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Sample records for polarized photoelectron diffraction

  1. Polarity of wurtzite crystals by photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Bartoš, Igor; Romanyuk, Olexandr

    2014-01-01

    Roč. 315, OCT (2014), s. 506-509 ISSN 0169-4332 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : wurtzite semiconductors * surface polarity * X-ray photoelectron diffraction * XPD Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.711, year: 2014 http://www.sciencedirect.com/science/article/pii/S016943321400066X

  2. GaN polarity determination by photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Jiříček, Petr; Paskova, T.; Bieloshapka, Igor; Bartoš, Igor

    2013-01-01

    Roč. 103, č. 9 (2013), "091601-1"-"091601-4" ISSN 0003-6951 R&D Projects: GA ČR(CZ) GBP108/12/G108 Grant - others:AV ČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaN * photoelectron diffraction * wurtzite * surface polarity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.515, year: 2013 http://apl.aip.org/resource/1/applab/v103/i9/p091601_s1?isAuthorized=no

  3. Magnetic x-ray circular dichroism in spin-polarized photoelectron diffraction

    International Nuclear Information System (INIS)

    Waddill, G.D.; Tobin, J.G.

    1994-01-01

    The first structural determination with spin-polarized, energy-dependent photoelectron diffraction using circularly-polarized x-rays is reported for Fe films on Cu(001). Circularly-polarized x-rays produced spin-polarized photoelectrons from the Fe 2p doublet, and intensity asymmetries in the 2p 3/2 level are observed. Fully spin-specific multiple scattering calculations reproduced the experimentally-determined energy and angular dependences. A new analytical procedure which focuses upon intensity variations due to spin-dependent diffraction is introduced. A sensitivity to local geometric and magnetic structure is demonstrated

  4. GaN quantum dot polarity determination by X-ray photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Bartoš, Igor; Brault, J.; De Mierry, P.; Paskova, T.; Jiříček, Petr

    2016-01-01

    Roč. 389, Dec (2016), s. 1156-1160 ISSN 0169-4332 R&D Projects: GA ČR GA15-01687S; GA MŠk LM2015088 Institutional support: RVO:68378271 Keywords : GaN * semipolar GaN * quantum dots * X-ray photoelectron diffraction * surface polarity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.387, year: 2016

  5. Non-destructive assessment of the polarity of GaN nanowire ensembles using low-energy electron diffraction and x-ray photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Fernández-Garrido, S.; Jiříček, Petr; Bartoš, Igor; Geelhaar, L.; Brandt, O.; Paskova, T.

    2015-01-01

    Roč. 106, č. 2 (2015), "021602-1"-"021602-4" ISSN 0003-6951 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaN nanowires * X-ray photoelectron diffraction * LEED I-V * GaN polarity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.142, year: 2015

  6. Polarity of GaN with polar {0001} and semipolar {1011}, {2021}, {1122}, orientations by x-ray photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Jiříček, Petr; Paskova, T.; Bartoš, Igor

    2015-01-01

    Roč. 30, č. 19 (2015), 2881-2892 ISSN 0884-2914 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaN , * semipolar surfaces, * photoelectron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.579, year: 2015

  7. Investigation of the near-surface structures of polar InN films by chemical-state-discriminated hard X-ray photoelectron diffraction

    International Nuclear Information System (INIS)

    Yang, A. L.; Yamashita, Y.; Kobata, M.; Yoshikawa, H.; Sakata, O.; Kobayashi, K.; Matsushita, T.; Píš, I.; Imura, M.; Yamaguchi, T.; Nanishi, Y.

    2013-01-01

    Near-surface structures of polar InN films were investigated by laboratory-based hard X-ray photoelectron diffraction (HXPD) with chemical-state-discrimination. HXPD patterns from In 3d 5/2 and N 1s core levels of the In-polar and N-polar InN films were different from each other and compared with the simulation results using a multiple-scattering cluster model. It was found that the near-surface structure of the In-polar InN film was close to the ideal wurtzite structure. On the other hand, on the N-polar InN film, defects-rich surface was formed. In addition, the existence of the In-polar domains was observed in the HXPD patterns.

  8. 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...... effects will lead to an apparent temporal shift of 50 as between photoelectrons from a 2p and 1s state in atomic hydrogen....

  9. Full k-space visualization of photoelectron diffraction

    International Nuclear Information System (INIS)

    Denlinger, J.D.; Rotenberg, E.; Kevan, S.D.; Tonner, B.P.

    1997-01-01

    The development of photoelectron holography has promoted the need for larger photoelectron diffraction data sets in order to improve the quality of real-space reconstructed images (by suppressing transformational artifacts and distortions). The two main experimental and theoretical approaches to holography, the transform of angular distribution patterns for a coarse selection of energies or the transform of energy-scanned profiles for several directions, represent two limits to k-space sampling. The high brightness of third-generation soft x-ray synchrotron sources provides the opportunity to rapidly measure large high-density x-ray photoelectron diffraction (XPD) data sets with approximately uniform k-space sampling. In this abstract, the authors present such a photoelectron data set acquired for Cu 3p emission from Cu(001). Cu(001) is one of the most well-studied systems for understanding photoelectron diffraction structure and for testing photoelectron holography methods. Cu(001) was chosen for this study in part due to the relatively inert and unreconstructed clean surface, and it served to calibrate and fine-tune the operation of a new synchrotron beamline, electron spectrometer and sample goniometer. In addition to Cu, similar open-quotes volumeclose quotes XPD data sets have been acquired for bulk and surface core-level emission from W(110), from reconstructed Si(100) and Si(111) surfaces, and from the adsorbate system of c(2x2) Mn/Ni(100)

  10. Polarity of semipolar wurtzite crystals: X-ray photoelectron diffraction from GaN{10-11} and GaN{20-21} surfaces

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Jiříček, Petr; Paskova, T.; Bartoš, Igor

    2014-01-01

    Roč. 116, č. 10 (2014), "104909-1"-"104909-6" ISSN 0021-8979 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : nitride compounds * XPD * low-energy electron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.183, year: 2014

  11. Photoelectron diffraction and holography: Present status and future prospects

    Energy Technology Data Exchange (ETDEWEB)

    Fadley, C.S. [California Univ., Davis, CA (United States). Dept. of Physics]|[Lawrence Berkeley Lab., CA (United States); Thevuthasan, S. [California Univ., Davis, CA (United States). Dept. of Physics; Kaduwela, A.P. [Lawrence Berkeley Lab., CA (United States)] [and others

    1993-07-01

    Photoelectron diffraction and photoelectron holography, a newly developed variant of it, can provide a rich range of information concerning surface structure. These methods are sensitive to atomic type, chemical state, and spin state. The theoretical prediction of diffraction patterns is also well developed at both the single scattering and multiple scattering levels, and quantitative fits of experiment to theory can lead to structures with accuracies in the {plus_minus}0.03 {Angstrom} range. Direct structural information can also be derived from forward scattering in scanned-angle measurements at higher energies, path length differences contained in scanned-energy data at lower energies, and holographic inversions of data sets spanning some region in angle and energy space. Diffraction can also affect average photoelectron emission depths. Circular dichroism in core-level emission can be fruitfully interpreted in terms of photoelectron diffraction theory, as can measurements with spin-resolved core-spectra, and studies of surface magnetic structures and phase transitions should be possible with these methods. Synchrotron radiation is a key element of fully utilizing these techniques.

