energy electron diffraction, and X-ray photoelectron spectroscopy study

    Science.gov (United States)

    Fan, W. C.; Mesarwi, A.; Ignatiev, A.

    1990-01-01

    The effect of Sr and Bi on the oxidation of the Si(100) surface has been studied by Auger electron spectroscopy, low electron diffraction, and X-ray photoelectron spectroscopy. A dramatic enhancement, by a factor of 10, of the Si oxidation has been observed for Si(100) with a Sr overlayer. The SR-enhanced Si oxidation has been studied as a function of O2 exposure and Sr coverage. In contrast to the oxidation promotion of Sr on Si, it has been also observed that a Bi overlayer on Si(100) reduced Si oxidation significantly. Sr adsorption on the Si(100) with a Bi overlayer enhances Si oxidation only at Sr coverage of greater than 0.3 ML.

  13. Electronic structure of MoSe2, MoS2, and WSe2. I. Band-structure calculations and photoelectron spectroscopy

    OpenAIRE

    Coehoorn, R.; Haas, C.; Dijkstra, J.; Flipse, C.J.F.; de Groot, R. A.; Wold, A.

    1987-01-01

    The band structures of the semiconducting layered compounds MoSe2, MoS2, and WSe2 have been calculated self-consistently with the augmented-spherical-wave method. Angle-resolved photoelectron spectroscopy of MoSe2 using He I, He II, and Ne I radiation, and photon-energy-dependent normal-emission photoelectron spectroscopy using synchrotron radiation, show that the calculational results give a good description of the valence-band structure. At about 1 eV below the top of the valence band a dis...

  14. X-ray photoelectron spectroscopy of pulsed laser deposited Pb(Zr,Ti)O{sub 3-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Dragoi, Cristina; Gheorghe, Nicoleta G.; Lungu, George A.; Trupina, Lucian; Ibanescu, Andra G.; Teodorescu, Cristian M. [National Institute of Materials Physics, Magurele-Ilfov (Romania)

    2012-06-15

    High quality pulsed laser deposited lead zirconate titanate (PZT) films are obtained by pulsed laser deposition on SrRuO{sub 3}(111) single crystal layers and characterized by X-ray photoelectron spectroscopy (XPS), to determine the surface composition. It is found that a minor amount of Pb forms PbO{sub 2} at the surface and also some Pb is included into the contamination layer, in form of a Pb(CO{sub 3}){sub 2} layer of about 1 nm thickness, occupying about one quarter of the PZT surface. The stoichiometry of the outermost 4-5 nm layers yielded as PbZr{sub 0.25}Ti{sub 0.80}O{sub 2.5}, which suggest the formation of an oxygen depleted, Brownmillerite-like layer at the surface, of at least 5 nm thickness. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. 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

    its high theoretical capacity (220 mA h g-1) LiFeBO3 is a promising cathode material for lithium ion batteries. However, its application is limited because of significant degradation due to surface reactions upon exposure to moisture and air. Therefore, detailed compositional characterization of Li......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 interface...... transport processes, the presented combinatorial approach is a very valuable tool in characterizing battery electrodes and their interfaces. We apply this technique to lithium iron borate (LiFeBO3) battery electrodes at different cycling conditions to study the surface and interface layer evolution. Due to...

  16. Further insights into the photodegradation of poly(3-hexylthiophene) by means of X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Manceau, Matthieu [Clermont Universite, Universite Blaise Pascal, LPMM, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6505, LPMM, F-63177 Aubiere (France); CEA-Grenoble DRT/LITEN/DTS/LCS, INES-RDI, Laboratoire des Composants Solaires, 50 avenue du Lac Leman BP 332, 73377 Le Bourget Du Lac (France); Gaume, Julien; Rivaton, Agnes [Clermont Universite, Universite Blaise Pascal, LPMM, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6505, LPMM, F-63177 Aubiere (France); Gardette, Jean-Luc, E-mail: luc.gardette@univ-bpclermont.f [Clermont Universite, Universite Blaise Pascal, LPMM, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6505, LPMM, F-63177 Aubiere (France); Monier, Guillaume; Bideux, Luc [Clermont Universite, Universite Blaise Pascal, LASMEA, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6602, LASMEA, F-63177 Aubiere (France)

    2010-09-30

    X-ray photoelectron spectroscopy (XPS) was used to monitor the chemical changes resulting from irradiation (> 295 nm) in air of poly(3-hexylthiophene) (P3HT), polymer which is a good candidate for photovoltaic applications. The formation of carbonyl moieties and the stepwise oxidation of sulphur atoms were characterised. The oxidation and the cleavage of the hexyl side-chain was monitored. It is also shown that sulfur was first converted into sulfoxides, then into sulfones and finally into sulfinate esters. The formation of these ultimate degradation products provoked a disruption of {pi}-conjugation in P3HT, leading to diminished visible absorbance. Based on these results, a mechanism of P3HT photooxidation is proposed. Comparison of XPS data with previously reported infrared and UV-visible spectral analysis showed that the information provided by these techniques is completely consistent.

  17. Band alignment of TiO2/FTO interface determined by X-ray photoelectron spectroscopy: Effect of annealing

    Directory of Open Access Journals (Sweden)

    Haibo Fan

    2016-01-01

    Full Text Available The energy band alignment between pulsed-laser-deposited TiO2 and FTO was firstly characterized using high-resolution X-ray photoelectron spectroscopy. A valence band offset (VBO of 0.61 eV and a conduction band offset (CBO of 0.29 eV were obtained across the TiO2/FTO heterointerface. With annealing process, the VBO and CBO across the heterointerface were found to be -0.16 eV and 1.06 eV, respectively, with the alignment transforming from type-I to type-II. The difference in the band alignment is believed to be dominated by the core level down-shift of the FTO substrate, which is a result of the oxidation of Sn. Current-voltage test has verified that the band alignment has a significant effect on the current transport of the heterojunction.

  18. Structure of Se-rich As-Se glasses by high-resolution x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    To establish the validity of various proposed structural models, we have investigated the structure of the binary AsxSe100-x chalcogenide glass family (x≤40) by high-resolution x-ray photoelectron spectroscopy. From the composition dependence of the valence band, the contributions to the density of states from the 4p lone pair electrons of Se and the 4p bonding states and 4s electrons of Se and As are identified in the top part of the band. The analysis of Se 3d and As 3d core-level spectra supports the so-called chain crossing model for the atomic structure of Se-rich AsxSe100-x bulk glasses. The results also indicate small deviations (∼3-8%) from this model, especially for glass compositions with short Se chains (2540Se60 and of Se-Se-Se fragments in a glass with composition x=30 is established

  19. 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.

  20. In situ photoelectron spectroscopy study of TiCxNy films synthesized through reactive ion beam mixing

    International Nuclear Information System (INIS)

    Oxygen-free TiCxNy films have been prepared using the reactive ion beam mixing technique. A 400 A thick film of Ti was deposited on a float glass substrate and then coated with a 80 A Carbon layer. These bilayer structures were irradiated by 4 keV nitrogen ions for different nitrogen doses. In situ core level x-ray photoelectron spectroscopy (XPS) measurements were carried out to characterize these films. XPS results revealed that after nitrogen ion bombardment a sufficient amount of nitrogen was introduced in the Ti/C bilayer. On the basis of the binding energy parameters of the Ti 2p, N 1s and C 1s core levels and their shifts from the elemental position, the formation of compound TiCxNy near the surface is confirmed. The XPS result of formation of TiCxNy is supported by x-ray diffraction measurements

  1. Analysis of X-Ray Photoelectron Spectroscopy of Polymethyl Methacrylate Etched by a KrF Excimer Laser

    Institute of Scientific and Technical Information of China (English)

    ZHU Xiao-Li; LIU Shi-Bing; CHEN Tao; JIANG Yi-Jian; ZUO Tie-Chuan

    2005-01-01

    @@ The C1s and O 1s electrons in polymethyl methacrylate etched by different incident laser intensities are analysed by x-ray photoelectron spectroscopy. The results show that when the incident laser fluence increases gradually,the percentage of carbon atoms in C-C bonds decreases while the one in carbonyl group (C=O) and alkoxy group (C-O) increases, and the percentage of oxygen atoms in C=O bonds increases while the one in C-O bonds decreases. Based on the analysis of the chemical structure, the energy level transition, energy diversion, and dissociation of bonds are theoretically examined, which is consistent with the experimental results.

  2. X-ray Photoelectron Spectroscopy of the Passive Surface of Nickel-Carbon Electrocatalysts after Polarisation in Sulfuric Acid

    International Nuclear Information System (INIS)

    Thin films of nickel-carbon prepared by d.c. magnetron sputter deposition have previously been shown to exhibit passivity against corrosion as well as electrocatalytic activity towards the hydrogen oxidation reaction of the low-temperature acidic fuel cell. Pure nickel dissolves rapidly under such conditions. X-ray photoelectron spectroscopy (XPS) of Ni-C films containing between 13 and 64 at.% Ni, and polarized at +0.15 V(SHE) in 1.5 M H2SO4 at room temperature demonstrates that this passivity is not due to oxide formation, but rather to the presence of the carbon component. XPS identifies the Ni component as being in the metallic state, both before and after polarization in acid. The carbon component comprises a range of phases, with a graphitic or graphenic component being responsible for passivation

  3. Austenitic and duplex stainless steels in simulated physiological solution characterized by electrochemical and X-ray photoelectron spectroscopy studies.

    Science.gov (United States)

    Kocijan, Aleksandra; Conradi, Marjetka; Schön, Peter M

    2012-04-01

    A study of oxide layers grown on 2205 duplex stainless steel (DSS) and AISI 316L austenitic stainless steel in simulated physiological solution is presented here in order to establish the possibility of replacement of AISI 316 L with 2205 DSS in biomedical applications. The results of the potentiodynamic measurements show that the extent of the passive range significantly increased for DSS 2205 compared to AISI 316L stainless steel. Cyclic voltammetry was used to investigate electrochemical processes taking place on the steel surfaces. Oxide layers formed by electrochemical oxidation at different oxidation potentials were studied by X-ray photoelectron spectroscopy, and their compositions were analyzed as a function of depth. The main constituents on both the investigated materials were Cr- and Fe-oxides. Atomic force microscopy topography studies revealed the higher corrosion resistance of the DSS 2205 compared to the AISI 316L under the chosen experimental conditions. PMID:22331841

  4. Probing buried organic-organic and metal-organic heterointerfaces by hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Shibuta, Masahiro; Eguchi, Toyoaki; Watanabe, Yoshio; Nakajima, Atsushi [JST, ERATO, Nakajima Designer Nanocluster Assembly Project, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Son, Jin-Young; Oji, Hiroshi [Japan Synchrotron Radiation Research Institute/SPring8, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)

    2012-11-26

    We present a nondestructive characterization method for buried hetero-interfaces for organic/organic and metal/organic systems using hard x-ray photoelectron spectroscopy (HAXPES) which can probe electronic states at depths deeper than {approx}10 nm. A significant interface-derived signal showing a strong chemical interaction is observed for Au deposited onto a C{sub 60} film, while there is no such additional feature for copper phthalocyanine deposited onto a C{sub 60} film reflecting the weak interaction between the molecules in the latter case. A depth analysis with HAXPES reveals that a Au-C{sub 60} intermixed layer with a thickness of 5.1 nm is formed at the interface.

  5. Surface Oxidative Characterization of LPE HgCdTe Epilayer Studied by X-ray Photoelectron Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    李毅; 易新建; 蔡丽萍

    2000-01-01

    The surface oxidative characterization of Liquid Phase Epitaxy (LPE) HgCdTe epilayer has been studied by X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). HgCdTe surface is exposed by various processing steps. After measurement and analysis, we draw a conclusion that the native oxide film can be reduced and removed by the solution of lactic acid in ethylene glycol after being etched by bromine in absolute ethyl alcohol. The result shows the main optical and electrical parameters have not been changed after the treatment and the processing method given here can successfully remove the native oxides of LPE HgCdTe epilayer to obtain a clean surface. It indicates that the pre-treatment before HgCdTe surface passivation can affect the passivant/HgCdTe interface properties.

  6. Band alignment of TiO{sub 2}/FTO interface determined by X-ray photoelectron spectroscopy: Effect of annealing

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Haibo, E-mail: hbfan@nwu.edu.cn, E-mail: liusz@snnu.edu.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); School of Physics, Northwest University, Xi’an 710069 (China); Yang, Zhou; Ren, Xianpei; Gao, Fei [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Yin, Mingli [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); School of Science, Xi’an Technological University, Xi’an, Shaanxi 710062 (China); Liu, Shengzhong, E-mail: hbfan@nwu.edu.cn, E-mail: liusz@snnu.edu.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Dalian Institute of Chemical Physics, Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian, 116023 (China)

    2016-01-15

    The energy band alignment between pulsed-laser-deposited TiO{sub 2} and FTO was firstly characterized using high-resolution X-ray photoelectron spectroscopy. A valence band offset (VBO) of 0.61 eV and a conduction band offset (CBO) of 0.29 eV were obtained across the TiO{sub 2}/FTO heterointerface. With annealing process, the VBO and CBO across the heterointerface were found to be -0.16 eV and 1.06 eV, respectively, with the alignment transforming from type-I to type-II. The difference in the band alignment is believed to be dominated by the core level down-shift of the FTO substrate, which is a result of the oxidation of Sn. Current-voltage test has verified that the band alignment has a significant effect on the current transport of the heterojunction.

  7. 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.

  8. Band alignment of HfO2/AlN heterojunction investigated by X-ray photoelectron spectroscopy

    Science.gov (United States)

    Ye, Gang; Wang, Hong; Ji, Rong

    2016-04-01

    The band alignment between AlN and Atomic-Layer-Deposited (ALD) HfO2 was determined by X-ray photoelectron spectroscopy (XPS). The shift of Al 2p core-levels to lower binding energies with the decrease of take-off angles θ indicated upward band bending occurred at the AlN surface. Based on the angle-resolved XPS measurements combined with numerical calculations, valence band discontinuity ΔEV of 0.4 ± 0.2 eV at HfO2/AlN interface was determined by taking AlN surface band bending into account. By taking the band gap of HfO2 and AlN as 5.8 eV and 6.2 eV, respectively, a type-II band line-up was found between HfO2 and AlN.

  9. Band alignment of TiO2/FTO interface determined by X-ray photoelectron spectroscopy: Effect of annealing

    International Nuclear Information System (INIS)

    The energy band alignment between pulsed-laser-deposited TiO2 and FTO was firstly characterized using high-resolution X-ray photoelectron spectroscopy. A valence band offset (VBO) of 0.61 eV and a conduction band offset (CBO) of 0.29 eV were obtained across the TiO2/FTO heterointerface. With annealing process, the VBO and CBO across the heterointerface were found to be -0.16 eV and 1.06 eV, respectively, with the alignment transforming from type-I to type-II. The difference in the band alignment is believed to be dominated by the core level down-shift of the FTO substrate, which is a result of the oxidation of Sn. Current-voltage test has verified that the band alignment has a significant effect on the current transport of the heterojunction

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

    Science.gov (United States)

    Lou, Leo; Nelson, Alan E.; Heo, Giseon; Major, Paul W.

    2008-08-01

    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.

  11. Investigation of Ohmic mechanism for chlorine-treated p-type GaN using x-ray photoelectron spectroscopy

    Science.gov (United States)

    Chen, Po-Sung; Lee, Ching-Ting

    2006-08-01

    To investigate the function and mechanism of oxidation, the surface of the chlorine-treated p-type GaN semiconductor was analyzed using x-ray photoelectron spectroscopy. The chlorinated surface treatment was performed by electrolyzing HCl chemical solution to generate HClO, which in turn could be used to oxidize the p-type GaN. The chlorinated surface treatment enhances the formation of GaOx on the GaN surface and removing GaOx layer from the surface thereafter leads to the creation of additional Ga vacancies. Consequently, more holes are generated as a result of the generated Ga vacancies. Therefore, a relatively higher Ohmic performance with a specific contact resistance of 6.1×10-6Ωcm2 can be obtained for Ni /Au metal contact subsequently patterned on the chlorine-treated p-type GaN via the enhanced formation of GaOx.

  12. An X-ray photoelectron spectroscopy study of the surface of the ZnSe - CdSe system

    International Nuclear Information System (INIS)

    The results of investigation into physicochemical surface properties of solid solutions in the ZnSe - CdSe system are presented. Structure, chemical composition, degree and character of the interaction with different media are studied. The system was studied by means of X-ray photoelectron spectroscopy. The surface properties of the ZnSe - CdSe solid solutions were demonstrated by the example of Cd0.5Zn0.5 Se. The most polar selenium-cadmium bond comprises E = 53.3 eV for the ZnSe - CdSe system. The observed chemical shift as 1.0 eV may be explained by the surface peculiarities of the solid solution

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

    International Nuclear Information System (INIS)

    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

  14. X-ray photoelectron spectroscopy analysis of cleaning procedures for synchrotron radiation beamline materials at the Advanced Photon Source

    International Nuclear Information System (INIS)

    TZM (a high temperature molybdenum alloy), machinable tungsten, and 304 stainless steel were cleaned using environmentally safe, commercially available cleaning detergents. The surface cleanliness was evaluated by x-ray photoelectron spectroscopy (XPS). It was found that a simple alkaline detergent is very effective at removal of organic and inorganic surface contaminants or foreign particle residue from machining processes. The detergent can be used with ultrasonic agitation at 140 F to clean the TZM molybdenum, machinable tungsten, and 304 stainless steel. A citric-acid-based detergent was also found to be effective at cleaning metal oxides, such as iron oxide, molybdenum oxide, as well as tungsten oxides at mild temperatures with ultrasonic agitation, and it can be used to replace strong inorganic acids to improve cleaning safety and minimize waste disposal and other environmental problems. The efficiency of removing the metal oxides depends on both cleaning temperature and time

  15. An X-ray photoelectron spectroscopy study of the hydration of C{sub 2}S thin films

    Energy Technology Data Exchange (ETDEWEB)

    Rheinheimer, Vanessa, E-mail: ceevr@nus.edu.sg [Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576 (Singapore); Casanova, Ignasi [Department of Construction Engineering, Institute for Energy Technologies (INTE) and Center for Research in Nanoengineering, Universitat Politècnica de Catalunya—BarcelonaTech, Campus Nord, B1-109C, 08034 Barcelona (Spain)

    2014-06-01

    Electron-beam evaporation was used to produce thin films of β-dicalcium silicate. Chemical and mineralogical compositions were characterized by X-ray photoelectron spectroscopy (XPS) and grazing-angle X-ray diffraction (GAXRD), respectively. Results show that no fractionation occurs during evaporation and isostructural condensation of the material as synthesized films have the same composition as the initial bulk material. Samples were gradually hydrated under saturated water spray conditions and analyzed with XPS. Polymerization of the silicate chains due to hydration, and subsequent formation of C-S-H, has been monitored through evaluation of energy shifts on characteristic silicon peaks. Quantitative analyses show changes on the surface by the reduction of the Ca/Si ratio and an increase on the difference between binding energies of bridging and non-bridging oxygen. Finally, SEM/FIB observation shows clear differences between the surface and cross section of the initial sample and the reacted sample.