  12. Theory and Application of Photoelectron Diffraction for Complex Oxide Systems

    Science.gov (United States)

    Chassé, Angelika; Chassé, Thomas

    2018-06-01

    X-ray photoelectron diffraction (XPD) has been used to investigate film structures and local sites of surface and dopant atoms in complex oxide materials. We have performed angular-resolved measurements of intensity distribution curves (ADCs) and patterns (ADPs) of elemental core level intensities from binary to quaternary mixed oxide samples and compared them to multiple-scattering cluster (MSC) calculations in order to derive information on structural models and related parameters. MSC calculations permitted to describe both bulk diffraction features of binary oxide MnO(001) and the thickness-dependence of the tetragonal distortion of epitaxial MnO films on Ag(001). XPD was further used to investigate the surface termination of perovskite SrTiO3 and BaTiO3 substrates in order to evaluate influence of different ex situ and in situ preparation procedures on the surface layers, which are crucial for quality of following film growth. Despite the similarity of local environments of Sr (Ba) and Ti atoms in the perovskite film structure an angular region in the ADCs was identified as a fingerprint with the help of MSC simulations which provided clear conclusions on the perovskite oxide surfaces. Dopant sites in quaternary perovskite manganites La1-xCaxMnO3, La1-xSrxMnO3, and La1-xCexMnO3 were studied with polar angle scans of the photoemission intensities of host and dopant atoms. Both direct comparison of experimental ADCs and to the simulations within MSC models confirm the occupation of A sites by the dopants and the structural quality of the complex oxide films.

  13. Holographic Reconstruction of Photoelectron Diffraction and Its Circular Dichroism for Local Structure Probing

    Science.gov (United States)

    Matsui, Fumihiko; Matsushita, Tomohiro; Daimon, Hiroshi

    2018-06-01

    The local atomic structure around a specific element atom can be recorded as a photoelectron diffraction pattern. Forward focusing peaks and diffraction rings around them indicate the directions and distances from the photoelectron emitting atom to the surrounding atoms. The state-of-the-art holography reconstruction algorithm enables us to image the local atomic arrangement around the excited atom in a real space. By using circularly polarized light as an excitation source, the angular momentum transfer from the light to the photoelectron induces parallax shifts in these diffraction patterns. As a result, stereographic images of atomic arrangements are obtained. These diffraction patterns can be used as atomic-site-resolved probes for local electronic structure investigation in combination with spectroscopy techniques. Direct three-dimensional atomic structure visualization and site-specific electronic property analysis methods are reviewed. Furthermore, circular dichroism was also found in valence photoelectron and Auger electron diffraction patterns. The investigation of these new phenomena provides hints for the development of new techniques for local structure probing.

  14. Photoelectron diffraction of magnetic ultrathin films: Fe/Cu(001)

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G. (Lawrence Livermore National Lab., CA (USA)); Wagner, M.K. (Wisconsin Univ., Madison, WI (USA). Dept. of Chemistry); Guo, X.Q.; Tong, S.Y. (Wisconsin Univ., Milwaukee, WI (USA). Dept. of Physics)

    1991-01-03

    The preliminary results of an ongoing investigation of Fe/Cu(001) are presented here. Energy dependent photoelectron diffraction, including the spin-dependent variant using the multiplet split Fe3s state, is being used to investigate the nanoscale structures formed by near-monolayer deposits of Fe onto Cu(001). Core-level photoemission from the Fe3p and Fe3s states has been generated using synchrotron radiation as the tunable excitation source. Tentatively, a comparison of the experimental Fe3p cross section measurements with multiple scattering calculations indicates that the Fe is in a fourfold hollow site with a spacing of 3.6{Angstrom} between it and the atom directly beneath it, in the third layer. This is consistent with an FCC structure. The possibility of utilizing spin-dependent photoelectron diffraction to investigate magnetic ultrathin films will be demonstrated, using our preliminary spectra of the multiplet-split Fe3s os near-monolayer Fe/Cu(001). 18 refs., 10 figs.

  15. Global search in photoelectron diffraction structure determination using genetic algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Viana, M L [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil); Muino, R Diez [Donostia International Physics Center DIPC, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain); Soares, E A [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil); Hove, M A Van [Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China); Carvalho, V E de [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil)

    2007-11-07

    Photoelectron diffraction (PED) is an experimental technique widely used to perform structural determinations of solid surfaces. Similarly to low-energy electron diffraction (LEED), structural determination by PED requires a fitting procedure between the experimental intensities and theoretical results obtained through simulations. Multiple scattering has been shown to be an effective approach for making such simulations. The quality of the fit can be quantified through the so-called R-factor. Therefore, the fitting procedure is, indeed, an R-factor minimization problem. However, the topography of the R-factor as a function of the structural and non-structural surface parameters to be determined is complex, and the task of finding the global minimum becomes tough, particularly for complex structures in which many parameters have to be adjusted. In this work we investigate the applicability of the genetic algorithm (GA) global optimization method to this problem. The GA is based on the evolution of species, and makes use of concepts such as crossover, elitism and mutation to perform the search. We show results of its application in the structural determination of three different systems: the Cu(111) surface through the use of energy-scanned experimental curves; the Ag(110)-c(2 x 2)-Sb system, in which a theory-theory fit was performed; and the Ag(111) surface for which angle-scanned experimental curves were used. We conclude that the GA is a highly efficient method to search for global minima in the optimization of the parameters that best fit the experimental photoelectron diffraction intensities to the theoretical ones.

  16. DEVELOPMENT OF NEXT-GENERATION DETECTORS AND INSTRUMENTATION FOR PHOTOELECTRON SPECTROSCOPY, DIFFRACTION AND HOLOGRAPHY

    International Nuclear Information System (INIS)

    Charles S. Fadley, Principal Investigator

    2005-01-01

    We have developed a new multichannel detector for use in photoelectron spectroscopy (as well as other types of high-count-rate spectroscopy) that will operate at rates of up to 1 GHz. Such detectors are crucial to the full utilization of the high-brightness radiation generated by third-generation synchrotron radiation sources. In addition, new software and hardware has been developed to permit rapidly and accurately scanning photoelectron spectra that will be accumulated in as little as a 200 micros. A versatile next-generation sample goniometer permitting equally rapid scanning of specimen angles or photon energies for angle-resolved photoemission studies, photoelectron diffraction, and photoelectron holography measurements, and cooling to below 10K has also been designed and constructed. These capabilities have been incorporated into a unique photoelectron spectrometer/diffractometer at the Advanced Light Source of the Lawrence Berkeley National Laboratory; this experimental system includes ultrahigh energy resolution, in situ rotation, variable polarization, and optional spin detection. This overall system is now being used in studies of a variety of problems including magnetic metals and oxides; metal/metal, metal/metal oxide, and metal-oxide/metal-oxide multilayers; and systems exhibiting giant and colossal magnetoresistance

  17. Using photoelectron diffraction to determine complex molecular adsorption structures

    International Nuclear Information System (INIS)

    Woodruff, D P

    2010-01-01

    Backscattering photoelectron diffraction, particularly in the energy-scan mode, is now an established technique for determining in a quantitative fashion the local structure of adsorbates on surfaces, and has been used successfully for ∼100 adsorbate phases. The elemental and chemical-state specificity afforded by the characteristic core level photoelectron binding energies means that it has particular advantages for molecular adsorbates, as the local geometry of inequivalent atoms in the molecule can be determined in a largely independent fashion. On the other hand, polyatomic molecules present a general problem for all methods of surface structure determination in that a mismatch of intramolecular distances with interatomic distances on the substrate surface means that the atoms in the adsorbed molecule are generally in low-symmetry sites. The quantities measured experimentally then represent an incoherent sum of the properties of each structural domain that is inequivalent with respect to the substrate point group symmetry. This typically leads to greater ambiguity or precision in the structural solutions. The basic principles of the method are described and illustrated with a simple example involving molecule/substrate bonding through only one constituent atom (TiO 2 -(110)/H 2 O). This example demonstrates the importance of obtaining quantitative local structural information. Further examples illustrate both the successes and the problems of this approach when applied to somewhat more complex molecular adsorbates.

  18. Polarization of photoelectrons produced from atoms by synchrotron radiation

    International Nuclear Information System (INIS)

    Hughes, V.W.; Lu, D.C.; Huang, K.N.