  16. 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.

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

    Science.gov (United States)

    2016-01-01

    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. PMID:27429041

  18. 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

    2016-08-01

    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. PMID:27429041

  19. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ananya; Matthews, Edward M.; Dessent, Caroline E. H., E-mail: caroline.dessent@york.ac.uk, E-mail: xuebin.wang@pnnl.gov [Department of Chemistry, University of York, Heslington, York YO10 5DD (United Kingdom); Hou, Gao-Lei; Wang, Xue-Bin, E-mail: caroline.dessent@york.ac.uk, E-mail: xuebin.wang@pnnl.gov [Physical Sciences Division, Pacific Northwest National Laboratory, MS K8-88, P.O. Box 999, Richland, Washington 99352 (United States)

    2015-11-14

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ∼1.7 eV, values that are lower than the RCB of the uncomplexed PtCl{sub 6}{sup 2−} dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl{sub 6}{sup 2−} ⋅ thymine and PtCl{sub 6}{sup 2−} ⋅ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN){sub 4}{sup 2−} ⋅ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl{sub 6}{sup 2−} ⋅ nucleobase spectra obtained in this work, as for the previously studied Pt(CN){sub 4}{sup 2−} ⋅ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to

  20. Attosecond Nonlinear Optics

    International Nuclear Information System (INIS)

    We report nonlinear multiphoton processes in atoms and molecules by intense high harmonics and their applications to attosecond pulse characterization. Phase matched high harmonics by a loosely focusing geometry produce highly focusable intensity with fully spatiotemporal coherence, which is sufficient to induce nonlinear optical phenomena in the extreme ultraviolet and soft x-ray (XUV) region. With this XUV coherent light source, two-photon double ionization in He is demonstrated with 42-eV high harmonic photons. On the other hand, when intense high harmonics around 20 eV is subjected to N2 molecules, occurrence of Coulomb explosion following to two-photon double ionization is observed in attosecond temporal precision. Taking advantage of larger cross section of two-photon ionization in molecules, we successfully perform the interferometric autocorrelation of an attosecond pulse train with the ion signals produced by Coulomb explosion of nitrogen molecules. The result reveals the phase relation between attosecond pulses in the train.

  1. Probing the structural evolution of ruthenium doped germanium clusters: Photoelectron spectroscopy and density functional theory calculations

    Science.gov (United States)

    Jin, Yuanyuan; Lu, Shengjie; Hermann, Andreas; Kuang, Xiaoyu; Zhang, Chuanzhao; Lu, Cheng; Xu, Hongguang; Zheng, Weijun

    2016-07-01

    We present a combined experimental and theoretical study of ruthenium doped germanium clusters, RuGen‑ (n = 3–12), and their corresponding neutral species. Photoelectron spectra of RuGen‑ clusters are measured at 266 nm. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) are obtained. Unbiased CALYPSO structure searches confirm the low-lying structures of anionic and neutral ruthenium doped germanium clusters in the size range of 3 ≤ n ≤ 12. Subsequent geometry optimizations using density functional theory (DFT) at PW91/LANL2DZ level are carried out to determine the relative stability and electronic properties of ruthenium doped germanium clusters. It is found that most of the anionic and neutral clusters have very similar global features. Although the global minimum structures of the anionic and neutral clusters are different, their respective geometries are observed as the low-lying isomers in either case. In addition, for n > 8, the Ru atom in RuGen‑/0 clusters is absorbed endohedrally in the Ge cage. The theoretically predicted vertical and adiabatic detachment energies are in good agreement with the experimental measurements. The excellent agreement between DFT calculations and experiment enables a comprehensive evaluation of the geometrical and electronic structures of ruthenium doped germanium clusters.

  2. Pyrolysis of 3-Methoxypyridine. Detection and Characterization of the Pyrrolyl Radical by Threshold Photoelectron Spectroscopy.

    Science.gov (United States)

    Holzmeier, Fabian; Wagner, Isabella; Fischer, Ingo; Bodi, Andras; Hemberger, Patrick

    2016-07-14

    Pyrolysis of 3-methoxypyridine in a heated pyrolysis reactor was found to be an efficient way to generate the pyrrolyl radical, c-C4H4N, in the gas phase. The threshold photoelectron (TPE) spectrum of this radical was recorded using vacuum ultraviolet synchrotron radiation. The spectrum revealed a singlet ground state at 9.11 ± 0.02 eV (X̃(+ 1)A) and an excited triplet state (ã(+ 3)A) at 9.43 ± 0.05 eV. Vibrational structure was observed for both cationic states and could be assigned to ring deformation modes. Furthermore, (E)- and (Z)-1-cyanoallyl radicals were found to contribute to the TPE spectrum below 8.9 eV. In addition, we have identified two parallel decomposition channels of the pyrrolyl radical, yielding either hydrogen cyanide and propargyl radical or acetylene and cyanomethyl radical. The reaction energy profiles have also been calculated for these reactions. In addition, the dissociative photoionization of the precursor 3-methoxypyridine is reported. PMID:26698131

  3. Probing the structural evolution of ruthenium doped germanium clusters: Photoelectron spectroscopy and density functional theory calculations

    Science.gov (United States)

    Jin, Yuanyuan; Lu, Shengjie; Hermann, Andreas; Kuang, Xiaoyu; Zhang, Chuanzhao; Lu, Cheng; Xu, Hongguang; Zheng, Weijun

    2016-01-01

    We present a combined experimental and theoretical study of ruthenium doped germanium clusters, RuGen− (n = 3–12), and their corresponding neutral species. Photoelectron spectra of RuGen− clusters are measured at 266 nm. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) are obtained. Unbiased CALYPSO structure searches confirm the low-lying structures of anionic and neutral ruthenium doped germanium clusters in the size range of 3 ≤ n ≤ 12. Subsequent geometry optimizations using density functional theory (DFT) at PW91/LANL2DZ level are carried out to determine the relative stability and electronic properties of ruthenium doped germanium clusters. It is found that most of the anionic and neutral clusters have very similar global features. Although the global minimum structures of the anionic and neutral clusters are different, their respective geometries are observed as the low-lying isomers in either case. In addition, for n > 8, the Ru atom in RuGen−/0 clusters is absorbed endohedrally in the Ge cage. The theoretically predicted vertical and adiabatic detachment energies are in good agreement with the experimental measurements. The excellent agreement between DFT calculations and experiment enables a comprehensive evaluation of the geometrical and electronic structures of ruthenium doped germanium clusters. PMID:27439955

  4. Circular dichroism in valence photoelectron spectroscopy of free unoriented chiral molecules: Camphor and bromocamphor

    International Nuclear Information System (INIS)

    The circular dichroism in the photoelectron angular distribution was investigated for valence photoionization of randomly oriented pure enantiomers of camphor and bromocamphor molecules using circularly polarized light in the vacuum ultraviolet. The forward-backward electron emission spectra were recorded simultaneously with two spectrometers at several opposite angles relative to the propagation direction of the photon beam and compared for each of the two substances. Measurements were also carried out for reversed light helicity and opposite molecular handedness. For the left- and right-handed enantiomers of both molecules we observed asymmetries of comparable magnitude up to several percent. The measured asymmetry parameters vary strongly for different orbital binding energies and also for the selected photon energies in the valence region. The results for both molecules are compared. They suggest a strong influence of the final states on the asymmetry, depending on the chiral geometry of the molecular electronic structure, as well as a significant dependence on the initial states involved. They also confirm theoretical predictions describing the effect in pure electric-dipole approximation

  5. X-ray photoelectron spectroscopy of nonlinear LiB3O5 crystal

    International Nuclear Information System (INIS)

    Electronic structure of LiB3O5 crystals has been studied by the method of X-ray electron spectroscopy. The results presented show that electronic structure of the perfect LBO is determined mainly by B3O5 boron-oxygen skeleton. The crystals of LiB3O5 possess very low chemical activity. An alkali component of lithium triborate is found not to reach the crystal surface. 9 refs., 2 figs

  6. X-ray photoelectron spectroscopy (XPS) investigation of the surface film on magnesium powders.

    Science.gov (United States)

    Burke, Paul J; Bayindir, Zeynel; Kipouros, Georges J

    2012-05-01

    Magnesium (Mg) and its alloys are attractive for use in automotive and aerospace applications because of their low density and good mechanical properties. However, difficulty in forming magnesium and the limited number of available commercial alloys limit their use. Powder metallurgy may be a suitable solution for forming near-net-shape parts. However, sintering pure magnesium presents difficulties due to surface film that forms on the magnesium powder particles. The present work investigates the composition of the surface film that forms on the surface of pure magnesium powders exposed to atmospheric conditions and on pure magnesium powders after compaction under uniaxial pressing at a pressure of 500 MPa and sintering under argon at 600 °C for 40 minutes. Initially, focused ion beam microscopy was utilized to determine the thickness of the surface layer of the magnesium powder and found it to be ~10 nm. The X-ray photoelectron analysis of the green magnesium sample prior to sintering confirmed the presence of MgO, MgCO(3)·3H(2)O, and Mg(OH)(2) in the surface layer of the powder with a core of pure magnesium. The outer portion of the surface layer was found to contain MgCO(3)·3H(2)O and Mg(OH)(2), while the inner portion of the layer is primarily MgO. After sintering, the MgCO(3)·3H(2)O was found to be almost completely absent, and the amount of Mg(OH)(2) was also decreased significantly. This is postulated to occur by decomposition of the compounds to MgO and gases during the high temperature of sintering. An increase in the MgO content after sintering supports this theory. PMID:22524956

  7. Time-resolved photoemission by attosecond streaking: extraction of time information

    OpenAIRE

    Nagele, S; Pazourek, R; Feist, J.; Doblhoff-Dier, K; Lemell, C.; Tőkési, K; Burgdörfer, J.

    2011-01-01

    Attosecond streaking of atomic photoemission holds the promise to provide unprecedented information on the release time of the photoelectron. We show that attosecond streaking phase shifts indeed contain timing (or spectral phase) information associated with the Eisenbud-Wigner-Smith time delay matrix of quantum scattering. However, this is only accessible if the influence of the streaking infrared (IR) field on the emission process is properly accounted for. The IR probe field can strongly m...

  8. X-ray absorption and resonant photoelectron spectroscopy of epitaxial Fe-doped SrTiO3

    International Nuclear Information System (INIS)

    In recent years resistive switching in transition metal oxides received a lot of research interest due to the proposed application as non-volatile data memory. SrTiO3 serves as a model system for the investigation of resistive switching due to the valency change mechanism. Frequently, slightly Fe doping is used, as it has shown to improve the switching properties. The focus of this study is the effect of Fe-doping of SrTiO3 in thin epitaxial films. Thin film samples with Fe concentration of 2 at.% and 5 at.% were prepared by pulsed laser deposition at varying substrate temperatures. The surface morphology of the films is studied with AFM. X-ray absorption spectroscopy is performed in total-electron and auger-electron yield offering different probing depths. Significant variations of the Fe-L edge between bulk and interface as well as after annealing are observed and discussed in terms of integration into the lattice and evolution of secondary phases. Resonant photoelectron spectroscopy at the absorption edge of Ti, O and Fe was used to determine the spectral contributions to the valence band. Most noteworthy we find significant spectral weight above the valence band, which can be attributed to Fe-states.

  9. ANALYSIS OF PASSIVATED SURFACES FOR MASS SPECTROMETER INLET SYSTEMS BY AUGER ELECTRON AND X-RAY PHOTOELECTRON SPECTROSCOPY

    Energy Technology Data Exchange (ETDEWEB)

    Ajo, H.; Clark, E.

    2010-09-01

    Stainless steel coupons approximately 0.5' in diameter and 0.125' thick were passivated with five different surface treatments and an untreated coupon was left as a control. These surface treatments are being explored for use in tritium storage containers. These coupons were made to allow surface analysis of the surface treatments using well-know surface analysis techniques. Depth profiles using Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were performed on these coupons to characterize the surface and near surface regions. Scanning electron microscope (SEM) images were collected as well. All of the surface treatments studied here appear to change the surface morphology dramatically, as evidenced by lack of tool marks on the treated samples. In terms of the passivation treatment, Vendors A-D appeared to have oxide layers that were very similar in thickness to each other (0.7-0.9 nm thick) as well as the untreated samples (the untreated sample oxide layers appeared to be somewhat larger). Vendor E's silicon coating appears to be on the order of 200 nm thick.

  10. X-ray photoelectron spectroscopy study of the stability of Fomblin Z25 on the native oxide of aluminum

    Science.gov (United States)

    Herrera-Fierro, Pilar; Pepper, Stephen V.; Jones, William R.

    1992-01-01

    Thin films of Fomblin Z25, a perfluoropolyalkylether lubricant, were vapor deposited onto clean, oxidized aluminum, and onto sapphire surfaces, and their behavior at different temperatures was studied using X-ray photoelectron spectroscopy and temperature desorption spectroscopy (TDS). The interfacial fluid molecules decompose on the native oxide at room temperature, and continue to decompose at elevated temperatures, as previous studies had shown to occur on the clean metal. TDS indicated that different degradation mechanisms were operative for clean and oxidized aluminum. On sapphire substrates, no reaction was observed at room temperature. The native oxide of aluminum is neither passive nor protective towards Fomblin Z25. At higher temperatures (150 C), degradation of the polymer on sapphire produced a debris layer at the interface with a chemical composition similar to the one formed on aluminum oxide. Rubbing a Fomblin film on a single crystal sapphire also induced the decomposition of the lubricant in contact with the interface and the formation of a debris layer.

  11. Spin state and satellite structures of ε-Fe.sub.2./sub.O.sub.3./sub. as determined by resonant photoelectron spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Schmeißer, D.; Haeberle, J.; Richter, M.; Brázda, Petr

    2015-01-01

    Roč. 364, Dec (2015), 127-131. ISSN 0168-583X R&D Projects: GA ČR GAP204/10/0035 Institutional support: RVO:68378271 Keywords : resonant photoelectron spectroscopy, * ε-Fe 2 O 3 * satellite emission Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.124, year: 2014

  12. X-Ray Photoelectron Spectroscopy Study of the Effect of Hydrocarbon Contamination on Poly(Tetrafluoroethylene) Exposed to a Nitrogen Plasma

    Science.gov (United States)

    Golub, Morton A.; Lopata, Eugene S.; Finney, Lorie S.

    1993-01-01

    It has been shown that unless the surface of poly(tetrafluoroethylene)(PTFE) is free of hydrocarbon contamination, anomalous changes in the oxygen and fluorine contents, as measured by X-ray photoelectron spectroscopy (XPS), and hence also the surface properties, may be improperly ascribed to a PTFE film exposed to a oxygen plasma.

  13. Surface alloying in the Sn/Ni(111) system studied by synchrotron radiation photoelectron valence band spectroscopy and ab-initio density of states calculations

    Czech Academy of Sciences Publication Activity Database

    Karakalos, S.; Ladas, S.; Janeček, P.; Šutara, F.; Nehasil, V.; Tsud, N.; Prince, K.; Matolín, V.; Cháb, Vladimír; Papanicolaou, N.I.; Dianat, A.; Gross, A.

    2008-01-01

    Roč. 516, č. 10 (2008), s. 2962-2965. ISSN 0040-6090 Institutional research plan: CEZ:AV0Z10100521 Keywords : surface alloys * electronic structure calculations * photoelectron spectroscopy * synchrotron radiation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.884, year: 2008

  14. Laser induced changes of As.sub.50./sub.Se.sub.50./sub. nanolayers studied by synchrotron radiation photoelectron spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Kondrat, O.; Popovich, N.; Holomb, R.; Mitsa, V.; Lyamayev, V.; Tsud, N.; Cháb, Vladimír; Matolín, V.; Prince, K. C.

    2012-01-01

    Roč. 520, č. 24 (2012), s. 7224-7229. ISSN 0040-6090 R&D Projects: GA MŠk(CZ) LC06058 Institutional support: RVO:68378271 Keywords : chalcogenide glass * photostructural changes * photoelectron spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.604, year: 2012

  15. Atomic and molecular phases through attosecond streaking

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2011-01-01

    In attosecond streaking, an electron is released by a short xuv pulse into a strong near infrared laser field. If the laser couples two states in the target, the streaking technique, which allows for a complete determination of the driving field, also gives an accurate measurement of the relative...... phase of the atomic or molecular ionization matrix elements from the two states through the interference from the two channels. The interference may change the phase of the photoelectron streaking signal within the envelope of the infrared field, an effect to be accounted for when reconstructing short...