    1981-01-01

    The polarization of photoelectrons from stoms has proved to be an important tool for studying correlation effects in atoms, as well as relativistic effects such as the spin-orbit interaction. Extensive experimental and theoretical studies have been made of the Fano effect, which is the production of polarized electrons by photoionization of unpolarized atoms by circularly polarized light. The experiments have dealt mostly with alkali atoms and with photon energies slightly above the ionization thresholds. Measurements that could be made to utilize polarized radiation are discussed

  19. Molecular photoelectron holography with circularly polarized laser pulses.

    Science.gov (United States)

    Yang, Weifeng; Sheng, Zhihao; Feng, Xingpan; Wu, Miaoli; Chen, Zhangjin; Song, Xiaohong

    2014-02-10

    We investigate the photoelectron momentum distribution of molecular-ion H2+driven by ultrashort intense circularly polarized laser pulses. Both numerical solutions of the time-dependent Schrödinger equation (TDSE) and a quasiclassical model indicate that the photoelectron holography (PH) with circularly polarized pulses can occur in molecule. It is demonstrated that the interference between the direct electron wave and rescattered electron wave from one core to its neighboring core induces the PH. Moreover, the results of the TDSE predict that there is a tilt angle between the interference pattern of the PH and the direction perpendicular to the molecular axis. Furthermore, the tilt angle is sensitively dependent on the wavelength of the driven circularly polarized pulse, which is confirmed by the quasiclassical calculations. The PH induced by circularly polarized laser pulses provides a tool to resolve the electron dynamics and explore the spatial information of molecular structures.

  20. Renormalized multiple-scattering theory of photoelectron diffraction

    International Nuclear Information System (INIS)

    Biagini, M.

    1993-01-01

    The current multiple-scattering cluster techniques for the calculation of x-ray photoelectron and Auger-electron diffraction patterns consume much computer time in the intermediate-energy range (200--1000 eV); in fact, because of the large value of the electron mean free path and of the large forward-scattering amplitude at such energies, the electron samples a relatively large portion of the crystal, so that the number of paths to be considered becomes dramatically high. An alternative method is developed in the present paper: instead of calculating the individual contribution from each single path, the scattering matrix of each plane parallel to the surface is calculated with a renormalization process that calculates every scattering event in the plane up to infinite order. Similarly the scattering between two planes is calculated up to infinite order, and the double-plane scattering matrix is introduced. The process may then be applied to the calculation of a larger set of atomic layers. The advantage of the method is that a relatively small number of internuclear vectors have been used to obtain convergence in the calculation

  1. Photoelectron diffraction studies of small adsorbates on single crystal surfaces

    International Nuclear Information System (INIS)

    Pascal, Mathieu

    2002-01-01

    The structural determination of small molecules adsorbed on single crystal surfaces has been investigated using scanned energy mode photoelectron diffraction (PhD). The experimental PhD data were compared to theoretical models using a simulation program based on multiple scattering calculations. Three adsorption systems have been examined on Ag(110), Cu(110) and Cu(111) crystals. The structure of the (2x1)-O adsorption phase on Ag(110) revealed that the O atoms occupied the long bridge site and are almost co-planar with the top layer of Ag atoms. The best agreement between multiple scattering theory and experiment has been obtained for a missing-row (or equivalently an 'added- row') reconstruction. Alternative buckled-row and unreconstructed surface models can be excluded. The adsorption of the benzoate species on Cu(110) has been found to occur via the carboxylate group. The molecules occupy short bridge sites with the O atoms being slightly displaced from atop sites and are aligned along the close-packed azimuth. The tilt of the molecule with respect to the surface and the degree to which the surface is relaxed have also been investigated. The adsorption of methyl on Cu(111) was studied using either azomethane or methyl iodide to prepare the surface layers. At saturation coverage the preferred adsorption site is the fcc threefold hollow site, whereas at half saturation coverage ∼ 30 % of the methyl species occupy the hop threefold hollow sites. Best agreement between theory and experiment corresponded to a methyl group adsorbed with C 3v symmetry. The height of the C above the surface in a pure methyl layer was 1.66 ± 0.02 A, but was reduced to 1.62 ± 0.02 A in the presence of co-adsorbed iodine, suggesting that iodine increases the strength of adsorption. Iodine was also found to occupy the fee threefold hollow sites with a Cu-l bondlength of 2.61 ± 0.02 A. (author)

  2. Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

    DEFF Research Database (Denmark)

    Boll, Rebecca; Rouzee, Arnaud; Adolph, Marcus

    2014-01-01

    This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular...

  3. Structure determination by photoelectron diffraction of small molecules on surfaces

    International Nuclear Information System (INIS)

    Booth, N.A.

    1998-05-01

    The synchrotron radiation based technique of Photoelectron Diffraction (PhD) has been applied to three adsorption systems. Structure determinations, are presented for each system which involve the adsorption of small molecules on the low index {110} plane of single crystal Cu and Ni substrates. For the NH 3 -Cu(110) system PhD was successful in determining a N-Cu bondlength of 2.05 ± 0.03 A as well as values for the anisotropic vibrational amplitudes of the N and an expansion of the 1st to 2nd Cu substrate layer spacing from the bulk value of 0.08 ± 0.08 A. The most significant and surprising structural parameter determined for this system was that the N atom occupies an asymmetric adsorption site. Rather than being situated in the expected high symmetry atop site the N atom was found to be offset parallel to the surface by 0.37 ± 0.12 A in the [001] azimuth. In studying the glycine-Cu(110) system the adsorption structure of an amino-acid has been quantified. The local adsorption geometries of all the atoms involved in the molecule to surface bond have been determined. The glycine molecule is found to be bonded to the surface via both its amino and carboxylate functional groups. The molecule straddles two [11-bar0] rows of the Cu substrate. The two O atoms are found to be in identical sites both approximately atop Cu atoms on the [11-bar0] rows offset parallel to the surface by 0.80 ± 0.05 A in the [001] azimuth, the O-Cu bondlength was found to be 2.03 ± 0.05 A. The N atom was also found to adsorb in an approximately atop geometry but offset parallel to the surface by 0.24 ± 0.10A in the [11-bar0] direction, the N-Cu bondlength was found to be 2.05± 0.05 A. PhD was unsuccessful in determining the positions of the two C atoms that form a bridge between the two functional groups bonded to the surface due to difficulties in separating the two inequivalent contributions to the final intensity modulation function. For the CN-Ni(110) system both PhD and Near Edge

  4. Diffraction efficiency calculations of polarization diffraction gratings with surface relief

    Science.gov (United States)

    Nazarova, D.; Sharlandjiev, P.; Berberova, N.; Blagoeva, B.; Stoykova, E.; Nedelchev, L.

    2018-03-01

    In this paper, we evaluate the optical response of a stack of two diffraction gratings of equal one-dimensional periodicity. The first one is a surface-relief grating structure; the second, a volume polarization grating. This model is based on our experimental results from polarization holographic recordings in azopolymer films. We used films of commercially available azopolymer (poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt]), shortly denoted as PAZO. During the recording process, a polarization grating in the volume of the material and a relief grating on the film surface are formed simultaneously. In order to evaluate numerically the optical response of this “hybrid” diffraction structure, we used the rigorous coupled-wave approach (RCWA). It yields stable numerical solutions of Maxwell’s vector equations using the algebraic eigenvalue method.