  16. 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.)

  17. Photoelectron spectroscopy study of Fe-diluted Au-Fe alloys

    International Nuclear Information System (INIS)

    The electronic structure of Fe-diluted Au-Fe alloys has been studied by taking core-level and valence-band spectra using x-ray photoemission spectroscopy and synchrotron radiation. From the core-level spectroscopy, we found that the Fe 2p spectrum is composed of d6 and d7 multiplets from Fe impurity atoms. This behaviour is qualitatively discussed within the context of electron-electron interaction. In order to explore the electron-correlation effects in the valence band, we obtained Fe 3d partial spectral weights by taking advantage of the Cooper-minimum phenomenon of an Au 5d photoionization cross section. It was found that the spin-down states have an appreciable amount of spectral weights throughout the host Au 5d band, contrary to previous one-electron calculations predicting two-peak structure of the Fe 3d states. We suggest that this discrepancy results from the correlation effect of the Fe 3d electrons

  18. Introduction to attosecond delays in photoionization

    International Nuclear Information System (INIS)

    This tutorial presents an introduction to the interaction of light and matter on the attosecond timescale. Our aim is to detail the theoretical description of ultra-short time delays and to relate these to the phase of extreme ultraviolet (XUV) light pulses and to the asymptotic phaseshifts of photoelectron wave packets. Special emphasis is laid on time-delay experiments, where attosecond XUV pulses are used to photoionize target atoms at well-defined times, followed by a probing process in real time by a phase-locked, infrared laser field. In this way, the laser field serves as a ‘clock’ to monitor the ionization event, but the observable delays do not correspond directly to the delay associated with single-photon ionization. Instead, a significant part of the observed delay originates from a measurement induced process, which obscures the single-photon ionization dynamics. This artefact is traced back to a phaseshift of the above-threshold ionization transition matrix element, which we call the continuum-continuum phase. It arises due to the laser-stimulated transitions between Coulomb continuum states. As we shall show here, these measurement-induced effects can be separated from the single-photon ionization process, using analytical expressions of universal character, so that eventually the attosecond time delays in photoionization can be accessed.

  19. A novel X-ray photoelectron spectroscopy study of the Al/SiO2 interface

    Science.gov (United States)

    Hecht, M. H.; Vasquez, R. P.; Grunthaner, F. J.; Zamani, N.; Maserjian, J.

    1985-01-01

    The nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is reported. Both X-ray phototelectron spectroscopy (XPS) and electrical measurements of unannealed, resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Post metallization annealing at 450 C induces reduction of the SiO2 by the aluminum, at a rate consistent with the bulk reaction rate. The XPS measurement is performed from the SiO2 side after the removal of the Si substrate with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and related interfaces.

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

    International Nuclear Information System (INIS)

    Barium vanadophosphate glasses, having composition 50BaO–xV2O5–(50 − x)P2O5, (x = 0–50 mol%), were prepared by conventional melt quench method. Density, molar volume and glass transition temperature (Tg) were measured as a function of V2O5 content. Structural investigation was done using XPS and FTIR spectroscopy. First, substitution of the P2O5 by the V2O5 in the metaphosphate 50BaO–50P2O5 glass increases the density and Tg and decreases the molar volume. When the amount of V2O5 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% V2O5 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 V2O5 for P2O5. • 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

  1. Applications of Elliptically Polarized, Few-Cycle Attosecond Pulses

    Science.gov (United States)

    Starace, Anthony F.

    2016-05-01

    Use of elliptically-polarized light opens the possibility of investigating effects that are not accessible with linearly-polarized pulses. This talk presents two new physical effects that are predicted for ionization of the helium atom by few-cycle, elliptically polarized attosecond pulses. For double ionization of He by an intense elliptically polarized attosecond pulse, we predict a nonlinear dichroic effect (i.e., the difference of the two-electron angular distributions in the polarization plane for opposite helicities of the ionizing pulse) that is sensitive to the carrier-envelope phase, ellipticity, peak intensity I, and temporal duration of the pulse. For single ionization of He by two oppositely circularly polarized, time-delayed attosecond pulses we predict that the photoelectron momentum distributions in the polarization plane have helical vortex structures that are exquisitely sensitive to the time-delay between the pulses, their relative phase, and their handedness. Both of these effects manifest the ability to control the angular distributions of the ionized electrons by means of the attosecond pulse parameters. Our predictions are obtained numerically by solving the six-dimensional two-electron time-dependent Schrödinger equation for the case of elliptically polarized attosecond pulses. They are interpreted analytically by means of perturbation theory analyses of the two ionization processes. This work is supported in part by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Award No. DE-FG03-96ER14646.

  2. 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.

  3. Photoelectron spectra of actinide compounds

    International Nuclear Information System (INIS)

    A brief overview of the application of photoelectron spectroscopy is presented for the study of actinide materials. Phenomenology as well as specific materials are discussed with illustrative examples

  4. X-ray photoelectron spectroscopy (XPS) of steel to see the effects of lubricant additives on its fatigue life performance

    International Nuclear Information System (INIS)

    X-ray Photoelectron Spectroscopy (XPS) was used to look at the chemistry of the lubricant steel interface, using a well known method called 'Sputter depth profiling'. Applying sputter erosion to the metal surface in steps, we are able to see layer by layer beneath the surface. XPS analysis was done on the outer case of roller bearing called the cup section. Five different lubricants were used on the bearings. They all contaminated the base SAE 20 mineral oil with different additives packages. We have run XPS on the sputtered and un sputtered samples cut from the upper section A (load bearing material section) and the lower material section B. The un sputtered sample showed small amount of phosphorus and sulfur but high peak intensity in silicon. After sputtering for a total time of 23 hours, in half hour steps, we concluded that there was no chemistry to be seen at the depth beyond 0.2 micrometers. Another set of experiments in obtaining sputtered depth profiles were therefore done with a weaker gun using sample current lesser than that of stronger gun. This enabled us to see the appearance and gradual disappearance of Si, P, S, and halogen peaks and thereby better understand the chemistry of interface. (author)

  5. 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.

  6. X-ray photoelectron spectroscopy and micro-Raman analysis of conductive RuO2 thin films

    Science.gov (United States)

    Bhaskar, S.; Dobal, P. S.; Majumder, S. B.; Katiyar, R. S.

    2001-03-01

    Ruthenium oxide (RuO2) was synthesized in thin film and powder forms using the solution chemistry technique. The oxide electrodes on Si substrates were characterized in terms of their structure, composition, stoichiometry, and conductivity. X-ray lattice parameter calculations and micro-Raman analysis revealed the rutile structure in the material. Both films and powders exhibited an unassigned Raman band at about 477 cm-1 in their Raman spectra. Performing peak frequency calculations for B2g and A1g modes of RuO2 using the rigid-ion model, which ruled out the possibility that this band originated from disorder induced symmetry, allowed silent mode. Based on the x-ray photoelectron spectroscopy (XPS) and temperature dependent Raman studies, this band was assigned to hydrated RuO2. XPS characterizations of our samples revealed minute surface contamination of oxygen and chlorine, probably due to the film preparation and high temperature deposition processes. Films with uniform microstructure, low surface roughness, and good electrical properties meet the requirements for serving as the bottom electrode for the ferroelectric capacitor.

  7. X-ray photoelectron spectroscopy study of fluorine-treated YBa2Cu3O7-δ crystals

    International Nuclear Information System (INIS)

    An x-ray photoelectron-spectroscopy study of flux-grown YBa2Cu3O7-δ 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 BaCO3, YOH, and/or YCO3 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 Eb. In the F 1s region, the peak corresponding to those bondings is observed around Eb 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 1s envelope, chemisorbed fluoro species with Eb 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 (Eb congruent 689 eV) which can be ascribed to the formation of surface ''carbon fluoride.''

  8. Bias induced Cu ion migration behavior in resistive change memory structure observed by hard X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The Cu ion migration behavior of a Pt/Cu/HfO2/Pt structure, which is an oxide-based resistive random access memory (ReRAM) and exhibits resistance switching behavior at voltages of ±0.8 V, was investigated by hard X-ray photoelectron spectroscopy under a bias operation. A forward bias application, during switching from a high resistive state (HRS) to a low resistive state, reduced the Cu2O bonding state at the interface and the intensity ratio of Cu 2p3/2/Hf 3d5/2 (Cu/Hf) by 23 ± 5%, providing evidence of reductions in unintentionally formed Cu2O and Cu diffusion into the HfO2 layer. After switching to HRS again, Cu/Hf increased by 15 ± 5%, indicating that the Cu ion moved back to the top electrode side, though oxygen showed no bias voltage dependence. Consequently, the Cu ion has a key role in the switching. We directly observed the Cu migration behavior related to the resistive change at the Cu/HfO2 interface under bias operation. (author)

  9. X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

    Science.gov (United States)

    Bakare, M. S.; Voisey, K. T.; Roe, M. J.; McCartney, D. G.

    2010-11-01

    There is a well known performance gap in corrosion resistance between thermally sprayed corrosion resistant coatings and the equivalent bulk materials. Interconnected porosity has an important and well known effect, however there are additional relevant microstructural effects. Previous work has shown that a compositional difference exists between the regions of resolidified and non-melted material that exist in the as-sprayed coatings. The resolidified regions are depleted in oxide forming elements due to formation of oxides during coating deposition. Formation of galvanic cells between these different regions is believed to decrease the corrosion resistance of the coating. In order to increase understanding of the details of this effect, this work uses X-ray photoelectron spectroscopy (XPS) to study the passive films formed on thermally sprayed coatings (HVOF) and bulk Inconel 625, a commercially available corrosion resistant Ni-Cr-Mo-Nb alloy. Passive films produced by potentiodynamic scanning to 400 mV in 0.5 M sulphuric acid were compared with air-formed films. The poorer corrosion performance of the thermally sprayed coatings was attributed to Ni(OH) 2, which forms a loose, non-adherent and therefore non-protective film. The good corrosion resistance of wrought Inconel 625 is due to formation of Cr, Mo and Nb oxides.

  10. 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.

  11. Chemical analysis of semiconducting and metallic SmS thin films by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    We studied the chemical state of semiconducting and metallic SmS thin films by X-ray photoelectron spectroscopy (XPS), which were fabricated using dual-target magnetron sputtering by controlling the power applied to both metal and chalcogenide targets. On the basis of the valence band spectra obtained, it was suggested that semiconducting SmS has the final state corresponding to the Sm2+(4f6) configuration below the Fermi level, and metallic SmS has mainly the Sm3+(4f5) final state and a virtual band state in the Sm 5d band, contributing to the delocalization of 4f electrons and the emergence of metallic conductivity (4f6d0-4f5d1). Thus, the spectra of our fabricated SmS thin films correspond to the band structure obtained from the dielectric property. This is the first work performed on the intrinsically prepared metallic SmS while the former works done for the sample transformed from semiconductor to metal phase by hard polishing

  12. X-Ray photoelectron spectroscopy and diffractometry of MnOx catalysts: surface to bulk composition relationships

    International Nuclear Information System (INIS)

    Surface and bulk analyses of variously-composed, synthetic MnOx catalysts were carried out by means of X-ray photoelectron spectroscopy (XPS) and diffractometry (XRD), respectively. The data obtained were processed for a comprehensive assessment of bulk and surface compositions, surface oxidation state, and crystalline size. The XPS data processing revealed that a credible assessment of the surface composition (MnOx(OH)y(OH2)z necessitates: (i) the implementation of experimental sensitivity factors determined on a local reference surface maintaining a close chemical similarity to the test materials, and (ii) the fine evaluation of contributions of various oxygen-containing surface species to the O 1s electron emission. The most prominent result of the present investigation is that the exposure of the bulk composition at the surface is quite proportioned. Such a surface to bulk intimacy is thought to enable genesizing the surface composition appropriate for certain catalytic and selectivity, via a possible control over the bulk formation events. (orig.)

  13. 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.

  14. A high pressure x-ray photoelectron spectroscopy study of CO oxidation over Rh(100)

    International Nuclear Information System (INIS)

    We have studied the oxidation of CO over Rh(100) using high pressure x-ray photoelectron spectroscopy under CO and O2 pressures ranging from 0.01 to 1 mbar. The results show a very low or no conversion for the CO covered surface found at low temperatures, while the activity rises slightly when the temperature is high enough for some CO to desorb, exposing surface sites for dissociative O2 adsorption. As the temperature is increased further, more CO desorbs and oxygen replaces CO as the dominating species at the surface. At the same time we find a sudden increase in the reactivity, such that all CO that reaches the surface is instantly transformed into CO2. We find that the O coverage in the active state is highly dependent on the total pressure and, although we do not detect any presence of a surface oxide as in previous surface x-ray diffraction studies, the highest O coverage indicates that the surface is close to being oxidized. (paper)

  15. Investigation of the grain-boundary chemistry in used CANDU fuel by x-ray photoelectron spectroscopy (XPS)

    International Nuclear Information System (INIS)

    The grain-boundary chemistry of used CANDU fuel is being systematically investigated by X-ray photoelectron spectroscopy (XPS) using a McPherson ESCA-36 instrument that has been adapted for routine studies of highly radioactive materials. Initial stages of fuel corrosion under various storage and disposal conditions can be identified from chemical-shift effects for uranium. For example, pervasive but highly selective grain-boundary oxidation has been revealed in CANDU fuels exposed to moist air at 150 deg. C for extended periods, suggesting aggressive radiolytic processes operating in a thin film of adsorbed water. Pronounced segregation of a number of fission products to cracks and grain boundaries in used CANDU fuels has been explicitly demonstrated by XPS as well. Model calculations and composition depth profiles are indicative of near monolayer films. Some correlations between fuel power history and fission-product distributions have been established and possible evidence of migration during moist-air exposure has been obtained. The key advantages and limitations of XPS in this context are discussed and illustrated with selected results. (author). 23 refs, 8 figs, 1 tab

  16. Effect of interface layers on phase-change recording material analyzed by hard X-ray photoelectron spectroscopy method

    International Nuclear Information System (INIS)

    The influence of interface layers on the chemical and electronic states of a phase-change recording material, GeBiTe (GBT) alloy, used in high-speed rewritable HD DVD media was investigated for the first time by hard-X-ray photoelectron spectroscopy (HX-PES). The binding state of elements for the amorphous state of the phase-change recording film with interface layers is closer to that of the crystalline state than the amorphous film without interface layers. The density of states (DOS) for the valence band of the amorphous state without an interface layer was smaller than that of the crystalline state. The band-edge energy of the amorphous state without an interface layer was lower than that of the crystalline state by about 0.5eV. On the other hand, the DOS and the band-edge energy of the amorphous state of GBT with interface layers were almost the same as those of the crystalline state. This result may lead to almost the same carrier for electrical conduction for the crystalline state as the amorphous state, which is totally unexpected, thus very interesting, because the atomic arrangements should differ from each other. We speculate that these effects are a factor allowing high-speed crystallization. (author)

  17. Laboratory hard X-ray photoelectron spectroscopy of La1−xSrxMnO3

    International Nuclear Information System (INIS)

    A laboratory hard X-ray photoelectron spectroscopy (HXPS) system equipped with a monochromatic Cr Kα (hν = 5414.7 eV) X-ray source was applied to an investigation of the core-level electronic structure of La1−xSrxMnO3. No appreciable high binding-energy shoulder in the O 1s HXPS spectra were observed while an enhanced low binding-energy shoulder structure in the Mn 2p3/2 HXPS spectra were observed, both of which are manifestation of high bulk sensitivity. Such high bulk sensitivity enabled us to track the Mn 2p3/2 shoulder structure in the full range of x, giving us a new insight into the binding-energy shift of the Mn 2p3/2 core level. Comparisons with the results using the conventional laboratory XPS (hν = 1486.6 eV) as well as those using a synchrotron radiation source (hν = 7939.9 eV) demonstrate that HXPS is a powerful and convenient tool to analyze the bulk electronic structure of a host of different compounds. (author)

  18. X-Ray Photoelectron Spectroscopy Study of the Heating Effects on Pd/6H-SiC Schottky Structure

    Science.gov (United States)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak

    1998-01-01

    X-ray photoelectron spectroscopy is used to study the effects of heat treatment on the Pd/6H-SiC Schottky diode structure. After heating the structure at 425 C for 140 h, a very thin surface layer of PdO mixed with SiO(x) formed on the palladium surface of the Schottky structure. Heat treatment promoted interfacial diffusion and reaction which significantly broadened the interfacial region. In the interfacial region, the palladium concentration decreases with depth, and the interfacial products are Pd(x)Si (x = 1,2,3,4). In the high Pd concentration regions, Pd4Si is the major silicide component while gr and Pd2Si are major components in the low Pd concentration region. At the center of the interface, where the total palladium concentration equals that of silicon, the concentrations of palladium associated with various palladium silicides (Pd(x)Si, x= 1,2,3,4) are approximately equal. The surface passivation layer composed of PdO and SiO, may significantly affect the electronic and catalytic properties of the surface of the Schottky diode which plays a major role in gas detection. The electronic properties of the Schottky structure may be dominated by a (Pd+Pd(x)Si)/SiC interface. In order to stabilize the properties of the Schottky structure the surface and interface diffusion and reactions must be controlled.

  19. 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.