  5. Femtosecond x-ray photoelectron diffraction on gas-phase dibromobenzene molecules

    International Nuclear Information System (INIS)

    Rolles, D; Boll, R; Epp, S W; Erk, B; Foucar, L; Hömke, A; Adolph, M; Gorkhover, T; Aquila, A; Chapman, H N; Coppola, N; Delmas, T; Gumprecht, L; Holmegaard, L; Bostedt, C; Bozek, J D; Coffee, R; Decleva, P; Filsinger, F; Johnsson, P

    2014-01-01

    We present time-resolved femtosecond photoelectron momentum images and angular distributions of dissociating, laser-aligned 1,4-dibromobenzene (C 6 H 4 Br 2 ) molecules measured in a near-infrared pump, soft-x-ray probe experiment performed at an x-ray free-electron laser. The observed alignment dependence of the bromine 2p photoelectron angular distributions is compared to density functional theory calculations and interpreted in terms of photoelectron diffraction. While no clear time-dependent effects are observed in the angular distribution of the Br(2p) photoelectrons, other, low-energy electrons show a pronounced dependence on the time delay between the near-infrared laser and the x-ray pulse. (paper)

  6. Ionization in elliptically polarized pulses: Multielectron polarization effects and asymmetry of photoelectron momentum distributions

    DEFF Research Database (Denmark)

    Shvetsov-Shilovskiy, Nikolay; Dimitrovski, Darko; Madsen, Lars Bojer

    2012-01-01

    In the tunneling regime we present a semiclassical model of above-threshold ionization with inclusion of the Stark shift of the initial state, the Coulomb potential, and a polarization induced dipole potential. The model is used for the investigation of the photoelectron momentum distributions...... in close to circularly polarized light, and it is validated by comparison with ab initio results and experiments. The momentum distributions are shown to be highly sensitive to the tunneling exit point, the Coulomb force, and the dipole potential from the induced dipole in the atomic core...

  7. Complete k-space visualization of x-ray photoelectron diffraction

    International Nuclear Information System (INIS)

    Denlinger, J.D.; Lawrence Berkeley Lab., CA; Rotenberg, E.; Lawrence Berkeley Lab., CA; Kevan, S.D.; Tonner, B.P.

    1996-01-01

    A highly detailed x-ray photoelectron diffraction data set has been acquired for crystalline Cu(001). The data set for bulk Cu 3p emission encompasses a large k-space volume (k = 3--10 angstrom -1 ) with sufficient energy and angular sampling to monitor the continuous variation of diffraction intensities. The evolution of back-scattered intensity oscillations is visualized by energy and angular slices of this volume data set. Large diffraction data sets such as this will provide rigorous experimental tests of real-space reconstruction algorithms and multiple-scattering simulations

  8. Theoretical investigation of the (e,2e) simulation of photoelectron spectroscopy of polarized atoms

    International Nuclear Information System (INIS)

    Cherepkov, N.A.; Kuznetsov, V.V.

    1992-01-01

    It is shown that the (e, 2e) simulation of the photionization process can be used to perform the complete quantum-mechanical experiment provided the target atoms are polarized. The experimental technique developed earlier for simulation of the photoelectron angular distribution measurements can be used to obtain three additional parameters in the case of polarized atoms. (Author)

  9. Vector wave diffraction pattern of slits masked by polarizing devices

    Indian Academy of Sciences (India)

    This calls for a systematic study of diffraction properties of different apertures using polarization-sensitive devices. In the present paper, we have studied the Fraunhofer diffraction pattern of slits masked by different kinds of polarizing devices which introduce a phase difference between the two orthogonal components of the ...

  10. Photoelectron diffraction study of Rh nanoparticles growth on Fe3O4/Pd(111) ultrathin film

    International Nuclear Information System (INIS)

    Abreu, G. J. P.; Pancotti, A; Lima, L. H. de; Landers, R.; Siervo, A. de

    2013-01-01

    Metallic nanoparticles (NPs) supported on oxides thin films are commonly used as model catalysts for studies of heterogeneous catalysis. Several 4d and 5d metal NPs (for example, Pd, Pt and Au) grown on alumina, ceria and titania have shown strong metal support interaction (SMSI), for instance the encapsulation of the NPs by the oxide. The SMSI plays an important role in catalysis and is very dependent on the support oxide used. The present work investigates the growth mechanism and atomic structure of Rh NPs supported on epitaxial magnetite Fe 3 O 4 (111) ultrathin films prepared on Pd(111) using the Molecular Beam Epitaxy (MBE) technique. The iron oxide and the Rh NPs were characterized using X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction and photoelectron diffraction (PED). The combined XPS and PED results indicate that Rh NPs are metallic, cover approximately 20 % of the iron oxide surface and show height distribution ranging 3–5 ML (monolayers) with essentially a bulk fcc structure.

  11. Scanned-energy mode photoelectron diffraction measurements at beamline 7.0.1

    International Nuclear Information System (INIS)

    Toomes, R.; Booth, N.A.; Woodruff, D.P.

    1997-01-01

    This report covers the results of the authors first experimental run, in May 1996, conducted to explore the advantages offered by the high spectral resolution available at the SpectroMicroscopy Facility on beam line 7.0 to conduct scanned-energy mode photoelectron diffraction (PhD). This technique is now a well-established method for the determination of local structure of atomic and molecular adsorbates on well-characterised surfaces. The directly-emitted component of an adsorbate core-level photoelectron wavefield interferes coherently with components of the same wavefield elastically scattered by surrounding atoms, leading to a modulation in the photoemission intensity as a function of kinetic energy in any specific emission direction. A series of such PhD modulation spectra, each typically covering energies from 50-500 eV, for a series of different emission directions, provides the basis for a quantitative structure determination of the emitter-scatterer geometry. Within the last years the authors have developed an integrated approach to extract the structural information from these photoelectron diffraction (PhD) spectra in a quantitative way. A direct data inversion technique (the so-called Projection method) provides a first-order estimate of the local adsorbate geometry in the form of an 'image' of the scatterer atoms which are nearest neighbours to the emitter. This information is then used as a starting model for optimisation of the structural parameters by comparing the experimental PhD spectra with the results of multiple scattering simulations using a code developed by Fritzsche. The optimisation uses an automated trial-and-error procedure by minimising a reliability factor which provides an objective measure of the quality of agreement between experiment and theory. The authors have successfully applied this approach to the structure determination of about 30 adsorption systems

  12. Scanned-energy mode photoelectron diffraction measurements at beamline 7.0.1

    Energy Technology Data Exchange (ETDEWEB)

    Toomes, R.; Booth, N.A.; Woodruff, D.P. [Univ. of Warwick, Coventry (United Kingdom)] [and others

    1997-04-01

    This report covers the results of the authors first experimental run, in May 1996, conducted to explore the advantages offered by the high spectral resolution available at the SpectroMicroscopy Facility on beam line 7.0 to conduct scanned-energy mode photoelectron diffraction (PhD). This technique is now a well-established method for the determination of local structure of atomic and molecular adsorbates on well-characterised surfaces. The directly-emitted component of an adsorbate core-level photoelectron wavefield interferes coherently with components of the same wavefield elastically scattered by surrounding atoms, leading to a modulation in the photoemission intensity as a function of kinetic energy in any specific emission direction. A series of such PhD modulation spectra, each typically covering energies from 50-500 eV, for a series of different emission directions, provides the basis for a quantitative structure determination of the emitter-scatterer geometry. Within the last years the authors have developed an integrated approach to extract the structural information from these photoelectron diffraction (PhD) spectra in a quantitative way. A direct data inversion technique (the so-called Projection method) provides a first-order estimate of the local adsorbate geometry in the form of an `image` of the scatterer atoms which are nearest neighbours to the emitter. This information is then used as a starting model for optimisation of the structural parameters by comparing the experimental PhD spectra with the results of multiple scattering simulations using a code developed by Fritzsche. The optimisation uses an automated trial-and-error procedure by minimising a reliability factor which provides an objective measure of the quality of agreement between experiment and theory. The authors have successfully applied this approach to the structure determination of about 30 adsorption systems.

  13. Photoelectron diffraction k-space volumes of the c(2x2) Mn/Ni(100) structure

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, S.; Denlinger, J.; Chen, X. [Univ. of Wisconsin, Milwaukee, WI (United States)] [and others

    1997-04-01

    Traditionally, x-ray photoelectron diffraction (XPD) studies have either been done by scanning the diffraction angle for fixed kinetic energy (ADPD), or scanning the kinetic energy at fixed exit angle (EDPD). Both of these methods collect subsets of the full diffraction pattern, or volume, which is the intensity of photoemission as a function of momentum direction and magnitude. With the high density available at the Spectromicroscopy Facility (BL 7.0) {open_quotes}ultraESCA{close_quotes} station, the authors are able to completely characterize the photoelectron diffraction patterns of surface structures, up to several hundred electron volts kinetic energy. This large diffraction `volume` can then be analyzed in many ways. The k-space volume contains as a subset the energy dependent photoelectron diffraction spectra along all emission angles. It also contains individual, hemispherical, diffraction patterns at specific kinetic energies. Other `cuts` through the data set are also possible, revealing new ways of viewing photoelectron diffraction data, and potentially new information about the surface structure being studied. In this article the authors report a brief summary of a structural study being done on the c(2x2) Mn/Ni(100) surface alloy. This system is interesting for both structural and magnetic reasons. Magnetically, the Mn/Ni(100) surface alloy exhibits parallel coupling of the Mn and Ni moments, which is opposite to the reported coupling for the bulk, disordered, alloy. Structurally, the Mn atoms are believed to lie well above the surface plane.

  14. Diffraction of polarized light on periodic structures

    International Nuclear Information System (INIS)

    Bukanina, V; Divakov, D; Tyutyunnik, A; Hohlov, A

    2012-01-01

    Periodic structures as photonic crystals are widely used in modern laser devices, communication technologies and for creating various beam splitters and filters. Diffraction gratings are applied for creating 3D television sets, DVD and Blu-ray drives and reflective structures (Berkley mirror). It is important to simulate diffraction on such structures to design optical systems with predetermined properties based on photonic crystals and diffraction gratings. Methods of simulating diffraction on periodic structures uses theory of Floquet-Bloch and rigorous coupled-wave analysis (RCWA). Current work is dedicated to analysis of photonic band gaps and simulating diffraction on one-dimensional binary diffraction grating using RCWA. The Maxwell's equations for isotropic media and constitutive relations based on the cgs system were used as a model.

  15. Photoelectron linear accelerator for producing a low emittance polarized electron beam

    Science.gov (United States)

    Yu, David U.; Clendenin, James E.; Kirby, Robert E.

    2004-06-01

    A photoelectron linear accelerator for producing a low emittance polarized electric beam. The accelerator includes a tube having an inner wall, the inner tube wall being coated by a getter material. A portable, or demountable, cathode plug is mounted within said tube, the surface of said cathode having a semiconductor material formed thereon.

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

    International Nuclear Information System (INIS)

    Tobin, James; Yu, Sung; Chung, Brandon; Morton, Simon; Komesu, Takashi; Waddill, George

    2008-01-01

    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.

  17. Polarization and dipole effects in hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Novak, M. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. F. D. Roosevelt, B-1050 Brussels (Belgium); Pauly, N., E-mail: nipauly@ulb.ac.be [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. F. D. Roosevelt, B-1050 Brussels (Belgium); Dubus, A. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. F. D. Roosevelt, B-1050 Brussels (Belgium)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer X-rays are unpolarized or linearly polarized. Black-Right-Pointing-Pointer A difference of polarization implies a variation in path travelled by the photoelectrons. Black-Right-Pointing-Pointer We show the influence of the polarization on the partial intensity distributions. Black-Right-Pointing-Pointer We also point out the influence of the dipole approximation. Black-Right-Pointing-Pointer We use Monte Carlo simulations. - Abstract: Hard X-ray photoelectron spectroscopy (HXPS) using X-rays in the 1.5-15 keV energy range generated by synchrotron sources becomes an increasingly important analysis technique due to its potential for bulk sensitive measurements. However, besides their high energy, another characteristic of photons generated by synchrotron sources is their linear polarization while X-rays from Al K{alpha} or Mg K{alpha} for instance are unpolarized. This difference implies a possible variation in total path travelled by the photoelectrons generated by the X-rays inside the medium and consequently a modification of the resulting spectrum shape. We show the influence of the polarization on the partial intensity distributions, namely the number of electrons escaping after n inelastic scattering events, for photoelectron with energies of 0.5, 1, 2, 3, 4 and 5 keV and originating from Si 1s{sub 1/2}, Cu 1s{sub 1/2}, Cu 2p{sub 3/2}, Au 4d{sub 3/2} and Au 4f{sub 7/2} subshells. Moreover, we point out the influence of the dipole approximation leading to an underestimation of the partial intensity distributions due to the neglect of the forward-backward asymmetry of the angular photoelectron distribution.

  18. Modeling and parameterization of photoelectrons emitted in condensed matter by linearly polarized synchrotron radiation

    Science.gov (United States)

    Jablonski, A.

    2018-01-01

    Growing availability of synchrotron facilities stimulates an interest in quantitative applications of hard X-ray photoemission spectroscopy (HAXPES) using linearly polarized radiation. An advantage of this approach is the possibility of continuous variation of radiation energy that makes it possible to control the sampling depth for a measurement. Quantitative applications are based on accurate and reliable theory relating the measured spectral features to needed characteristics of the surface region of solids. A major complication in the case of polarized radiation is an involved structure of the photoemission cross-section for hard X-rays. In the present work, details of the relevant formalism are described and algorithms implementing this formalism for different experimental configurations are proposed. The photoelectron signal intensity may be considerably affected by variation in the positioning of the polarization vector with respect to the surface plane. This information is critical for any quantitative application of HAXPES by polarized X-rays. Different quantitative applications based on photoelectrons with energies up to 10 keV are considered here: (i) determination of surface composition, (ii) estimation of sampling depth, and (iii) measurements of an overlayer thickness. Parameters facilitating these applications (mean escape depths, information depths, effective attenuation lengths) were calculated for a number of photoelectron lines in four elemental solids (Si, Cu, Ag and Au) in different experimental configurations and locations of the polarization vector. One of the considered configurations, with polarization vector located in a plane perpendicular to the surface, was recommended for quantitative applications of HAXPES. In this configurations, it was found that the considered parameters vary weakly in the range of photoelectron emission angles from normal emission to about 50° with respect to the surface normal. The averaged values of the mean

  19. Diffraction limited focusing with controllable arbitrary three-dimensional polarization

    International Nuclear Information System (INIS)

    Chen, Weibin; Zhan, Qiwen

    2010-01-01

    We propose a new approach that enables full control over the three-dimensional state of polarization and the field distribution near the focus of a high numerical aperture objective lens. By combining the electric dipole radiation and a vectorial diffraction method, the input field at the pupil plane for generating arbitrary three-dimensionally oriented linear polarization at the focal point with a diffraction limited spot size is found analytically by solving the inverse problem. Arbitrary three-dimensional elliptical polarization can be obtained by introducing a second electric dipole oriented in the orthogonal plane with appropriate amplitude and phase differences

  20. A hemispherical photoelectron spectrometer with 2-dimensional delay-line detector and integrated spin-polarization analysis

    International Nuclear Information System (INIS)

    Plucinski, L.; Oelsner, A.; Matthes, F.; Schneider, C.M.

    2010-01-01

    Photoelectron spectrometers usually allow detection of either spin-resolved energy-distribution curves (EDCs) at single emission angle, or 2D angle-vs.-energy images without spin-resolution. We have combined the two detection schemes into one spectrometer system which permits simultaneous detection of a 1D spin-resolved EDC and a 2D angular map. A state-of-the-art hemispherical analyzer is used as an energy filter. Its original scintillator detector has been replaced by a delay-line-detector (DLD), and part of the electron beam is allowed to pass through to reach the spin-polarized low energy electron diffraction (SPLEED) spin-detector mounted subsequently. The electron-optics between DLD and SPLEED contains a 90 o deflector to feature simultaneous detection of in-plane and out-of-plane spin components. These electron-optics have been optimized for high transmission to reduce acquisition times in the spin-resolved mode.