  20. Membrane surface modification and characterization by X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements

    International Nuclear Information System (INIS)

    Surface modifying macromolecules (SMMs) were used to modify the top surface of polymeric membranes. SMMs are oligomeric fluoropolymers synthesized by polyurethane chemistry and tailored with fluorinated end groups. In this study, the surface of polyetherimide (PEI) flat-sheet membranes prepared by the phase inversion method was modified using 2 wt.% of SMM and 15 wt.% PEI concentration in the polymer casting solution. The effect of solvent evaporation time on membrane surface modification was investigated. X-ray photoelectron spectroscopy analysis shows enrichment of fluorine on the modified PEI membrane surfaces and their contact angles were higher than those of the unmodified PEI membrane. Both the surface fluorine content and contact angles of the SMM/PEI blended membrane increased when the solvent evaporation time was increased up to 5 min. The SMM modified and unmodified PEI membranes were characterized by means of tapping mode atomic force microscopy (TM-AFM). The mean pore size, nodule size, pore density, surface porosity and mean roughness of the modified membranes were determined and compared with those of the unmodified membrane

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

    International Nuclear Information System (INIS)

    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 Cu2S 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

  2. X-ray photoelectron spectroscopy investigation over supported palladium catalysts prepared using water-in-oil microemulsion

    International Nuclear Information System (INIS)

    Supported palladium catalysts have been prepared using water n il microemulsions consisting of Pd(NO3)2 aq, Brij 30 (surfactant) and n-hexane (oil). The binding energies of palladium from those catalysts were measured using x-ray photoelectron spectroscopy (XPS) and were compared with that of the catalysts prepared by conventional impregnation method. It was observed that the majority of the palladium is present at a binding energy shifted between 0.8 to 1.0 eV higher than the impregnation catalysts observed for PdO. Such shift appeared to be associated with a metal support interaction where the palladium was very small in size and highly dispersed. These findings were supported with a much higher activity in methane combustion under lean conditions. However, not only the size and dispersity of palladium that determined their catalytic performance, it was found that the active phase or state of the catalysts that existed during the reaction has great influence on the catalyst activity. The result showed PdO was the most active state for methane combustion but it did not rule out the possibilities of a mixed phase, Pd0/PdOx. (Author)

  3. Reduction of Vanadium Oxide (VOx) under High Vacuum Conditions as Investigated by X-Ray Photoelectron Spectroscopy

    Science.gov (United States)

    Chourasia, A.

    2015-03-01

    Vanadium oxide thin films were formed by depositing thin films of vanadium on quartz substrates and oxidizing them in an atmosphere of oxygen. The deposition was done by the e-beam technique. The oxide films were annealed at different temperatures for different times under high vacuum conditions. The technique of x-ray photoelectron spectroscopy has been employed to study the changes in the oxidation states of vanadium and oxygen in such films. The spectral features in the vanadium 2p, oxygen 1s, and the x-ray excited Auger regions were investigated. The Auger parameter has been utilized to study the changes. The complete oxidation of elemental vanadium to V2O5 was observed to occur at 700°C. At any other temperature, a mixture of oxides consisting of V2O5 and VO2 was observed in the films. Annealing of the films resulted in the gradual loss of oxygen followed by reduction in the oxidation state from +5 to 0. The reduction was observed to depend upon the annealing temperature and the annealing time. Organized Research, TAMU-Commerce.

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

    International Nuclear Information System (INIS)

    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 A2(πσ∗) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B1(π3py) Rydberg state, followed by prompt internal conversion to the A2(πσ∗) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A2(πσ∗) 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 A2(πσ∗) state, facilitating wavepacket motion around the potential barrier in the N–CH3 dissociation coordinate

  5. X-ray photoelectron spectroscopy of CeO2-Na2O-SiO2 glasses

    International Nuclear Information System (INIS)

    A series of (CeO2)x-(Na2O)0.3-(SiO2)(0.7-x) glasses, where 0.025 ≤ x ≤ 0.075, have been synthesized and investigated by mean of X-ray photoelectron spectroscopy (XPS). The Ce 3d spin-orbit doublet was curve fitted in order to quantify the proportions of each cerium oxidation state in these glasses. It was found that Ce ions are predominantly in the Ce(III) state in glasses with compositions x ≤ 0.075, while mixed Ce valences were found in the glass with composition x = 0.10. The O 1s spectra have also been curve fitted with two components, one from bridging oxygen (BO) and the other from non-bridging oxygen atoms (NBO). The measured number of NBO, based on the fact that only oxygen atoms in the site Si-O-Na+ contribute to the NBO peak, was found to be constant at ∼35% for all samples, in good agreement with the value calculated from the glass composition and inductively coupled plasma (ICP) suggesting that Ce ions enter the network as a glass intermediate. The thermal measurements done on these glasses agree well with the XPS findings

  6. Hydrosilylation of crystalline silicon (111) and hydrogenated amorphous silicon surfaces: A comparative x-ray photoelectron spectroscopy study

    International Nuclear Information System (INIS)

    Alkene molecules were covalently bonded to hydrogen-terminated crystalline silicon (111) and hydrogenated amorphous silicon (a-Si:H) surfaces by thermally induced hydrosilylation. The resulting chemical surface structure was analyzed by x-ray photoelectron spectroscopy and compared to that of the corresponding silicon surfaces covered by a native oxide and terminated with hydrogen. Our results demonstrate successful hydrosilylation on both substrate materials. However, the presence of oxygen on the surface turns out to hinder the hydrosilylation reaction, as shown by the reduced concentration of hydrocarbons on the surface after prolonged exposure of the Si substrates prior to hydrosilylation. By monitoring both the O 1s and the Si 2p peaks, the oxidation kinetics of a-Si:H was found to be diffusion limited. Since stable hydrogen termination as a prerequisite of hydrosilylation can be achieved on a-Si:H surfaces with much less technological effort than on crystalline silicon surfaces, a-Si:H is a promising substrate for biofunctionalization procedures requiring less stringent process conditions

  7. X-ray-induced beam damage observed during x-ray photoelectron spectroscopy (XPS) studies of palladium electrode ink materials

    International Nuclear Information System (INIS)

    The surface compositional characteristics of two palladium metal electrode inks, air-dried on barium titanate (BaTiO3) dielectric ceramic substrates, have been studied using x-ray photoelectron spectroscopy (XPS). It is found that exposure of the inks to the x-ray beam during the time of analysis required for data acquisition causes surface damage. Changes in the C 1s and O 1s regions in particular, which reflect modifications to the organic, polymeric binder materials present in the inks, have been integrated as a function of x-ray exposure time, incident photon energy and beam power levels. Additional complexity in the C 1s spectral envelope that cannot be explained in terms of the expected contributing organic functionalities is observed. This is explained in terms of a difference in charging effects experienced by adventitious carbon species and those intimately associated with palladium metal centres. The degree of damage induced by the x-ray beam under specific operating conditions has been compared also with that caused by exposure of the surfaces to an electron beam. Indications of the time scales and operating parameters for conducting XPS experiments on the unmodified surface, prior to surface degradation, are given. (author)

  8. Study of the initial oxidation of the U4Zr2Nb alloy by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    In this work, the initial stages of oxidation of the U4Zr2Nb alloy in O2 atmosphere were studied in-situ, in ultrahigh vacuum, by X-ray photoelectron spectroscopy (XPS), an advanced surface-sensitive technique. After several hours of Ar+ion-sputtering to surface cleanness, the O2 exposures was realized on the sample at room temperature. The evolution of oxide film formed on the sample surface was followed by XPS measures, by using Mg Kα radiation of 1253.6 eV and a CLAM-2 (Vacuum Generator) electron energy analyzer. The changes of U 4f, Nb 3d, Zr 3d and O 1s photoemission peaks with O2 exposure indicate that the adsorption of oxygen on the U4Zr2Nb alloy surface leads to fast formation of UO2. The alloying elements show slower oxidation and different compounds are observed in Nb 3d spectra analysis. This work shows an expressive enlargement of Nb 3d peak at 100 Langmuir exposure, indicating the formation of Nb2O5 and NbO in the oxide. On the other hand, the binding energy of Zr 3d suggests that the ZrO2 formation is stable as well as uranium dioxide. (author)

  9. X-ray photoelectron spectroscopy studies of MgB{sub 2} for valence state of Mg

    Energy Technology Data Exchange (ETDEWEB)

    Talapatra, A. [Department of Physics, Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700 064 (India); Bandyopadhyay, S.K. [Department of Physics, Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700 064 (India)]. E-mail: skband@veccal.ernet.in; Sen, Pintu [Department of Physics, Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700 064 (India); Barat, P. [Department of Physics, Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700 064 (India); Mukherjee, S. [Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata 700 064 (India); Mukherjee, M. [Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata 700 064 (India)

    2005-03-01

    Core level X-ray photoelectron spectroscopy (XPS) studies have been carried out on polycrystalline MgB{sub 2} pellets over the whole binding energy range with a view to having an idea of the charge state of magnesium (Mg). We observe three distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB{sub 2} and MgCO{sub 3} or, divalent Mg species, respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB{sub 2} is lower than that corresponding to Mg(2+), indicative of the fact that the charge state of Mg in MgB{sub 2} is less than (2+). Lowering of the formal charge of Mg promotes the {sigma} {yields} {pi} electron transfer in boron (B) giving rise to holes on the top of the {sigma}-band which are involved in coupling with B E{sub 2g} phonons for superconductivity. Through this charge transfer, Mg plays a positive role in hole superconductivity. B 1s spectra consist of three peaks corresponding to MgB{sub 2}, boron and B{sub 2}O{sub 3}. There is also evidence of MgO due to surface oxidation as seen from O 1s spectra.

  10. Study of the electrodeposition of rhenium thin films by electrochemical quartz microbalance and X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Rhenium thin films were prepared by electrodeposition from an aqueous solution containing 0.1 M Na2SO4+H2SO4, pH 2 in presence of y mM HReO4. As substrates polycrystalline gold (y=0.75 mM HReO4) and monocrystalline n-Si(100) (y=40 mM HReO4) were used. The electrochemical growth of rhenium was studied by cyclic voltammetry and electrochemical quartz microbalance on gold electrodes. The results found in the potential region before the hydrogen evolution reaction (her) showed that ReO3, ReO2 and Re2O3 with different hydration grades can be formed. In the potential region where the her is occurring, either on gold or n-Si(100) the electrodeposition of metallic rhenium takes place. On both substrates, rhenium films were formed by electrolysis at constant potential and X-ray photoelectron spectroscopy technique was used to characterise these deposits. It was concluded that the electrodeposited films were of metallic rhenium and only the uppermost atomic layer contained rhenium oxide species

  11. X-ray photoelectron spectroscopy on the Co film grown on the nitrogen pre-covered Cu(100) surface

    International Nuclear Information System (INIS)

    Full text: Surface structures and electronic structures have been characterized on the Co thin films grown on the nitrogen pre-covered Cu(100) surface by means mainly of the X-ray photoelectron spectroscopy (XPS). From the analysis of the XPS signal ratio of N1s/Cu2p and N1s/Cu3p, it is concluded that the most nitrogen atoms segregate onto the top of the deposited Co films, like as the case of the Co deposition on the oxygen pre-covered Cu(100) surface. While it has been known that the clean and oxygen- adsorbed Co thin film shows the satellite peaks on the Co2p spectrum with the separation of 3eV from the main peaks, we observed the separation of 4eV on the nitrogen-adsorbed Co film. Figure 1 shows the series of the XPS spectra of Co2p taken on the nitrogenadsorbed Co films with changing the Co film thickness. While the 3eV satellite is seen on the submonolayer Co film, the 4eV satellite appears on the thicker Co films ( > 4.5ML). We may ascribe this newly found 4eV satellite to the adsorbate-induced two hole binding sate, instead of the size effect suggested on the clean and oxygen-adsorbed Co film

  12. 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 ...

  13. Steering continuum electron dynamics by low-energy attosecond streaking

    Science.gov (United States)

    Geng, Ji-Wei; Xiong, Wei-Hao; Xiao, Xiang-Ru; Gong, Qihuang; Peng, Liang-You

    2016-08-01

    A semiclassical model is developed to understand the electronic dynamics in the low-energy attosecond streaking. Under a relatively strong infrared (IR) pulse, the low-energy part of photoelectrons initialized by a single attosecond pulse (SAP) can either rescatter with the ionic core and induce interferences structures in the momentum spectra of the ionized electrons or be recaptured into the Rydberg states. The Coulomb potential plays essential roles in both the electron rescattering and recapturing processes. We find that by changing the time delay between the SAP and the IR pulse, the photoelectrons yield or the population of the Rydberg states can be effectively controlled. The present study demonstrates a fascinating way to steer the electron motion in the continuum.

  14. High resolution, low hν photoelectron spectroscopy with the use of a microwave excited rare gas lamp and ionic crystal filters

    International Nuclear Information System (INIS)

    The need for not only bulk sensitive but also extremely high resolution photoelectron spectroscopy for studying detailed electronic structures of strongly correlated electron systems is growing rapidly. Moreover, easy access to such a capability in one's own laboratory is desirable. Demonstrated here is the performance of a microwave excited rare gas (Xe, Kr, and Ar) lamp combined with ionic crystal filters (sapphire, CaF2, and LiF), which can supply three strong lines near the photon energy of hnyu hν=8.4, 10.0, and 11.6 eV, with the hν resolution of better than 600 μeV for photoelectron spectroscopy. Its performance is demonstrated on some materials by means of both angle-integrated and angle-resolved measurements.

  15. Interior and interfacial aqueous solvation of benzene dicarboxylate dianions and their methylated analogues: A combined molecular dynamics and photoelectron spectroscopy study

    Czech Academy of Sciences Publication Activity Database

    Minofar, B.; Vrbka, Luboš; Mucha, Martin; Jungwirth, Pavel; Yang, X.; Wang, X. B.; Fu, Y. J.; Wang, L. S.

    2005-01-01

    Roč. 109, - (2005), s. 5042-5049. ISSN 1089-5639 R&D Projects: GA MŠk(CZ) ME 644; GA MŠk(CZ) LC512 Grant ostatní: NSF(US) CHE041312; NSF(US) CHE0209719 Institutional research plan: CEZ:AV0Z40550506 Keywords : benzene dicarboxylate dianions * molecular dynamics * photoelectron spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.898, year: 2005

  16. X-ray photoelectron spectroscopy analysis of whole cells and isolated cell walls of gram-positive bacteria: comparison with biochemical analysis.

    OpenAIRE

    Dufrêne, Yves; van der Wal, A.; Norde, W; Rouxhet, Paul

    1997-01-01

    The surface chemical composition of whole cells and isolated cell walls of four coryneform bacteria and of a Bacillus brevis strain has been determined by X-ray photoelectron spectroscopy (XPS). The XPS data were converted into concentrations of model compounds: peptides, polysaccharides, and hydrocarbonlike compounds. The composition of the surface of B. brevis differed markedly from that of coryneforms: the peptide concentration was about twice higher in the former case, which is attributed...

  17. Study of electro-chemical properties of metal-oxide interfaces using a newly constructed ambient pressure X-ray photoelectron spectroscopy endstation

    International Nuclear Information System (INIS)

    In this report, we briefly describe the general design principles and construction of a newly developed ambient pressure X-ray photoelectron spectroscopy system. This system provides an imaging mode with 2 heterojunction and Rh-TiO2 metal-support system are presented. This new system can probe structured surfaces near ambient pressure as a function of temperature, pressure, electrical potential, local position, and time. It is a valuable in situ tool to detect material transformations at the micrometer scale.

  18. Characterizing reactions to fabricate thin films of charge transfer complexes by synchrotron photoelectron spectroscopy: A case study of DCNQI-Cu

    Science.gov (United States)

    Shimada, Toshihiro; Mochida, Michihiro; Koma, Atsushi

    1997-04-01

    Ultraviolet photoelectron spectroscopy with various photon energies using synchrotron radiation was used to characterize chemical reactions associated with thin film growth of organic charge transfer complex (DMe-DCNQI) 2Cu. Other molecular systems H 2Pc, CuPc and C 60 were also studied to clarify the origin of the systematic relation between the spectra and the incident photon energy. Characteristic photon energy dependence of the photo-ionization cross section of molecular orbitals is useful to analyze the intermolecular reactions.

  19. Effects of Varied Cleaning Methods on Ni-5% W Substrate for Dip-Coating of Water-based Buffer Layers: An X-ray Photoelectron Spectroscopy Study

    OpenAIRE

    Isabel Van Driessche; Ruben Hühne; Els Bruneel; Vyshnavi Narayanan

    2012-01-01

    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 chemi...

  20. Application of the Auger and X-ray photoelectron electronic spectroscopies to the study of superficial segregation in the system Pt-Rh

    International Nuclear Information System (INIS)

    The Auger and X-ray photoelectron spectroscopies are applied to the study of the superficial segregation in the system of the binary alloy Pt-Rh. The methodology for the cleaning of the samples, which is essential for the obtainment of reproducible results, has been established. The spectra qualitative analysis allows to identify the element segregated. The application of the Gallon model permits to develop a quantitative study of the phenomenon. (S.M.)

  1. Attosecond quantum stroboscope.

    Science.gov (United States)

    Paulus, Gerhard G; Stania, Gernot

    2009-04-14

    Electron disco: A "quantum stroboscope" for capturing the electron motion on a subfemtosecond timescale for a particular class of problems is highlighted. The picture shows a diffraction pattern caused by wave packets obtained by synchronizing attosecond UV pulses to a near-IR field and ionizing rare-gas atoms. PMID:19294685

  2. X-ray photoelectron spectroscopy and electrochemical studies of mild steel FeE500 passivation in concrete simulated water

    International Nuclear Information System (INIS)

    In the context of the prediction of the long-term behaviour of reinforced concrete structures involved in the nuclear waste storage, the corrosion mechanisms of steels have to be assessed. When mild steel rebars are embedded in concrete, the chemical environment of the reinforcement is progressively modified, due to the carbonation of the concrete matrix. This modification leads to the variation of iron oxides properties formed at the steel/concrete interface, and the active corrosion can be initiated. The aim of this study is to evaluate the passivation behaviour and to provide insights into the de-passivation of mild steel in concrete pore solution. In a young concrete, due to the alkalinity of the interstitial solution, steel reinforcement remains passive. Immersion tests of mild steel substrate in various alkaline solutions (from pH 13 to 10) have been performed. Due to the low thickness of the corrosion layers formed, X-ray photoelectron spectroscopy has been used to characterize them. In the passive domain, the corrosion products are similar for the various solutions. The corrosion layer is composed of a mixture of Fe3+ and Fe2+. A similar approach is used to determine the de-passivation mechanism. The effect of various components such as carbonates, sulfates and silicates resulting from the dissolution of minerals of cement during the carbonation process is investigated. In addition to the surface analysis, the evolution of the electrochemical behaviour as function of the solution nature (pH) is evaluated with the help of electrochemical measurements (free corrosion potential, cyclic volt-amperometry). (authors)

  3. Organic heterojunctions of layered perylene and phthalocyanine dyes: characterization with UV-photoelectron spectroscopy and luminescence quenching

    Energy Technology Data Exchange (ETDEWEB)

    Alloway, Dana M.; Armstrong, Neal R. [University of Arizona, Department of Chemistry, Tucson, AZ (United States)

    2009-04-15

    We present here the characterization of organic/organic' heterojunctions created from either of two perylene dyes, perylenetetracarboxylicdianhydride (PTCDA) or the bisimide derivative perylenetetracarboxylicdianhydride-N,N'-bis (butyl)imide (C4-PTCDI), and two chloro-metallated donor phthalocyanines (ClAlPc or ClInPc). The perylene dyes were selected to create thin films with the core of the perylene dye parallel to the substrate plane (PTCDA) or nearly vertical to the substrate plane, with layer planes defined by the butyl substituents (C4-PTCDI). We compare the frontier orbital offsets revealed by UV-photoelectron spectroscopy, and quenching of luminescence of the perylene dyes, as a function of Pc coverage. The ionization potentials (IPs) of the Pc layers, the degree to which interface dipoles are formed at the Pc/perylene dye interface, and the degree of quenching of the perylene luminescence are affected by the structure of the Pc/perylene interface. Pc/PTCDA heterojunctions show significant interface dipoles and higher IPs for the first-deposited Pc layers compared to Pc/C4-PTCDI heterojunctions, which show negligible interface dipoles and lower overall IP values for initial Pc layers. Luminescence of the selectively excited perylene layers is quenched by the addition of even submonolayer coverages of Pc. This quenching process occurs as a result of both energy transfer (perylene to Pc) and charge transfer (Pc to perylene). Luminescence from monomeric and aggregated ClAlPc and ClInPc monolayers is seen on C4-PTCDI films, whereas only luminescence from the aggregated forms of these Pcs is seen on PTCDA films. These studies reveal aspects of organic heterojunction energetics which may have important implications for organic solar cell design. (orig.)

  4. 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.

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

    International Nuclear Information System (INIS)

    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

  6. X-ray photoelectron spectroscopy study of the growth kinetics of biomimetically grown hydroxyapatite thin-film coatings

    Science.gov (United States)

    McLeod, K.; Kumar, S.; Dutta, N. K.; Smart, R. St. C.; Voelcker, N. H.; Anderson, G. I.

    2010-09-01

    Hydroxyapatite (HA) thin-film coatings grown biomimetically using simulated body fluid (SBF) are desirable for a range of applications such as improved fixation of fine- and complex-shaped orthopedic and dental implants, tissue engineering scaffolds and localized and sustained drug delivery. There is a dearth of knowledge on two key aspects of SBF-grown HA coatings: (i) the growth kinetics over short deposition periods, hours rather than weeks; and (ii) possible difference between the coatings deposited with and without periodic SBF replenishment. A study centred on these aspects is reported. X-ray photoelectron spectroscopy (XPS) has been used to study the growth kinetics of SBF-grown HA coatings for deposition periods ranging from 0.5 h to 21 days. The coatings were deposited with and without periodic replenishment of SBF. The XPS studies revealed that: (i) a continuous, stable HA coating fully covered the titanium substrate after a growth period of 13 h without SBF replenishment; (ii) thicker HA coatings about 1 μm in thickness resulted after a growth period of 21 days, both with and without SBF replenishment; and (iii) the Ca/P ratio at the surface of the HA coating was significantly lower than that in its bulk. No significant difference between HA grown with and without periodic replenishment of SBF was found. The coatings were determined to be carbonated, a characteristic desirable for improved implant fixation. The atomic force and scanning electron microscopies results suggested that heterogeneous nucleation and growth are the primary deposition mode for these coatings. Primary osteoblast cell studies demonstrated the biocompatibility of these coatings, i.e., osteoblast colony coverage of approximately 80%, similar to the control substrate (tissue culture polystyrene).

  7. X-ray photoelectron spectroscopy study of the growth kinetics of biomimetically grown hydroxyapatite thin-film coatings

    International Nuclear Information System (INIS)

    Hydroxyapatite (HA) thin-film coatings grown biomimetically using simulated body fluid (SBF) are desirable for a range of applications such as improved fixation of fine- and complex-shaped orthopedic and dental implants, tissue engineering scaffolds and localized and sustained drug delivery. There is a dearth of knowledge on two key aspects of SBF-grown HA coatings: (i) the growth kinetics over short deposition periods, hours rather than weeks; and (ii) possible difference between the coatings deposited with and without periodic SBF replenishment. A study centred on these aspects is reported. X-ray photoelectron spectroscopy (XPS) has been used to study the growth kinetics of SBF-grown HA coatings for deposition periods ranging from 0.5 h to 21 days. The coatings were deposited with and without periodic replenishment of SBF. The XPS studies revealed that: (i) a continuous, stable HA coating fully covered the titanium substrate after a growth period of 13 h without SBF replenishment; (ii) thicker HA coatings about 1 μm in thickness resulted after a growth period of 21 days, both with and without SBF replenishment; and (iii) the Ca/P ratio at the surface of the HA coating was significantly lower than that in its bulk. No significant difference between HA grown with and without periodic replenishment of SBF was found. The coatings were determined to be carbonated, a characteristic desirable for improved implant fixation. The atomic force and scanning electron microscopies results suggested that heterogeneous nucleation and growth are the primary deposition mode for these coatings. Primary osteoblast cell studies demonstrated the biocompatibility of these coatings, i.e., osteoblast colony coverage of approximately 80%, similar to the control substrate (tissue culture polystyrene).

  8. Atomic force microscopy and X-ray photoelectron spectroscopy evaluation of adhesion and nanostructure of thin Cr films

    International Nuclear Information System (INIS)

    Chromium (Cr) thin films were deposited on float glass using electron beam (e-beam) physical vapor deposition and radio frequency (RF) magnetron sputtering techniques. Surface morphology of these Cr films was studied using atomic force microscopy (AFM). The e-beam deposited Cr films consisted of isolated surface mounds while in RF sputtered samples, these mounds combined to form larger islands. Lower surface adhesive properties were observed for e-beam deposited films, as determined from AFM force–distance curves, presumably due to the nanostructural differences. Similar amounts of adsorbed atmospheric carbonaceous contaminants and water vapor were detected on samples deposited using both methods with e-beam deposited samples having additional carbide species, as determined by X-ray photoelectron spectroscopy data. The dominant crystallographic plane in both e-beam deposited and RF sputtered Cr thin films was (110) of body-centered cubic Cr metal structure as determined from X-ray diffraction data. Weak (211) reflection was also observed in RF sputtered samples and was attributed to a different thin Cr film condensation and growth mechanism which resulted in nanostructural differences between films deposited using two different methods. - Highlights: ► Cr thin films were deposited on glass using different vacuum deposition methods. ► Surface morphological, chemical, adhesive and structural properties were studied. ► The e-beam deposited Cr thin films consisted of isolated surface mounds. ► In RF magnetron sputtered samples, surface mounds combined to form larger islands. ► Variations in surface adhesive force were due to nanostructural differences.

  9. X-ray photoelectron spectroscopy study of the growth kinetics of biomimetically grown hydroxyapatite thin-film coatings

    Energy Technology Data Exchange (ETDEWEB)

    McLeod, K. [Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Kumar, S., E-mail: sunil.kumar@unisa.edu.au [Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Dutta, N.K. [Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Smart, R.St.C. [Applied Centre for Structural and Synchrotron Studies, University of South Australia, Mawson Lakes, SA 5095 (Australia); Voelcker, N.H. [School of Chemistry, Physics and Earth Sciences, Flinders University of South Australia, GPO Box 2100, Adelaide 5001 (Australia); Anderson, G.I. [School of Veterinary Science, University of Adelaide, Adelaide, SA 5005 (Australia)

    2010-09-15

    Hydroxyapatite (HA) thin-film coatings grown biomimetically using simulated body fluid (SBF) are desirable for a range of applications such as improved fixation of fine- and complex-shaped orthopedic and dental implants, tissue engineering scaffolds and localized and sustained drug delivery. There is a dearth of knowledge on two key aspects of SBF-grown HA coatings: (i) the growth kinetics over short deposition periods, hours rather than weeks; and (ii) possible difference between the coatings deposited with and without periodic SBF replenishment. A study centred on these aspects is reported. X-ray photoelectron spectroscopy (XPS) has been used to study the growth kinetics of SBF-grown HA coatings for deposition periods ranging from 0.5 h to 21 days. The coatings were deposited with and without periodic replenishment of SBF. The XPS studies revealed that: (i) a continuous, stable HA coating fully covered the titanium substrate after a growth period of 13 h without SBF replenishment; (ii) thicker HA coatings about 1 {mu}m in thickness resulted after a growth period of 21 days, both with and without SBF replenishment; and (iii) the Ca/P ratio at the surface of the HA coating was significantly lower than that in its bulk. No significant difference between HA grown with and without periodic replenishment of SBF was found. The coatings were determined to be carbonated, a characteristic desirable for improved implant fixation. The atomic force and scanning electron microscopies results suggested that heterogeneous nucleation and growth are the primary deposition mode for these coatings. Primary osteoblast cell studies demonstrated the biocompatibility of these coatings, i.e., osteoblast colony coverage of approximately 80%, similar to the control substrate (tissue culture polystyrene).

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

    Science.gov (United States)

    Hassan, S.; Yusof, M. S.; Embong, Z.; Maksud, M. I.

    2016-01-01

    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 (La2O3) 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 La2O3 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 La2O3 and La(OH)3. The information of oxygen species, O2- component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O2-), two chemisorb component (La2O3) and La(OH)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.

  11. Utility and constraint on the use of pump-probe photoelectron spectroscopy for detecting time-resolved surface photovoltage

    International Nuclear Information System (INIS)

    Highlights: ► The pump-probe PES method for detecting time-resolved surface photovoltage (SPV) is analyzed. ► The simulation for the trip of the electron from the sample to the analyzer revealed its utility and constraint. ► The basic time-resolution is determined by the pump-spot radius and the electron energy. ► The lifetime of the SPV that is shorter than the time-resolution can be correctly monitored. -- Abstract: Utility and constraints on using the pump-probe photoelectron spectroscopy for detecting the time-resolved surface photovoltage on the semiconductor surface are discussed by solving the equation of motion for the electron from the sample to the analyzer. The escape time, which is defined as the time for the electron to achieve the 99% of the photovoltage, determines the basic temporal resolution. It can be derived from a simple formula with the pump beam radius and the initial kinetic energy of the electron and lies in a range of nano seconds with a usual experimental condition so far. However, an analysis revealed that a time constant for the decay in the SPV can be correctly measured with the decay in the kinetic-energy shift as a function of the pump-probe time difference even for a much shorter time constant than the escape time. Meanwhile, the value of the kinetic-energy shift does not agree with the true SPV. The relation between the true SPV and the observed kinetic-energy shift is estimated.

  12. Utility and constraint on the use of pump-probe photoelectron spectroscopy for detecting time-resolved surface photovoltage

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Shin-ichiro, E-mail: stanaka@sanken.osaka-u.ac.jp [The Institute of the Industrial and Scientific Research, Osaka University, 567-0047 Mihogaoka, Ibaraki, Osaka (Japan)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer The pump-probe PES method for detecting time-resolved surface photovoltage (SPV) is analyzed. Black-Right-Pointing-Pointer The simulation for the trip of the electron from the sample to the analyzer revealed its utility and constraint. Black-Right-Pointing-Pointer The basic time-resolution is determined by the pump-spot radius and the electron energy. Black-Right-Pointing-Pointer The lifetime of the SPV that is shorter than the time-resolution can be correctly monitored. -- Abstract: Utility and constraints on using the pump-probe photoelectron spectroscopy for detecting the time-resolved surface photovoltage on the semiconductor surface are discussed by solving the equation of motion for the electron from the sample to the analyzer. The escape time, which is defined as the time for the electron to achieve the 99% of the photovoltage, determines the basic temporal resolution. It can be derived from a simple formula with the pump beam radius and the initial kinetic energy of the electron and lies in a range of nano seconds with a usual experimental condition so far. However, an analysis revealed that a time constant for the decay in the SPV can be correctly measured with the decay in the kinetic-energy shift as a function of the pump-probe time difference even for a much shorter time constant than the escape time. Meanwhile, the value of the kinetic-energy shift does not agree with the true SPV. The relation between the true SPV and the observed kinetic-energy shift is estimated.

  13. 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.

  14. X-ray photoelectron spectroscopy analysis of aluminum and copper cleaning procedures for the Advanced Photon Source

    International Nuclear Information System (INIS)

    The Advanced Photon Source (APS), presently under construction, will produce x rays of unprecedented brightness. The storage ring where the x rays will be produced will be constructed from an extruded 6063 aluminum alloy, while transition pieces (flanges, etc.) will be made from a 2219 aluminum alloy. In addition, cooled photon absorbers will be placed in strategic locations throughout the ring to intercept the majority of the unused high power-density radiation. These will be made of either CDA-101 (OFHC) copper or glidcop (a dispersion strengthened copper alloy). Before any of these components can be assembled they must be cleaned to remove surface contaminants so that the ultrahigh vacuum (<0.1 nTorr) necessary for successful operation can be achieved. Many recipes for cleaning aluminum and copper exist; however, most of them involve the use of chemicals that present safety and/or environmental concerns. We have undertaken an x-ray photoelectron spectroscopy study of the effects of a variety of commercially available cleaners on the surface cleanliness of aluminum and copper. Several important results have been identified in this study. A simple alkaline detergent in an ultrasonic bath cleans aluminum alloys as effectively as the more aggressive cleaning solutions. The detergent can be used at 65 degree C to clean the 6063 alloy and at 50 degree C to clean the 2219 alloy. A citric acid based cleaner was found to be effective at cleaning copper, although the surface oxidizes rapidly. To date, we have been unable to find a universal cleaning procedure, i.e., one that is optimal for cleaning both Al and Cu

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

    International Nuclear Information System (INIS)

    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 (La2O3) 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 La2O3 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 La2O3 and La(OH)3. The information of oxygen species, O2- component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O2−), two chemisorb component (La2O3) and La(OH)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

  16. (3+1) Resonance enhanced multiphoton ionization-photoelectron spectroscopy on the E, F, and G Rydberg states of ClO

    OpenAIRE

    Buma, W.J.; Wales, N. P. L.; Lange

    1996-01-01

    (3 + 1) resonance enhanced multiphoton ionization-photoelectron spectroscopy is employed to investigate the spectroscopy and ionization dynamics of the E, F, and G Rydberg states of ClO. The results establish that the E and F Rydberg states converge upon the X3- ground ionic state, while the G state belongs to a Rydberg series with an excited a 1D ioni core. Improved ionization thresholds of these two ionic states are determined as 10.887 ± 0.005 and 11.750 ± 0.005 eV.

  17. Cation distribution in co-doped ZnAl2O4 nanoparticles studied by X-ray photoelectron spectroscopy and 27Al solid-state NMR spectroscopy.

    Science.gov (United States)

    Duan, Xiulan; Yuan, Duorong; Yu, Fapeng

    2011-06-20

    Co(x)Zn(1-x)Al(2)O(4) (x = 0.01-0.6) nanoparticles were synthesized by the citrate sol-gel method and were characterized by X-ray powder diffraction and transmission electron microscopy to identify the crystalline phase and determine the particle size. X-ray photoelectron spectroscopy and (27)Al solid-state NMR spectroscopy were used to study the distribution of the cations in the tetrahedral and octahedral sites in Co(x)Zn(1-x)Al(2)O(4) nanoparticles as a function of particle size and composition. The results show that all of the as-synthesized samples exhibit spinel-type single phase; the crystallite size of the samples is about 20-50 nm and increases with increasing annealing temperature and decreases with Co-enrichment. Zn(2+) ions are located in large proportions in the tetrahedral sites and in small proportions in the octahedral sites in Co(x)Zn(1-x)Al(2)O(4) nanoparticles. The fraction of octahedral Zn(2+) increases with increasing Co concentration and decreases with increasing particle size. Besides the tetrahedral and octahedral coordinations, the presence of the second octahedrally coordinated Al(3+) ions is observed in the nanoparticles. The change of the inversion parameter (2 times the fraction of Al(3+) ions in tetrahedral sites) with Co concentration and particle size is consistent with that of the Zn fraction in octahedral sites. Analysis of the absorption properties indicates that Co(2+) ions are located in the tetrahedral sites as well as in the octahedral sites in the nanoparticles. The inversion degree of Co(2+) decreases with increasing particle size. PMID:21612229

  18. Attosecond measurements without attosecond pulses: using particle correlation

    International Nuclear Information System (INIS)

    Full text: We describe how time and energy correlations between the electrons can be used to trace the dynamics of correlated two-electron ionization with sub-femtosecond precision, without using sub-femtosecond pulses. The approach is illustrated using the example of Auger or Coster-Kronig decay triggered by photo-ionization with an XUV pulse. It requires correlated measurements of angle-resolved energy spectra of both the photo- and Auger electrons in the presence of a laser pulse. Neither the XUV, nor the laser pulse have to be short compared to the decay time. We begin complete characterization of a process by reconstructing amplitude and phase of a correlated two-electron spectrum. Phase information is obtained in a manner similar to SPIDER reconstruction method of conventional ultrafast spectroscopy, where there is no fundamental limit to time resolution. Spectral phase is mapped onto amplitude modulation of spectral intensity by recording the interference of the original spectrum with its spectrally-shifted replica. Particle correlation also allows us to effectively solve the deconvolution problem, uncovering the fast component of the correlated process. One essential requirement, however, is temporal stability of the probe pulse relative to the pump: their relative jitter degrades time resolution. Fortunately, modem few-cycle infrared (IR) femtosecond pulses can be phase stabilized with incredible attosecond precision over very long times, naturally leading to attosecond stabilization of XUV pulses which they generate. Our approach can be used for any process resulting in the emission of two charged particles with fixed total energy. Examples are shake-off in one-photon two-electron ionization, photo-induced Auger or Coster-Kronig decay, etc. Ultrafast stages of such processes which can be time-resolved with our approach can also include Zeno and anti-Zeno stages of decay, core rearrangement, non-exponential decay due to structured continuum, etc. Ref. 1

  19. Synchrotron radiation photoelectron spectroscopy studies of self-organization in As.sub.40./sub.Se.sub.60./sub. nanolayers stored under ambient conditions and after laser irradiation

    Czech Academy of Sciences Publication Activity Database

    Kondrat, O.; Popovich, N.; Holomb, R.; Mitsa, V.; Lyamayev, V.; Tsud, N.; Cháb, Vladimír; Matolín, V.; Prince, K. C.