  1. Characterizing edge and stacking structures of exfoliated graphene by photoelectron diffraction

    International Nuclear Information System (INIS)

    Matsui, Fumihiko; Ishii, Ryo; Matsuda, Hiroyuki; Morita, Makoto; Kitagawa, Satoshi; Koh, Shinji; Daimon, Hiroshi; Matsushita, Tomohiro

    2013-01-01

    The two-dimensional C 1s photoelectron intensity angular distributions (PIADs) and spectra of exfoliated graphene flakes and crystalline graphite were measured using a focused soft X-ray beam. Suitable graphene samples were selected by thickness characterization using Raman spectromicroscopy after transferring mechanically exfoliated graphene flakes onto a 90-nm-thick SiO 2 film. In every PIAD, a Kagomé interference pattern was observed, particularly clearly in the monolayer graphene PIAD. Its origin is the overlap of the diffraction rings formed by an in-plane C-C bond honeycomb lattice. Thus, the crystal orientation of each sample can be determined. In the case of bilayer graphene, PIAD was threefold-symmetric, while those of monolayer graphene and crystalline graphite were sixfold-symmetric. This is due to the stacking structure of bilayer graphene. From comparisons with the multiple scattering PIAD simulation results, the way of layer stacking as well as the termination types in the edge regions of bilayer graphene flakes were determined. Furthermore, two different C 1s core levels corresponding to the top and bottom layers of bilayer graphene were identified. A chemical shift to a higher binding energy by 0.25 eV for the bottom layer was attributed to interfacial interactions. (author)

  2. Normal emission photoelectron diffraction: a new technique for determining surface structure

    International Nuclear Information System (INIS)

    Kevan, S.D.

    1980-05-01

    One technique, photoelectron diffraction (PhD) is characterized. It has some promise in surmounting some of the problems of LEED. In PhD, the differential (angle-resolved) photoemission cross-section of a core level localized on an adsorbate atom is measured as a function of some final state parameter. The photoemission final state consists of two components, one of which propagates directly to the detector and another which scatters off the surface and then propagates to the detector. These are added coherently, and interference between the two manifests itself as cross-section oscillations which are sensitive to the local structure around the absorbing atom. We have shown that PhD deals effectively with two- and probably also three-dimensionally disordered systems. Its non-damaging and localized, atom-specific nature gives PhD a good deal of promise in dealing with molecular overlayer systems. It is concluded that while PhD will never replace LEED, it may provide useful, complementary and possibly also more accurate surface structural information

  3. Sensitivity of photoelectron diffraction to conformational changes of adsorbed molecules: Tetra-tert-butyl-azobenzene/Au(111

    Directory of Open Access Journals (Sweden)

    A. Schuler

    2017-01-01

    Full Text Available Electron diffraction is a standard tool to investigate the atomic structure of surfaces, interfaces, and adsorbate systems. In particular, photoelectron diffraction is a promising candidate for real-time studies of structural dynamics combining the ultimate time resolution of optical pulses and the high scattering cross-sections for electrons. In view of future time-resolved experiments from molecular layers, we studied the sensitivity of photoelectron diffraction to conformational changes of only a small fraction of molecules in a monolayer adsorbed on a metallic substrate. 3,3′,5,5′-tetra-tert-butyl-azobenzene served as test case. This molecule can be switched between two isomers, trans and cis, by absorption of ultraviolet light. X-ray photoelectron diffraction patterns were recorded from tetra-tert-butyl-azobenzene/Au(111 in thermal equilibrium at room temperature and compared to patterns taken in the photostationary state obtained by exposing the surface to radiation from a high-intensity helium discharge lamp. Difference patterns were simulated by means of multiple-scattering calculations, which allowed us to determine the fraction of molecules that underwent isomerization.

  4. Control of the spin polarization of photoelectrons/photoions using short laser pulses

    International Nuclear Information System (INIS)

    Nakajima, Takashi

    2004-01-01

    We present a generic pump-probe scheme to control spin polarization of photoelectrons/photoions by short laser pulses. By coherently exciting fine structure manifolds of a multi-valence-electron system by the pump laser, a superposition of fine structure states is created. Since each fine structure state can be further decomposed into a superposition of various spin states of valence electrons, each spin component evolves differently in time. This means that varying the time delay between the pump and probe lasers leads to the control of spin states. Specific theoretical results are presented for two-valence-electron atoms, in particular for Mg, which demonstrate that not only the degree of spin polarization but also its sign can be manipulated through time delay. Since the underline physics is rather general and transparent, the presented idea may be potentially applied to nanostructures such as quantum wells and quantum dots

  5. Intense Vibronic Modulation of the Chiral Photoelectron Angular Distribution Generated by Photoionization of Limonene Enantiomers with Circularly Polarized Synchrotron Radiation.

    Science.gov (United States)

    Rafiee Fanood, Mohammad M; Ganjitabar, Hassan; Garcia, Gustavo A; Nahon, Laurent; Turchini, Stefano; Powis, Ivan

    2018-04-17

    Photoionization of the chiral monoterpene limonene has been investigated using polarized synchrotron radiation between the adiabatic ionization threshold, 8.505 and 23.5 eV. A rich vibrational structure is seen in the threshold photoelectron spectrum and is interpreted using a variety of computational methods. The corresponding photoelectron circular dichroism-measured in the photoelectron angular distribution as a forward-backward asymmetry with respect to the photon direction-was found to be strongly dependent on the vibronic structure appearing in the photoelectron spectra, with the observed asymmetry even switching direction in between the major vibrational peaks. This effect can be ultimately attributed to the sensitivity of this dichroism to small phase shifts between adjacent partial waves of the outgoing photoelectron. These observations have implications for potential applications of this chiroptical technique, where the enantioselective analysis of monoterpene components is of particular interest. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Adsorption of thiophene on a Si(0 0 1)-2 x 1 surface studied by photoelectron spectroscopy and diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Shimomura, M. [Research Institute of Electronics, Shizuoka University, Johoku, Hamamatsu 432-8011 (Japan)]. E-mail: romshimo@rie.shizuoka.ac.jp; Ikejima, Y. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yajima, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yagi, T. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan); Goto, T. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan); Gunnella, R. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan); UdR INFM, Department of Physics, University of Camerino, Camerino 62032 (Italy); Abukawa, T. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan); Fukuda, Y. [Research Institute of Electronics, Shizuoka University, Johoku, Hamamatsu 432-8011 (Japan); Kono, S. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2004-10-15

    Chemisorption of thiophene on a Si(0 0 1) surface has been studied by synchrotron radiation induced photoelectron spectroscopy (SRPES). Two adsorption-related components in Si 2p and S 2p spectra are observed after exposure of thiophene. It is suggested that the two components of Si 2p are ascribed to silicon bonded to hydrocarbon and sulfur. The core-level shift resolved photoelectron diffraction (PED) result indicates that the low-kinetic-energy component of S 2p can be ascribed to 2,5-dihydrothiophehe (DHT)-like species. Another S 2p component could be assigned to dissociated sulfur based on the results of PED and time evolution of the spectrum under irradiation. These assignments are consistent with the core-level shift of S 2p.

  7. Adsorption of thiophene on a Si(0 0 1)-2 x 1 surface studied by photoelectron spectroscopy and diffraction

    International Nuclear Information System (INIS)

    Shimomura, M.; Ikejima, Y.; Yajima, K.; Yagi, T.; Goto, T.; Gunnella, R.; Abukawa, T.; Fukuda, Y.; Kono, S.

    2004-01-01

    Chemisorption of thiophene on a Si(0 0 1) surface has been studied by synchrotron radiation induced photoelectron spectroscopy (SRPES). Two adsorption-related components in Si 2p and S 2p spectra are observed after exposure of thiophene. It is suggested that the two components of Si 2p are ascribed to silicon bonded to hydrocarbon and sulfur. The core-level shift resolved photoelectron diffraction (PED) result indicates that the low-kinetic-energy component of S 2p can be ascribed to 2,5-dihydrothiophehe (DHT)-like species. Another S 2p component could be assigned to dissociated sulfur based on the results of PED and time evolution of the spectrum under irradiation. These assignments are consistent with the core-level shift of S 2p

  8. Photoelectron spectroscopy principles and applications

    CERN Document Server

    Hüfner, Stefan

    1995-01-01

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

  9. Structure determination of Ga As (110) p (1 x 1) - Sb using scanned-energy photoelectron diffraction

    International Nuclear Information System (INIS)

    Ascolani, H.; Asensio, M.C.; Fritzsche, W.