    2012-01-01

    Roč. 358, č. 21 (2012), s. 2910-2916. ISSN 0022-3093 Institutional support: RVO:68378271 Keywords : chalcogenide glass * photostructural changes * photoelectron spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.597, year: 2012

  20. 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.

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

    Science.gov (United States)

    Shokri, Alireza; Wang, Xue-Bin; Wang, Yanping; O'Doherty, George A; Kass, Steven R

    2016-03-17

    Flexible acyclic alcohols with one to five hydroxyl groups were bound to a 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 nonionic 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 tetrabutylammonium 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 molecular

  2. 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

  3. 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

  4. Theory of attosecond delays in laser-assisted photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Dahlström, J.M., E-mail: marcus.dahlstrom@fysik.su.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Atomic Physics, Fysikum, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Guénot, D.; Klünder, K.; Gisselbrecht, M.; Mauritsson, J. [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); L’Huillier, A., E-mail: anne.lhuillier@fysik.lth.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Maquet, A. [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France); Taïeb, R., E-mail: richard.taieb@upmc.fr [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France)

    2013-03-12

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself.

  5. Theory of attosecond delays in laser-assisted photoionization

    International Nuclear Information System (INIS)

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself

  6. X-Ray Two-Photon Photoelectron Spectroscopy: A Theoretical Study of Inner-Shell Spectra of the Organic Para-Aminophenol Molecule

    International Nuclear Information System (INIS)

    The inner-shell single and double ionization spectra of the organic molecule para-aminophenol are calculated using many-body Green's function methods. The inner-shell double ionization spectrum displays more pronounced sensitivity to the chemical environment and to electronic many-body effects than does the inner-shell single ionization spectrum. A kinetic model is employed to determine the probability of inner-shell double hole formation in para-aminophenol exposed to an intense, 1 fs x-ray pulse. The resulting photoelectron spectrum at a photon energy of 1 keV is calculated. This work suggests that x-ray two-photon photoelectron spectroscopy using x-ray free-electron lasers will provide access to electronic-structure information not currently available.

  7. 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. PMID:22852618

  8. Photoelectron spectroscopy of aqueous solutions: Streaming potentials of NaX (X = Cl, Br, and I) solutions and electron binding energies of liquid water and X−

    International Nuclear Information System (INIS)

    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

  9. Exploring intense attosecond pulses

    Science.gov (United States)

    Charalambidis, D.; Tzallas, P.; Benis, E. P.; Skantzakis, E.; Maravelias, G.; Nikolopoulos, L. A. A.; Peralta Conde, A.; Tsakiris, G. D.

    2008-02-01

    After introducing the importance of non-linear processes in the extreme-ultra-violet (XUV) spectral regime to the attosecond (asec) pulse metrology and time domain applications, we present two successfully implemented techniques with excellent prospects in generating intense asec pulse trains and isolated asec pulses, respectively. For the generation of pulse trains two-color harmonic generation is exploited. The interferometric polarization gating technique appropriate for the generation of intense isolated asec pulses is discussed and compared to other relevant approaches.

  10. Isolated attosecond soft X-rays and water window XAFS

    Science.gov (United States)

    Biegert, Jens

    2016-05-01

    We demonstrate generation of isolated attosecond soft X-ray pulses with duration less than 350 as at the carbon K-edge at 284 eV. This reproducible and CEP stable attosecond soft X-ray continuum covers the entire water window from 200 eV to 550 eV with a flux of 7.3x 107 photons/s and corresponds to a pulse energy of 2.9 pJ. We demonstrate the utility of our table-top source through soft X-ray near-edge fine-structure spectroscopy at K-shell absorption edges in condensed matter and retrieve the specific absorption features corresponding to the binding orbitals. We believe that these results herald attosecond material science by bridging the gap between ultrafast temporal resolution and element specific probing at the fundamental absorption edges of matter.

  11. Attosecond streaking in a nano-plasmonic field

    Science.gov (United States)

    Kelkensberg, F.; Koenderink, A. F.; Vrakking, M. J. J.

    2012-09-01

    A theoretical study of the application of attosecond streaking spectroscopy to time-resolved studies of the plasmonic fields surrounding isolated, resonantly excited spherical nanoparticles is presented. A classification of the different regimes in attosecond streaking is proposed and identified in our results that are derived from Mie calculations of plasmon fields, coupled to classical electron trajectory simulations. It is shown that in an attosecond streaking experiment, the electrons are almost exclusively sensitive to the component of the field parallel to the direction in which they are detected. This allows one to probe the different components of the field individually by resolving the angle of emission of the electrons. Finally, simulations based on fields calculated by finite-difference time-domain (FDTD) are compared with the results obtained using Mie fields. The two are found to be in good agreement with each other, supporting the notion that FDTD methods can be used to reliably investigate non-spherical structures.

  12. Photoelectron spectroscopy of sequential three-photon double ionization of Ar irradiated by EUV free-electron laser pulses

    International Nuclear Information System (INIS)

    We have investigated the ionization of the Ar atom by 51 nm extreme-ultraviolet light pulses at the free-electron laser facility, SPring-8 Compact SASE Source test accelerator, in Japan. The angle-resolved photoelectron spectra contain lines due to sequential three-photon double ionization with the second ionization step proceeding via the resonantly enhanced two-photon absorption. The relative intensities of the corresponding photoelectron peaks and their angular dependence are explained in the framework of a three-step model of the process. (fast track communication)

  13. Photoelectron spectroscopy of sequential three-photon double ionization of Ar irradiated by EUV free-electron laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Fukuzawa, H; Gryzlova, E V; Motomura, K; Yamada, A; Ueda, K; Piseri, P; Mazza, T; Devetta, M [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Grum-Grzhimailo, A N; Strakhova, S I [Institute of Nuclear Physics, Moscow State University, Moscow 119991 (Russian Federation); Nagaya, K; Sugishima, A; Mizoguchi, Y; Iwayama, H; Yao, M; Saito, N; Coreno, M; Nagasono, M; Tono, K; Yabashi, M, E-mail: fukuzawa@tagen.tohoku.ac.j [RIKEN, XFEL Project Head Office, Sayo, Hyogo 679-5148 (Japan)

    2010-06-14

    We have investigated the ionization of the Ar atom by 51 nm extreme-ultraviolet light pulses at the free-electron laser facility, SPring-8 Compact SASE Source test accelerator, in Japan. The angle-resolved photoelectron spectra contain lines due to sequential three-photon double ionization with the second ionization step proceeding via the resonantly enhanced two-photon absorption. The relative intensities of the corresponding photoelectron peaks and their angular dependence are explained in the framework of a three-step model of the process. (fast track communication)

  14. Electronic structure of single crystal UPd3, UGe2, and USb2 from hard X-ray and angle-resolved photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Highlights: → Electronic structure of single crystal UPd3, UGe2, and USb2 was measured by hard X-ray and angle-resolved photoemission spectroscopy. → Angle resolved photoemission results demonstrate hybridization between U 5f and Pd 4d electrons within UPd3. → HAXPES probing of bulk features within of UPd3, UGe2, and USb2 samples with native oxide contamination demonstrated. → Two distinct spectral features identified for Sb I and Sb II sites within USb2 HAXPES spectrum. → Line shape analysis reveals correlations between Doniach-Sunjic asymmetry coefficients and 5f localization. - Abstract: Electronic structure of single crystal UPd3, UGe2, and USb2 has been measured from hard X-ray photoelectron spectroscopy (HAXPES) with 7.6 keV photons at the European Synchrotron Radiation Facility (ESRF). Lower photon energy angle-resolved photoelectron spectroscopy (ARPES) was also performed at the Synchrotron Radiation Center (SRC). Herein the following results are presented: (i) ARPES results demonstrate hybridization between the U 5f and Pd 4d electrons within UPd3. (ii) The greatly reduced surface sensitivity of HAXPES enabled observation of the bulk core levels in spite of surface oxidation. Photoelectron mean-free-path versus oxide layer thickness considerations were used to model the effectiveness of HAXPES for probing bulk features of in-air cleaved samples. (iii) Two distinct features separated by 800 meV were observed for the Sb 3d core level. These two features are attributed to manifestations of two distinct Sb sites within the USb2 single crystal as supported by consideration of interatomic distances and enthalpy-of-formation. (iv) Doniach-Sunjic line shape analysis of core level spectral features revealed correlations between asymmetry coefficients and 5f localization.

  15. A photoelectron spectroscopy study of the electronic structure evolution in CuInSe{sub 2}-related compounds at changing copper content

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsova, T. V.; Grebennikov, V. I. [Institute of Metal Physics, UB RAS, 620041 Ekaterinburg (Russian Federation); Zhao, H. [Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Derks, C.; Taubitz, C.; Neumann, M. [University of Osnabrueck, D-49069 Osnabrueck (Germany); Persson, C. [Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Department of Physics, University of Oslo, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Kuznetsov, M. V. [Institute of Solid State Chemistry, UB RAS, 620990 Ekaterinburg (Russian Federation); Urals Federal University, 19 Mira Str., Ekaterinburg 620002 (Russian Federation); Bodnar, I. V. [Department of Chemistry, Belarusian State University of Informatics and Radioelectronics, P. Brovka 6, 220027 Minsk (Belarus); Martin, R. W.; Yakushev, M. V. [Department of Physics, SUPA, Strathclyde University, G4 0NG Glasgow (United Kingdom)

    2012-09-10

    Evolution of the valence-band structure at gradually increasing copper content has been analysed by x-ray photoelectron spectroscopy (XPS) in In{sub 2}Se{sub 3}, CuIn{sub 5}Se{sub 8}, CuIn{sub 3}Se{sub 5}, and CuInSe{sub 2} single crystals. A comparison of these spectra with calculated total and angular-momentum resolved density-of-states (DOS) revealed the main trends of this evolution. The formation of the theoretically predicted gap between the bonding and non-bonding states has been observed in both experimental XPS spectra and theoretical DOS.

  16. A photoelectron spectroscopy study of the electronic structure evolution in CuInSe2-related compounds at changing copper content

    International Nuclear Information System (INIS)

    Evolution of the valence-band structure at gradually increasing copper content has been analysed by x-ray photoelectron spectroscopy (XPS) in In2Se3, CuIn5Se8, CuIn3Se5, and CuInSe2 single crystals. A comparison of these spectra with calculated total and angular-momentum resolved density-of-states (DOS) revealed the main trends of this evolution. The formation of the theoretically predicted gap between the bonding and non-bonding states has been observed in both experimental XPS spectra and theoretical DOS.

  17. Study by X-ray photoelectron spectroscopy (XPS) and radiochemistry (Cl36) of the interaction of chloride ions with a passive film formed on nickel

    International Nuclear Information System (INIS)

    This research thesis reports the study of the influence of chlorides on nickel passivation by using a radiochemical method based on the use of the Cl36 isotope and the X-ray photoelectron spectroscopy (XPS). The first one allows the in-situ determination of the adsorption of chlorides on the surface, or their inclusion in surface films during the electrochemical treatment. The XPS analysis allows the characterization of modifications induced by chlorides in passive films. The obtained results allow a better understanding in the interpretation of the mechanisms of corrosion induced by chloride ions

  18. Zero kinetic energy-pulsed field ionization and resonance enhanced multiphoton ionization photoelectron spectroscopy: ionization dynamics of Rydberg states in HBr.

    OpenAIRE

    Wales, N.P.L.; Buma, W.J.; Lange; Lefebvre-Brion, H.; Wang, K.; McKoy, V.

    1996-01-01

    The results of rotationally resolved resonance enhanced multiphoton ionization photoelectron spectroscopy and zero kinetic energy‐pulsed field ionization studies on HBr via various rotational levels of the F^ 1Δ_2 and f^ 3Δ_2 Rydberg states are reported. These studies lead to an accurate determination of the lowest ionization threshold as 94 098.9±1 cm^(−1). Observed rotational and spin–orbit branching ratios are compared to the results of ab initio calculations. The differences between theor...

  19. A quantitative study of air-borne particulate matter collected on membrane filters by means of X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The capability of X-ray photoelectron spectroscopy, XPS or ESCA, in analysing oxidation states and measuring the concentration of elements present in air pollution particulates collected on membrane filters is evaluated. Semi-quantitative data are compared with those from XRF and wet chemical analysis. Differences of about a factor of 2.0-2.5 are found which are critically discussed in relation to particle size and the distribution of ionic species. The importance of intrinsic properties of matrix materials and instrumental factors is also discussed. (orig.)

  20. X-ray photoelectron spectroscopy analysis for undegraded and degraded Gd2O2S:Tb3+ phosphor thin films

    International Nuclear Information System (INIS)

    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.

  1. Valence band offset of β-Ga2O3/wurtzite GaN heterostructure measured by X-ray photoelectron spectroscopy

    OpenAIRE

    Wei, Wei; Qin, Zhixin; Fan, Shunfei; Li, Zhiwei; Shi, Kai; Zhu, Qinsheng; Zhang, Guoyi

    2012-01-01

    A sample of the β-Ga2O3/wurtzite GaN heterostructure has been grown by dry thermal oxidation of GaN on a sapphire substrate. X-ray diffraction measurements show that the β-Ga2O3 layer was formed epitaxially on GaN. The valence band offset of the β-Ga2O3/wurtzite GaN heterostructure is measured by X-ray photoelectron spectroscopy. It is demonstrated that the valence band of the β-Ga2O3/GaN structure is 1.40 ± 0.08 eV.

  2. Utilization of the statistics techniques for the analysis of the XPS (X-ray photoelectron spectroscopy) and Auger electronic spectra's deconvolutions

    International Nuclear Information System (INIS)

    For the analysis of the XPS (X-ray photoelectron spectroscopy) and Auger spectra, it is important to performe the peaks' separation and estimate its intensity. For this purpose, a methodology was implemented, including: a spectrum's filter; b) substraction of the base line (or inelastic background); c) deconvolution (separation of the distribution that integrates the spectrum) and d) error of calculation of the mean estimation, comprising adjustment quality tests. A software (FORTRAN IV plus) that permits to use the methodology proposed from the experimental spectra was implemented. The quality of the methodology was tested with simulated spectra. (Author)

  3. High-resolution soft-X-ray beamline ADRESS at Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

    OpenAIRE

    Strocov, V. N.; Schmitt, T; U. Flechsig; Schmidt, T.; Imhof, A; Q. Chen; J. Raabe; Betemps, R.; Zimoch, D.; Krempasky, J.; A. Piazzalunga; X Wang; Grioni, M.; Patthey, L.

    2009-01-01

    We describe the concepts and technical realization 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). 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 deg rotatable linear polarizations) but als...

  4. High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

    OpenAIRE

    Strocov, V. N.; Schmitt, T; U. Flechsig; Schmidt, T.; Imhof, A; Q. Chen; J. Raabe; Betemps, R.; Zimoch, D.; Krempasky, J.; X Wang; Grioni, M.; A. Piazzalunga; Patthey, L.

    2010-01-01

    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...

  5. Photoelectron Spectroscopy and Electronic Structure Calculations of d1 Vanadocene Compounds with Chelated Dithiolate Ligands: Implications for Pyranopterin Mo/W Enzymes

    OpenAIRE

    Cranswick, Matthew A.; Dawson, Alice; Cooney, J. Jon A.; Gruhn, Nadine E.; Lichtenberger, Dennis L.; Enemark, John H.

    2007-01-01

    Gas-phase photoelectron spectroscopy and density functional theory have been used to investigate the electronic structures of open-shell bent vanadocene compounds with chelating dithiolate ligands, which are minimum molecular models of the active sites of pyranopterin Mo/W enzymes. The compounds Cp2V(dithiolate) [where dithiolate is 1,2-ethenedithiolate (S2C2H2) or 1,2-benzenedithiolate (bdt), and Cp is cyclopentadienyl] provide access to a 17-electron, d1 electron configuration at the metal ...

  6. 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.

  7. X-ray photoelectron spectroscopy investigation of the Schottky barrier at low-k a-SiO(C):H/Cu interfaces

    International Nuclear Information System (INIS)

    In order to understand the fundamental mechanisms involved in electrical leakage in low-k/Cu interconnects, we have utilized x-ray photoelectron spectroscopy to determine the Schottky barrier present at interfaces formed by plasma enhanced chemical vapor deposition of low-k a-SiOxCy:H thin films on polished Cu substrates. We find the Schottky Barrier at this interface to range widely from 1 to >4 eV and to be dependent on the amount of network carbon incorporated into the a-SiOC:H thin films.