    1996-01-01

    Photoelectron diffraction (PD) in the scanned-energy mode has proven to be a powerfull tool for structural determination of the first few surface layers. The scanned-energy mode involves the measurement of the intensity of photoelectrons emitted from a core level as a function of the incident photon energy for different emission directions. The atom specificity of PD allows the investigation of the local structure of adsorbed atoms without interference of the substrate. In addition, if a measurable chemical shift exists, this technique is also able to discriminate between atoms of the same species adsorbed in inequivalent sites. The Ga As (110) p (1x1)-Sb (1 ML) surface represents a prototype system to study atom adsorption on III-V semiconductors. The epitaxial continued layer structure (ECLS) is generally accepted as the geometry corresponding to this surface, although some authors have claimed that the p 3 model forms a stable geometry equivalent to the ECLS, and that it provides an equally good description of their experimental results. So far, the conclusions about the atomic structure of this surface had been derived on the basis of indirect methods. This work exploits to the utmost the possibilities of analysis offered by the scanned-energy PD technique, namely, chemical shift analysis and direct inversion. The energy spectrum of Sb-4d photoelectrons emitted from the Ga As (110)-p (1x1) Sb surface has two chemically-shifted components. We have inverted the scanned-energy photoelectron diffraction data corresponding to these two components to obtain the positions of the Ga and As atoms which are nearest neighbors of two inequivalent Sb atoms. Our results contradict various models proposed for this surface and are consistent only with the ECLS. For a more detailed atomic structure determination, the best fit between experiment and multiple-scattering calculations was determined by a trial-and-error procedure. (author)

  10. Structure of the c(2x2) Mn/Ni(001) surface alloy by quantitative photoelectron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, S.; Denlinger, J.; Chen, X. [Univ. of Wisconsin, Milwaukee, WI (United States)] [and others

    1997-04-01

    Surface alloys are two-dimensional metallic systems that can have structures that are unique to the surface, and have no counterpart in the bulk binary phase diagram. A very unusual structure was reported for the Mn-Ni system, based on a quantitative LEED structure determination, which showed that the Mn atoms were displaced out of the surface by a substantial amount. This displacement was attributed to a large magnetic moment on the Mn atoms. The structure of the Mn-Ni surface alloy was proposed to be based on a bulk termination model. Magnetic measurements on the Mn-Ni surface alloys, however, showed conclusively that the magnetic structure of these surface alloys is completely different from the bulk alloy analogs. For example, bulk MnNi is an antiferromagnet, whereas the surface alloy is ferromagnetic. This suggests that the proposed structure based on bulk termination, may not be correct. X-ray Photoelectron Diffraction (XPD) techniques were used to investigate this structure, using both a comparison to multiple scattering calculations and photoelectron holography. In this article the authors present some of the results from the quantitative analysis of individual diffraction patterns by comparison to theory.

  11. Counterintuitive angular shifts in the photoelectron momentum distribution for atoms in strong few-cycle circularly polarized laser pulses

    DEFF Research Database (Denmark)

    Martiny, Christian; Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2009-01-01

    We solve the three-dimensional time-dependent Schrödinger equation for a three-cycle circularly polarized laser pulse interacting with an atom. The photoelectron momentum distributions show counterintuitive shifts, similar to those observed in a recent experiment (Eckle et al 2008 Science 322 1525...

  12. X-ray photoelectron spectroscopy, high-resolution X-ray diffraction ...

    Indian Academy of Sciences (India)

    the crystalline quality through full-width at half-maximum values. .... angular divergence of ∆α = 12 arc sec. X-rays generated from the monochromator were diffracted from (0 0 6) LiNbO3 atomic planes with the (+, −, −, +, +) geometry. [8].

  13. Photoelectron diffraction from single oriented molecules: Towards ultrafast structure determination of molecules using x-ray free-electron lasers

    Science.gov (United States)

    Kazama, Misato; Fujikawa, Takashi; Kishimoto, Naoki; Mizuno, Tomoya; Adachi, Jun-ichi; Yagishita, Akira

    2013-06-01

    We provide a molecular structure determination method, based on multiple-scattering x-ray photoelectron diffraction (XPD) calculations. This method is applied to our XPD data on several molecules having different equilibrium geometries. Then it is confirmed that, by our method, bond lengths and bond angles can be determined with a resolution of less than 0.1 Å and 10∘, respectively. Differently from any other scenario of ultrafast structure determination, we measure the two- or three-dimensional XPD of aligned or oriented molecules in the energy range from 100 to 200 eV with a 4π detection velocity map imaging spectrometer. Thanks to the intense and ultrashort pulse properties of x-ray free-electron lasers, our approach exhibits the most probable method for obtaining ultrafast real-time structural information on small to medium-sized molecules consisting of light elements, i.e., a “molecular movie.”

  14. Non-dipole effects in spin polarization of photoelectrons from 3d electrons of Xe, Cs and Ba

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Cherepkov, N A [State University of Aerospace Instrumentation, St. Petersburg 190000 (Russian Federation); Chernysheva, L V [A F Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Felfli, Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta GA 30314 (United States); Msezane, A Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta GA 30314 (United States)

    2005-04-28

    The non-dipole contribution to spin polarization of photoelectrons from Xe, Cs and Ba 3d{sub 5/2} and 3d{sub 3/2} levels is calculated. The calculation is carried out within the framework of a modified version of the spin-polarized random phase approximation with exchange. The effects of relaxation of excited electrons due to the 3d-vacancy creation are also accounted for. It is demonstrated that the parameters that characterize the photoelectron angular distribution as functions of the incoming photon energy, although being predictably small, acquire additional peculiarities when the interaction between electrons that belong to the 3d{sub 5/2} and 3d{sub 3/2} components of the spin-orbit doublet is taken into account.

  15. Polarization-dependent diffraction in all-dielectric, twisted-band structures

    Energy Technology Data Exchange (ETDEWEB)

    Kardaś, Tomasz M.; Jagodnicka, Anna; Wasylczyk, Piotr, E-mail: pwasylcz@fuw.edu.pl [Photonic Nanostructure Facility, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland)

    2015-11-23

    We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.

  16. Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction

    Science.gov (United States)

    Ono, Hiroshi; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

    2014-03-01

    The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.

  17. Stereo photograph of atomic arrangement by circularly-polarized-light two-dimensional photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Daimon, Hiroshi

    2003-01-01

    A stereo photograph of atomic arrangement was obtained for the first time. The stereo photograph was displayed directly on the screen of display-type spherical-mirror analyzer without any computer-aided conversion process. This stereo photography was realized taking advantage of the phenomenon of circular dichroism in photoelectron angular distribution due to the reversal of orbital angular momentum of photoelectrons. The azimuthal shifts of forward focusing peaks in a photoelectron angular distribution pattern taken with left and right helicity light in a special arrangement are the same as the parallaxes in a stereo view of atoms. Hence a stereoscopic recognition of three-dimensional atomic arrangement is possible, when the left eye and the right eye respectively view the two images obtained by left and right helicity light simultaneously. (author)

  18. The structure of formate on TiO{sub 2}(110) by scanned-energy and scanned-angle photoelectron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Thevuthasan, S.; Kim, Y.J.; Herman, G.S. [Pacific Northwest National Laboratory, Richland, WA (United States)] [and others

    1997-04-01

    There is a considerable interest in understanding the interaction of small organic molecules with oxide surfaces. The chemistry of formate interactions with TiO{sub 2}(110) has been investigated by several groups, but there is little information on the structure of the adsorbate/surface complex. Recently the authors combined high-energy x-ray photoelectron diffraction (XPD) measurements at PNNL with low-energy scanned-angle and scanned-energy photoelectron diffraction measurements at the ALS to investigate the structure of the formate ion on TiO{sub 2}(110) in detail. The high-energy XPD results reveal that formate binds through the oxygens in a bidentate fashion to Ti cation rows along the [001] direction with an O-C-O bond angle of about 126{degrees}. Low-energy photoelectron diffraction data, which is briefly described below, was used to identify the specific bonding geometry, including the bond length between the Ti cation and the oxygen in the formate.