  8. X-ray photoelectron spectroscopy investigations of Y{sub 3}Al{sub 5}O{sub 12}:Yb single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kruczek, M.; Sakowska, H.; Gala, M.; Swirkowicz, M. [Institute of Electronic Materials Technology, 133 Wolczynska Str., 01-919 Warsaw (Poland); Talik, E. [Institute of Physics, University of Silesia, 4 Uniwersytecka Str., 40-007 Katowice (Poland)

    2005-04-01

    X-ray photoelectron spectroscopy was used to study the chemical composition and electronic structure of the Y{sub 3}Al{sub 5}O{sub 12}:Yb (YAG:Yb) crystals. The contamination of the crystal with carbon and oxygen in the broken under UHV sample was found. The dopant concentration of Yb, in the mixed valence state, was determined as 12 %. The aluminium concentration is lower than a nominal value. The chemical shift analysis shows more ionic bond of Y-O than Al-O. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Dynamic secondary ion mass spectrometry and X-ray photoelectron spectroscopy on artistic bronze and copper artificial patinas

    International Nuclear Information System (INIS)

    To prevent the natural processes of decay and to develop and improve the treatments of conservation and restoration of artistic bronzes meaning statues and sculptures, it is important understanding the patination processes and the knowledge of artificially corroded surfaces. Chemical and physical characterization of artificial patinas obtained on artistic bronzes and coppers by using the 19th century Western traditional patination techniques and recipes by means of SEM-EDS, light microscopy and ATR/FT-IR has been done in previous studies [I.Z. Balta, L. Robbiola, Characterization of artificial black patinas on artistic cast bronze and pure copper by using SEM-EDS and light microscopy, in: Proceedings of the 13th European Microscopy Congress, 22-27 August 2004, Antwerp, Belgium, EMC 2004 CD-Rom Conference Preprints; I.Z. Balta, L. Robbiola, Traditional artificial artistic bronze and copper patinas-an investigation by SEM-EDS and ATR/FT-IR, in: Proceedings of the 8th International Conference on Non Destructive Investigations and Microanalysis for the Diagnostics and Conservation of the Cultural and Environmental Heritage, 15-19 May 2005, Lecce, Italy, ART'05 CD-Rom Conference Preprints]. Differences in morphology (structure, thickness, porosity, adherence, compactity, uniformity, homogeneity) and also in composition, on both artistic cast bronze and pure copper patinas, were clearly evidenced. Further in-depth investigation is required to be carried out in order to better understand the patinas mechanisms of formation and the layers kinetics of growth. The elemental and chemical analysis, either on a surface monolayer or in a depth profile, by using the Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS) techniques, can provide this kind of information, unique at trace-level sensitivity. SIMS has proved to be a suitable analytical technique for analyzing small amounts of material with high atomic sensitivity (ppm or even ppb) and high

  10. Design and development of a high energy photo-electron spectroscopy beamline on Indus-2 synchrotron radiation source

    International Nuclear Information System (INIS)

    We report on the design and development of a high energy x-ray photo-electron spectroscopy (XPS) beamline for one of the bending magnets (BM-6) at the 2.5 GeV, 3 rd generation Indus-2 synchrotron radiation (SR) source under commissioning at the Raja Ramanna Centre for Advanced Technology, Indore. The beamline (BL) extends up to 40 m in length, and has been designed based on certain criteria such as its working energy range (0.8 - 15.0 keV), the resolution (∼ 10-4), the flux throughput (1010-1011), and the requirement of a focused beam at the sample position. Two pairs of identical crystals in the (+1, -1) double crystal monochromator (DCM) geometry, based on beryl (10i0) and Si (111) reflections with their intrinsic resolution of ∼ 10-4 have been chosen to respectively cover the lower (0.8-2.0 keV) and higher energy (2 - 15.0 keV) ranges of the BL. The DCM has been placed at a distance of 30.0 m from the BM source. The effect of pitch (ΔΘP) and roll errors (ΔΘR) of the DCM on the vertical and horizontal shifts in the exit beam has been evaluated and minimized to acceptable values (ΔΘP R < 2 μrad) that correspond to shifts of less than 20 % of the beam width at the sample position. Sagittal focusing has been achieved by bending the 2 nd Si crystal of the DCM in the sagittal direction. A mirror has been placed at 20.0 m from the BM source. The toroidal surface of the mirror substrate (1.2 m long Si crystal) is coated with a thin film of Pt metal (∼ 50 nm), and held at a grazing angle of 9.0 μrad so that it provides high reflectivity in a much wider energy range from 0.8 to 8.0 keV. The effect of mirror surface imperfections, such as the roughness and figure error, on the spot size at its focal position has been evaluated and optimized using a ray-trace program SHADOW. The optimum value for the roughness is found to be 3.0 A, while those for figure errors are found to be 2.0 and 20.0 μrad in the meridional and sagittal directions, respectively. Further

  11. Dynamic secondary ion mass spectrometry and X-ray photoelectron spectroscopy on artistic bronze and copper artificial patinas

    Science.gov (United States)

    Balta, I. Z.; Pederzoli, S.; Iacob, E.; Bersani, M.

    2009-04-01

    To prevent the natural processes of decay and to develop and improve the treatments of conservation and restoration of artistic bronzes meaning statues and sculptures, it is important understanding the patination processes and the knowledge of artificially corroded surfaces. Chemical and physical characterization of artificial patinas obtained on artistic bronzes and coppers by using the 19th century Western traditional patination techniques and recipes by means of SEM-EDS, light microscopy and ATR/FT-IR has been done in previous studies [I.Z. Balta, L. Robbiola, Characterization of artificial black patinas on artistic cast bronze and pure copper by using SEM-EDS and light microscopy, in: Proceedings of the 13th European Microscopy Congress, 22-27 August 2004, Antwerp, Belgium, EMC 2004 CD-Rom Conference Preprints; I.Z. Balta, L. Robbiola, Traditional artificial artistic bronze and copper patinas—an investigation by SEM-EDS and ATR/FT-IR, in: Proceedings of the 8th International Conference on Non Destructive Investigations and Microanalysis for the Diagnostics and Conservation of the Cultural and Environmental Heritage, 15-19 May 2005, Lecce, Italy, ART'05 CD-Rom Conference Preprints]. Differences in morphology (structure, thickness, porosity, adherence, compactity, uniformity, homogeneity) and also in composition, on both artistic cast bronze and pure copper patinas, were clearly evidenced. Further in-depth investigation is required to be carried out in order to better understand the patinas mechanisms of formation and the layers kinetics of growth. The elemental and chemical analysis, either on a surface monolayer or in a depth profile, by using the Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS) techniques, can provide this kind of information, unique at trace-level sensitivity. SIMS has proved to be a suitable analytical technique for analyzing small amounts of material with high atomic sensitivity (ppm or even ppb) and high

  12. 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.

  13. Angle-resolved photoelectron spectroscopy of Cl2 as a function of photon energy from 18 to 70 eV

    International Nuclear Information System (INIS)

    Angle-resolved photoelectron spectroscopy using synchrotron radiation has been carried out on gaseous chlorine as a function of photon energy from 18 to 70 eV. From this data the partial cross sections and angular distribution parameter ν have been derived for the first three orbitals. For the lone pair orbitals 2π/sub g/ and 2π/sub u/, distinct minima are found in both the partial cross sections and ν values in the region of photoelectron energies from 30 to 40 eV. Less well-defined minima are also seen in the case photoionization for the nonlone pair orbital 5sigma/sub g/. These features are believed related to the Cooper minimum that arises from an atomic 3p subshell. Calculations have also been carried out on the partial cross sections and ν values using the multiple scattering Xα method. Comparison with experiment gives excellent qualitative agreement with regard to the ''Cooper minimum.'' The nature of the Cooper minimum in molecules and its usefulness in understanding photoelectron dynamics is discussed

  14. 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.

  15. Autler-Townes effects in attosecond circular polarization molecular photoionization

    International Nuclear Information System (INIS)

    We present molecular photoionization simulations by intense (I ∼ 1016 W/cm2) few cycle circularly polarized attosecond extreme ultraviolet laser pulses for aligned H2+ from numerical solutions of the corresponding time-dependent Schrodinger equation. With appropriate laser pulse parameters, circular attosecond coherent electron wave packets (CEWPs) are created in excited Rydberg states. Such CEWPs are spatially localized during ionization processes, thus resulting in sufficient population oscillations between the resonant excited Rydberg states and the initial ground state. Consequently Autler-Townes splitting in circular polarization energy spectra is predicted, which is shown to be critically sensitive to the pulse intensity, duration, and polarization. The resulting photoelectron angular distributions are rotated with respect to the molecular axis due to the nonspherical Coulomb potential of the molecule, resulting in different ionization rates at different laser polarization-molecular angles.

  16. Attosecond Streaking in the Low-Energy Region

    International Nuclear Information System (INIS)

    The low-energy photonelectron (PEs) ionized by a single attosecond pulse can be controlled by a moderately intense infrared field (IR). The electric field of the IR pulse can drive part of the PEs back to the parent ion and induce multiple rescattering of the electrons. Interesting interference patterns are observed in the photoelectron momentum distributions, which are formed by the rescattered electrons and the directly ionized PEs. By analyzing the interference patterns with a simple semiclassical model, which considers the particular PE trajectories incorporating the rescattering with the core, we demonstrate that the low-energy attosecond streaking offers a promising method of holographic imaging of atomic and molecular potential. In addition, we show that neither strong field approximation (SFA) or Coulomb-Volkov approximation (CVA) is able to reproduce these interesting structures at the low energy region

  17. Catalyst Chemical State during CO Oxidation Reaction on Cu(111) Studied with Ambient-Pressure X-ray Photoelectron Spectroscopy and Near Edge X-ray Adsorption Fine Structure Spectroscopy.

    Science.gov (United States)

    Eren, Baran; Heine, Christian; Bluhm, Hendrik; Somorjai, Gabor A; Salmeron, Miquel

    2015-09-01

    The chemical structure of a Cu(111) model catalyst during the CO oxidation reaction in the CO+O2 pressure range of 10-300 mTorr at 298-413 K was studied in situ using surface sensitive X-ray photoelectron and adsorption spectroscopy techniques [X-ray photoelectron spectroscopy (XPS) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS)]. For O2:CO partial pressure ratios below 1:3, the surface is covered by chemisorbed O and by a thin (∼1 nm) Cu2O layer, which covers completely the surface for ratios above 1:3 between 333 and 413 K. The Cu2O film increases in thickness and exceeds the escape depth (∼3-4 nm) of the XPS and NEXAFS photoelectrons used for analysis at 413 K. No CuO formation was detected under the reaction conditions used in this work. The main reaction intermediate was found to be CO2(δ-), with a coverage that correlates with the amount of Cu2O, suggesting that this phase is the most active for CO oxidation. PMID:26275662

  18. Insights into the Photoelectron Spectroscopy of Chlorofluoroethenes Studied by Density-Functional and Coupled-Cluster Theories.

    Science.gov (United States)

    Huang, Cyong-Huei; Chou, Shang-Yi; Jang, Shiu-Bau; Lin, Yu-Chieh; Li, Chien-En; Chen, Chiing-Chang; Chang, Jia-Lin

    2016-03-01

    The first two ionic states of chlorofluoroethenes were studied by using both time-independent and time-dependent density-functional theories. We calculated the equilibrium geometries and harmonic vibrational frequencies of 1,1-, cis-, and trans-C2H2FCl and their cations by using the B3LYP and B3PW91 functionals together with the cc-pVTZ and aug-cc-pVTZ basis sets. Franck-Condon factors were computed by the method developed in our group, in which the Duschinsky effect was treated explicitly. A new technique, named alignment transformation, followed by Euler transformations was developed to achieve the Eckart conditions. The adiabatic ionization energies were calculated by the CCSD(T) method extrapolated to the complete basis set limit. Insights into the simulated photoelectron spectra of C2H2FCl indicate that the resolutions of recent threshold photoelectron experiments are not high enough to detect individual transitions. The high-resolution photoelectron spectra of C2H2FCl are predicted for future reference. The computed adiabatic ionization energies of the three isomers of C2H2FCl are in accord with the experiments with the absolute deviations ranging from 0.004 to 0.021 eV. We suggest that the agreement between experimental and theoretical spectra should be a key criterion to judge whether a spectral assignment is reasonable. PMID:26884146

  19. Confirmation of intrinsic electron gap states at nonpolar GaN(1-100) surfaces combining photoelectron and surface optical spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Himmerlich, M., E-mail: marcel.himmerlich@tu-ilmenau.de; Eisenhardt, A.; Shokhovets, S.; Krischok, S. [Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, 98684 Ilmenau (Germany); Räthel, J.; Speiser, E.; Neumann, M. D.; Navarro-Quezada, A.; Esser, N. [Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Strasse 9, 12489 Berlin (Germany)

    2014-04-28

    The electronic structure of GaN(1–100) surfaces is investigated in-situ by photoelectron spectroscopy (PES) and reflection anisotropy spectroscopy (RAS). Occupied surface states 3.1 eV below the Fermi energy are observed by PES, accompanied by surface optical transitions found in RAS around 3.3 eV, i.e., below the bulk band gap. These results indicate that the GaN(1–100) surface band gap is smaller than the bulk one due to the existence of intra-gap states, in agreement with density functional theory calculations. Furthermore, the experiments demonstrate that RAS can be applied for optical surface studies of anisotropic crystals.

  20. Hard X-ray photoelectron spectroscopy (HAXPES) (15 keV) at SpLine, the Spanish CRG beamline at the ESRF

    International Nuclear Information System (INIS)

    In this contribution we present the actual status of the SpLine project devoted to the implementation of hard (15 keV) X-ray photoelectron spectroscopy (HAXPES) in combination with surface X-ray diffraction (SXRD) at the Spanish CRG beamline (SpLine) at the European Synchrotron Radiation Facility (ESRF). The beamline is located at the bending magnet D25 at the ESRF and can be operated in the X-ray energy range 5-45 keV. The main project goals are the detection of very high kinetic energy photoelectrons up to 15 keV, in particular the simultaneous detection of the diffracted photons and photo-emitted electrons. Therefore, special effort has been devoted to develop a novel electron analyzer, capable of working at very high as well as low energies. The analyzer is a sector of a Cylindrical Mirror Analyzer (CSA300HV) with a five-elements retarding-lens system and a very compact size compared to standard hemispherical analyzers. Additionally, an ultra-high-vacuum system has been constructed which will simultaneously fulfill the requirements for HAXPES and SXRD. The vacuum chamber has two Be windows so that the in-coming and out-going X-ray beam will hit the sample and the X-ray detector, respectively. The complete system will be installed on a massive 2S+3D diffractometer. Photoelectron spectroscopy and SXRD can be operated either simultaneously or independently from each other. Test experiments with a UV discharge lamp and a RHEED electron gun have been conducted demonstrating that the analyzer performs satisfactorily. The whole set-up is in the commissioning phase and full operation is expected in the course of 2005

  1. Adsorption and deposition of anthraquinone-2-carboxylic acid on alumina studied by inelastic electron tunneling spectroscopy, infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Higo, Morihide [Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065 (Japan)], E-mail: higo@apc.kagoshima-u.ac.jp; Miake, Takeshi; Mitsushio, Masaru; Yoshidome, Toshifumi [Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065 (Japan); Ozono, Yoshihisa [Center for Instrumental analysis, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065 (Japan)

    2008-04-30

    The adsorption state of anthraquinone-2-carboxylic acid (AQ-2-COOH) deposited from acetone solutions (0.01-1.00 mg/ml) on native oxide surfaces of Al films was characterized by inelastic electron tunneling spectroscopy, infrared reflection absorption spectroscopy, and X-ray photoelectron spectroscopy. The oxide was prepared on evaporated Al films at room temperature in an oxygen-dc glow discharge. The morphology of the deposited AQ-2-COOH on the oxide surfaces was observed and analyzed by atomic force microscopy. These surface analyses showed that AQ-2-COOH is adsorbed predominantly as a uniform nanometer-scale film of carboxylate anions on the oxide surfaces deposited from solutions with concentrations lower than or equal to 0.02 mg/ml. It was found that AQ-2-COOH is adsorbed as both a uniform film of anions and as micron-sized particles of neutral molecules with heights of a few tens of nanometers when AQ-2-COOH is deposited from solutions with concentrations higher than 0.02 mg/ml. A comparison of the results obtained by these surface analytical techniques clearly shows the features and advantages of these analytical techniques.

  2. Self-compensation in ZnO thin films: An insight from X-ray photoelectron spectroscopy, Raman spectroscopy and time-of-flight secondary ion mass spectroscopy analyses

    International Nuclear Information System (INIS)

    As-grown ZnO typically exhibits n-type conductivity and the difficulty of synthesizing p-type ZnO for the realization of ZnO-based optoelectronic devices is mainly due to the compensation effect of a large background n-type carrier concentration. The cause of this self-compensation effect has not been conclusively identified although oxygen vacancies, zinc interstitials and hydrogen have been suggested. In this work, typical n-type ZnO thin films were prepared by sputtering and investigated using X-ray photoelectron spectroscopy, Raman spectroscopy and time-of-flight secondary ion mass spectroscopy to gain an insight on the possible cause of the self-compensation effect. The analyses found that the native defect that most likely behaved as the donor was zinc interstitial but some contribution of n-type conductivity could also come from the electronegative carbonates or hydrogen carbonates incorporated in the ZnO thin films

  3. Adsorption and deposition of anthraquinone-2-carboxylic acid on alumina studied by inelastic electron tunneling spectroscopy, infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy

    International Nuclear Information System (INIS)

    The adsorption state of anthraquinone-2-carboxylic acid (AQ-2-COOH) deposited from acetone solutions (0.01-1.00 mg/ml) on native oxide surfaces of Al films was characterized by inelastic electron tunneling spectroscopy, infrared reflection absorption spectroscopy, and X-ray photoelectron spectroscopy. The oxide was prepared on evaporated Al films at room temperature in an oxygen-dc glow discharge. The morphology of the deposited AQ-2-COOH on the oxide surfaces was observed and analyzed by atomic force microscopy. These surface analyses showed that AQ-2-COOH is adsorbed predominantly as a uniform nanometer-scale film of carboxylate anions on the oxide surfaces deposited from solutions with concentrations lower than or equal to 0.02 mg/ml. It was found that AQ-2-COOH is adsorbed as both a uniform film of anions and as micron-sized particles of neutral molecules with heights of a few tens of nanometers when AQ-2-COOH is deposited from solutions with concentrations higher than 0.02 mg/ml. A comparison of the results obtained by these surface analytical techniques clearly shows the features and advantages of these analytical techniques

  4. In situ study of an oxidation reaction on a Pt/C electrode by ambient pressure hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takagi, Yasumasa, E-mail: ytakagi@ims.ac.jp; Uemura, Yohei; Yokoyama, Toshihiko [Department of Molecular Structure, Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585 (Japan); The Graduate University for Advanced Studies (SOKENDAI), Myodaiji-cho, Okazaki, Aichi 444-8585 (Japan); Wang, Heng [Department of Molecular Structure, Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585 (Japan); Ikenaga, Eiji; Ohashi, Haruhiko; Senba, Yasunori; Yumoto, Hirokatsu; Yamazaki, Hiroshi; Goto, Shunji [Japan Synchrotron Radiation Research Institute, SPring-8, Koto, Sayo, Hyogo 679-5198 (Japan); Sekizawa, Oki; Iwasawa, Yasuhiro [Innovation Research Center for Fuel Cells, The University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Uruga, Tomoya [Japan Synchrotron Radiation Research Institute, SPring-8, Koto, Sayo, Hyogo 679-5198 (Japan); Innovation Research Center for Fuel Cells, The University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Tada, Mizuki [Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)

    2014-09-29

    We have constructed an ambient pressure X-ray photoelectron spectroscopy instrument that uses hard X-ray radiation at the high-performance undulator beamline BL36XU of SPring-8. The dependence of the Au 4f peak intensity from Au foil on the ambient N{sub 2} pressure was measured. At a photon energy of 7.94 keV, the Au 4f peak intensity maintained 40% at 3000 Pa compared with that at high vacuum. We designed a polymer electrolyte fuel cell that allows us to perform X-ray photoelectron spectroscopy measurements of an electrode under working conditions. The oxidized Pt peaks were observed in the Pt 3d{sub 5/2} level of Pt nanoparticles in the cathode, and the peaks clearly depended on the applied voltage between the anode and cathode. Our apparatus can be applied as a valuable in situ tool for the investigation of the electronic states and adsorbed species of polymer electrolyte fuel cell electrode catalysts under the reaction conditions.

  5. Molar concentration-depth profiles at the solution surface of a cationic surfactant reconstructed with angle resolved X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    In the current work, we first reconstructed the molar fraction-depth profiles of cation and anion near the surface of tetrabutylammonium iodide dissolved in formamide by a refined calculation procedure, based on angle resolved X-ray photoelectron spectroscopy experiments. In this calculation procedure, both the transmission functions of the core levels and the inelastic mean free paths of the photoelectrons have been taken into account. We have evaluated the partial molar volumes of surfactant and solvent by the densities of such solutions with different bulk concentrations. With those partial molar volumes, the molar concentration-depth profiles of tetrabutylammonium ion and iodide ion were determined. The surface excesses of both surfactant ions were then achieved directly by integrating these depth profiles. The anionic molar concentration-depth profiles and surface excesses have been compared with their counterparts determined by neutral impact ion scattering spectroscopy. The comparisons exhibit good agreements. Being capable of determining molar concentration-depth profiles of surfactant ions by core levels with different kinetic energies may extend the applicable range of ARXPS in investigating solution surfaces.

  6. Photoelectron spectroscopy of LiV2O4 with photons from 8.4 to 8100 eV. Bulk sensitivity, hybridization, and recoil effects

    International Nuclear Information System (INIS)

    Hard- and soft-X-ray photoelectron spectroscopies (HAXPES and SXPES) are very powerful for studying the bulk electronic structures of strongly correlated electron systems. The presence of an intrinsic surface layer on clean fractured surfaces is demonstrated for LiV2O4. In this material, single-nucleus recoil effects are very prominent not only for all core levels but also for valence states at 20 K. However, such recoil effects are negligible in VO2 even at 350 K in spite of the fact that VO2 has a similar V-O6 octahedron structure. The marked intensity increase in the high-binding-energy part of the so-called O 2p band relative to the V 3d band in HAXPES is interpreted to be due to the V 4s state contribution. Very high resolution extremely low energy photoelectron spectroscopy (ELEPES) is performed with Kr and Xe lamps at 10.1 and 8.4 eV, respectively, demonstrating its bulk sensitivity for this material with heavy-Fermion-like behavior. (author)

  7. Depth profiling the solid electrolyte interphase on lithium titanate (Li4Ti5O12) using synchrotron-based photoelectron spectroscopy

    DEFF Research Database (Denmark)

    Nordh, Tim; Younesi, Reza; Brandell, Daniel;

    2015-01-01

    The presence of a surface layer on lithium titanate (Li4Ti5O12, LTO) anodes, which has been a topic of debate in scientific literature, is here investigated with tunable high surface sensitive synchrotron-based photoelectron spectroscopy (PES) to obtain a reliable depth profile of the interphase....... electrode as such, and an electrode soaked in the electrolyte were analyzed by varying the photon energies enabling depth profiling of the outermost surface layer. The main components of the surface layer were found to be ethers, P-O containing compounds, and lithium fluoride.......The presence of a surface layer on lithium titanate (Li4Ti5O12, LTO) anodes, which has been a topic of debate in scientific literature, is here investigated with tunable high surface sensitive synchrotron-based photoelectron spectroscopy (PES) to obtain a reliable depth profile of the interphase....... Li||LTO cells with electrolytes consisting of 1 M lithium hexafluorophosphate dissolved in ethylene carbonate:diethyl carbonate (LiPF6 in EC:DEC) were cycled in two different voltage windows of 1.0-2.0 V and 1.4-2.0 V. LTO electrodes were characterized after 5 and 100 cycles. Also the pristine...

  8. Asymmetries in production of He+(n=2) with an intense few-cycle attosecond pulse

    Science.gov (United States)

    Djiokap, J. M. Ngoko; Hu, S. X.; Jiang, Wei-Chao; Peng, Liang-You; Starace, Anthony F.

    2013-07-01

    By solving the two-electron time-dependent Schrödinger equation, we study carrier-envelope-phase (CEP) effects on ionization plus excitation of He to He+(n=2) states by a few-cycle attosecond pulse with a carrier frequency of 51 eV. For most CEPs the asymmetries in the photoelectron angular distributions with excitation of He+(2s) or He+(2p) have opposite signs and are two orders of magnitude larger than for ionization without excitation. These results indicate that attosecond pulse CEP effects may be significantly amplified in correlated two-electron ionization processes.

  9. Effect of the carrier-envelope phase of the driving laser field on the high-order harmonic attosecond pulse

    International Nuclear Information System (INIS)

    The effect of the carrier-envelope phase of a few-cycle driving laser field on the generation and measurement of high-order harmonic attosecond pulses is investigated theoretically. We find that the position of the generated attosecond soft-x-ray pulse in the cutoff region is locked to the oscillation of the driving laser field, but not to the envelope of the laser pulse. This property ensures the success of the width measurement of an attosecond soft-x-ray pulse based on the cross correlation between the attosecond pulse and its driving laser pulse [M. Hentschel et al., Nature (London) 414, 509 (2001)]. However, there still exists a timing jitter of the order of tens of attoseconds between the attosecond pulse and its driving laser field. We also propose a method to detect the carrier-envelope phase of the driving laser field by measuring the spatial distribution of the photoelectrons induced by the attosecond soft-x-ray pulse and its driving laser pulse

  10. Relativistic attosecond physics

    International Nuclear Information System (INIS)

    Full text: Few-cycle laser pulses focused to a λ3 volume can produce relativistic intensities with only millijoules of energy. Relativistic intensity is achieved when the dimensionless field strength a0 ≥ 1, where a0 = eE0/meωc (for λ = 800 nm, a0 = 1 corresponds to I = 2x1018 W/cm2). In the relativistic λ3 regime, isolated attosecond pulses are efficiently formed through relativistic reflection, deflection, and compression. Particle-in-cell (PIC) simulations show that attosecond pulses are formed for a variety of plasma profiles, and the compressed pulse durations can scale inversely with driving field strength. The extreme spatial and temporal gradients achieved through λ3 focusing provides the strongest slopes in the plasma density, deflecting subsequent half-cycles of the driving radiation into unique non-specular directions. The same coherent motion of the critical surface that provides relativistic deflection also provides relativistic Doppler compression, generating attosecond pulses with conversion efficiency ∼ 10-1 under optimal conditions. Previously, isolated attosecond pulses have been generated using high harmonic generation in gases with conversion efficiency ∼ 10-6. Simulations indicate that the dense relativistic electron sheets can be extracted when the driving laser is incident on a sharp plasma boundary at large angles of incidence. Electrons are ejected from the plasma at locations of minimal pressure and are accelerated by the electromagnetic field. In turn, these electrons deflect and compress the radiation into a train of attosecond electromagnetic pulses. The electron bunches inherit a chirped energy structure with sub-cycle duration; -2x108 electrons per bunch are observed for specific simulation parameters. Relativistic deflection and compression is expected whenever relativistic intensity laser pulses interact with a critically dense plasma. For τ 30 fs laser pulses, we observe relativistic deflection and spectral broadening

  11. A study of a number of mixed transition metal oxide spinels using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    X-ray photoelectron spectra have been recorded from 5 series of characterised iron-chromium containing spinels. MnFex Cr2-xO4, Mn1-xFex Cr2O4, FexCr3-xO4, CoFex Cr2-xO4 and NiFex Cr2-xO4. Manganese 2p3/2 peak binding energies in the range of 640.0 to 641.3 eV were recorded from samples taken from both series of manganese spinels. Significant changes were noted in the nickel 2p photoelectron spectra and attributed to the displacement of the nickel (II) cation from octahedral to tetrahedral lattice positions. These changes included large shifts in the Ni 2p3/2 peak binding energy plus intensity and positional changes in the asssociated satellite structure. Shifts were also observed in the chromium 2p spectra which were related to the variation in sample composition. These shifts followed two distinct trends. Quantitative XPS analysis identified the surface segregation of chromium ions during the preparation of cobalt spinels and the segregation of both iron and chromium in the nickel containing compounds. (author)

  12. 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

  13. High-resolution threshold photoelectron and photoion spectroscopy of molecular nitrogen in the 15.0–52.7 eV photon energy range

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • High-resolution threshold photoelectron spectrum of N2 over the photon energy range 15.0–52.7 eV. • High-resolution photoion spectrum of N2 over the photon energy range 15.0–28.0 eV. • Spectroscopic constants for electronic states of N2+ from analyses of vibrational data. • Vibrational assignment of electronic states of N2+. • Rydberg state assignment for series converging on N2+ states. - Abstract: We have performed an extensive study of the threshold photoelectron spectrum of N2 over the valence ionization region 15.0–28.0 eV under high-resolution conditions. In addition, we measured the high-resolution photoion spectrum of N2 over the same photon energy range. These complimentary views of ionization in molecular systems provide different perspectives of the mechanism for the production of both ions and threshold electrons. The studies are presented in the context of our current understanding of the relationship between: (i) the autoionization of neutral Rydberg states and direct photoionization to (ii) the production of electrons and the ionic states of nitrogen at threshold. In both cases (ions and threshold electrons) we have found a considerable amount of new information on the vibrational states of a number of neutral and ionic electronic states. The inner valence ionization region of nitrogen was also investigated using threshold photoelectron spectroscopy over the photon energy range (27.7–52.7 eV) and is presented from the perspective of the formation of mixed-configuration ionic satellite states and the possibility of the involvement of ionic Rydberg states converging on the double ionization of nitrogen

  14. Molecular attosecond photoionization with few cycle XUV laser pulses

    International Nuclear Information System (INIS)

    We present molecular attosecond ionization with few cycle XUV laser pulses from numerical solutions of time dependent Schrodinger equations. Simulations performed on aligned H+2 exhibit signature of red-shifts in photoelectron energy spectra. This is shown to be critically sensitive to the the pulse duration and wavelength and is attributed to the broad spectral width of the ionizing pulses and diminishing electronic Franck-Condon factors with short pulses. We analyze the laser parameter dependence of the energy spectra by a perturbative model.

  15. 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.

  16. 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.

  17. Core-valence coupling in the Ru 4p photoexcitation/Auger decay process: Auger-photoelectron coincidence spectroscopy study

    International Nuclear Information System (INIS)

    The N23VV Auger spectrum of Ru has been measured in coincidence with 4p1/2 and with 4p3/2 photoelectrons. Unlike other metals that exhibit bandlike Auger decays, we find that the two Auger spectra are not shifted by the difference in core level binding energies. A consistent description of these transitions and the core level line shape requires consideration of the relativistic multiplet splitting in the intermediate core hole state and two-valence-hole Auger final state. The results suggest that the large linewidth of the 4p levels is primarily due to multiplet splitting, and that an N2(N3N45)N45N45 super-Coster-Kronig transition is only a minor decay channel. (c) 2000 The American Physical Society

  18. CeO{sub x}/Al{sub 2}O{sub 3} thin films on stainless steel substrate — Dynamical X-ray photoelectron spectroscopy investigations

    Energy Technology Data Exchange (ETDEWEB)

    Avramova, Ivalina, E-mail: iva@svr.igic.bas.bg [Department of Chemistry, Bilkent University, Ankara 06800 (Turkey); Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1113 (Bulgaria); Suzer, Sefik [Department of Chemistry, Bilkent University, Ankara 06800 (Turkey); Guergova, Desislava; Stoychev, Dimitar [Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia 1113 (Bulgaria); Stefanov, Plamen [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1113 (Bulgaria)

    2013-06-01

    The CeO{sub x}/Al{sub 2}O{sub 3} thin films on stainless steel with different ceria loading were subjected to a.c. (square wave) pulses at various frequencies in the range 10{sup −3} to 100 kHz while recording X-ray photoelectron spectra. The resulting binding energy differences were derived from the frequency dependence of the corresponding Al2p, Ce3d and O1s peaks. At low ceria loadings the main constituent on the surface is CeAlO{sub 3} phase, while for high ceria loading the film is constructed from CeO{sub 2} and CeAlO{sub 3} phases spread over the Al{sub 2}O{sub 3}. Accordingly, it was observed that the ceria loading determines the conductivities of the investigated thin oxide films. - Highlights: • This work contributes to CeO{sub x}/Al{sub 2}O{sub 3} thin films on stainless steel as catalysts. • Dynamical X-ray photoelectron spectroscopy measurements were demonstrated. • The film conductivity could be controlled by the ceria loading. • The Ce{sup 3+} frequency response depends on the host oxide matrix.

  19. Evaluation of valence band top and electron affinity of SiO2 and Si-based semiconductors using X-ray photoelectron spectroscopy

    Science.gov (United States)

    Fujimura, Nobuyuki; Ohta, Akio; Makihara, Katsunori; Miyazaki, Seiichi

    2016-08-01

    An evaluation method for the energy level of the valence band (VB) top from the vacuum level (VL) for metals, dielectrics, and semiconductors from the results of X-ray photoelectron spectroscopy (XPS) is presented for the accurate determination of the energy band diagram for materials of interest. In this method, the VB top can be determined by the energy difference between the onset of VB signals and the cut-off energy for secondary photoelectrons by considering the X-ray excitation energy (hν). The energy level of the VB top for three kinds of Si-based materials (H-terminated Si, wet-cleaned 4H-SiC, and thermally grown SiO2) has been investigated by XPS under monochromatized Al Kα radiation (hν = 1486.6 eV). We have also demonstrated the determination of the electron affinity for the samples by this measurement technique in combination with the measured and reported energy bandgaps (E g).

  20. Photoelectron spectroscopy of boron-gold alloy clusters and boron boronyl clusters: B3Au(n)(-) and B3(BO)n(-) (n = 1, 2).

    Science.gov (United States)

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

    2013-07-28

    Photoelectron spectroscopy and density-functional theory are combined to study the structures and chemical bonding in boron-gold alloy clusters and boron boronyl clusters: B3Au(n)(-) and B3(BO)n(-) (n = 1, 2). Vibrationally resolved photoelectron spectra are obtained for all four species and the B-Au and B-BO clusters exhibit similar spectral patterns, with the latter species having higher electron binding energies. The electron affinities of B3Au, B3Au2, B3(BO), and B3(BO)2 are determined to be 2.29 ± 0.02, 3.17 ± 0.03, 2.71 ± 0.02, and 4.44 ± 0.02 eV, respectively. The anion and neutral clusters turn out to be isostructural and isovalent to the B3H(n)(-)∕B3H(n) (n = 1, 2) species, which are similar in bonding owing to the fact that Au, BO, and H are monovalent σ ligands. All B3Au(n)(-) and B3(BO)n(-) (n = 1, 2) clusters are aromatic with 2π electrons. The current results provide new examples for the Au∕H and BO∕H isolobal analogy and enrich the chemistry of boronyl and gold. PMID:23901981