  19. Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

    Energy Technology Data Exchange (ETDEWEB)

    Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburg, PA (United States); Dickey, Elizabeth C. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States)

    2017-02-15

    A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO{sub 3} single crystals. Further, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system. - Highlights: • A novel technique to directly polar domains utilizing EBSD is demonstrated. • The technique relies on dynamical diffraction simulations of EBSD patterns. • The technique is demonstrated by mapping 180° domains in LiNbO{sub 3} single crystals. • Further application of this technique to other materials classes is discussed.

  20. Modifications to 8x8 dynamical theory: Polarizations redefined according to x-ray diffraction convention

    International Nuclear Information System (INIS)

    Macrander, A.T.; Blasdell, R.C.

    1993-09-01

    Dynamical x-ray diffraction theory can be cast in matrix form. In recent years, an 8x8 matrix theory was developed that treated asymmetric reflections from strained crystals. The polarization of the incident, specularly reflected, reflected diffracted, transmitted diffracted, and transmitted electromagnetic wave fields were all defined as s or p. That is, polarizations were defined with respect to the plane containing the incident beam direction and the surface normal. The authors present modifications of the theory to treat σ and π polarizations for Bragg diffraction from asymmetric planes, that is, for polarizations defined with respect to the plane containing the incident beam direction and the reciprocal lattice vector for Bragg diffraction. They present results of this theory for unstrained crystals in the inclined geometry. In this geometry the incident beam wavevector, the reciprocal lattice vector, and the surface normal are not coplanar. The inclined crystal geometry appears promising for use in a high-heat-load monochromator for undulator radiation at the Advanced Photon Source. As expected, they find a weak π-polarization component in the diffracted beam when the polarization of the incident beam is pure σ

  1. Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Terry, J.; Linford, M.R.; Wigren, C.; Cao, R.; Pianetta, P.; Chidsey, C.E. [Stanford University, Stanford, California 94309 (United States)

    1997-08-01

    The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H{endash}Si bond on the H{endash}Si(111) surface, and (ii) replacement of Cl on the Cl{endash}Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C 1s signal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C{endash}Si bond length of 1.85{plus_minus}0.05{Angstrom}. Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. {copyright} {ital 1997 American Institute of Physics.}

  2. Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction

    International Nuclear Information System (INIS)

    Terry, J.; Linford, M.R.; Wigren, C.; Cao, R.; Pianetta, P.; Chidsey, C.E.

    1997-01-01

    The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H endash Si bond on the H endash Si(111) surface, and (ii) replacement of Cl on the Cl endash Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C 1s signal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C endash Si bond length of 1.85±0.05 Angstrom. Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. copyright 1997 American Institute of Physics

  3. Polarized neutron powder diffraction studies of antiferromagnetic order in bulk and nanoparticle NiO

    DEFF Research Database (Denmark)

    Brok, Erik; Lefmann, Kim; Deen, Pascale P.

    2015-01-01

    surface contribution to the magnetic anisotropy. Here we explore the potential use of polarized neutron diffraction to reveal the magnetic structure in NiO bulk and nanoparticle powders by applying the XYZ-polarization analysis method. Our investigations address in particular the spin orientation in bulk....... The results show that polarization analyzed neutron powder diffraction is a viable method to investigate magnetic order in powders of antiferromagnetic nanoparticles.......In many materials it remains a challenge to reveal the nature of magnetic correlations, including antiferromagnetism and spin disorder. Revealing the spin structure in magnetic nanoparticles is further complicated by the large incoherent neutron scattering cross section from water adsorbed...

  4. A three-dimensional polarization domain retrieval method from electron diffraction data

    International Nuclear Information System (INIS)

    Pennington, Robert S.; Koch, Christoph T.

    2015-01-01

    We present an algorithm for retrieving three-dimensional domains of picometer-scale shifts in atomic positions from electron diffraction data, and apply it to simulations of ferroelectric polarization in BaTiO 3 . Our algorithm successfully and correctly retrieves polarization domains in which the Ti atom positions differ by less than 3 pm (0.4% of the unit cell diagonal distance) with 5 and 10 nm depth resolution along the beam direction, and we also retrieve unit cell strain, corresponding to tetragonal-to-cubic unit cell distortions, for 10 nm domains. Experimental applicability is also discussed. - Highlights: • We show a retrieval method for ferroelectric polarization from TEM diffraction data. • Simulated strain and polarization variations along the beam direction are retrieved. • This method can be used for 3D strain and polarization mapping without specimen tilt

  5. Photoelectron Diffraction Imaging for C2H2 and C2H4 Chemisorbed on Si(100) Reveals a New Bonding Configuration

    International Nuclear Information System (INIS)

    Xu, S. H.; Keeffe, M.; Yang, Y.; Chen, C.; Yu, M.; Lapeyre, G. J.; Rotenberg, E.; Denlinger, J.; Yates, J. T. Jr.

    2000-01-01

    A new adsorption site for adsorbed acetylene on Si(100) is observed by photoelectron imaging based on the holographic principle. The diffraction effects in the carbon 1s angle-resolved photoemission are inverted (including the small-cone method) to obtain an image of the atom's neighboring carbon. The chemisorbed acetylene molecule is bonded to four silicon surface atoms. In contrast to the C 2 H 2 case, the image for adsorbed C 2 H 4 shows it bonded to two Si surface atoms. (c) 2000 The American Physical Society

  6. Further development in theory/data closure of the photoelectron-driven polar wind and day-night transition of the outflow

    Directory of Open Access Journals (Sweden)

    S. W. Y. Tam

    Full Text Available Recent in situ observations have revealed novel features in the polar wind. Measurements between 5000 and 9000 km altitude by the Akebono satellite indicate that both H+ and O+ ions can have remarkably higher outflow velocities in the sunlit region than on the nightside. Electrons also display an asymmetric behavior: the dayside difference in energy spread, greater for upward-moving than downward-moving electrons, is absent on the nightside. Here, we discuss the further development of a theory by Tam et al. that can explain most of these observed peculiar properties by properly taking into account the global, kinetic, collisional effects of the sunlit photoelectrons, on the background polar wind and the electric field. Quantitative comparisons of the calculated results with actual data will be described. In addition, transition from the daytime photoelectron-driven polar wind to the night-time polar wind will be discussed.

  7. Determination of electronic and atomic properties of surface, bulk and buried interfaces: Simultaneous combination of hard X-ray photoelectron spectroscopy and X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Zuazo, J., E-mail: rubio@esrf.fr [SpLine, Spanish CRG BM25 Beamline at the ESRF, ESRF, B.P. 220, F-38043 Grenoble (France); Instituto de Ciencia de Materiales de Madrid, ICMM, CSIC, Cantoblanco, E-28049 Madrid (Spain); Castro, G.R. [SpLine, Spanish CRG BM25 Beamline at the ESRF, ESRF, B.P. 220, F-38043 Grenoble (France); Instituto de Ciencia de Materiales de Madrid, ICMM, CSIC, Cantoblanco, E-28049 Madrid (Spain)

    2013-10-15

    Highlights: •We have developed a novel and exceptional tool for non-destructive characterization of bulk and buried interfaces that combine XRD and HAXPES. •We studied the correlation between the atomic, electronic and transport properties of oxygen deficient manganite thin films. •The diffraction data showed a cooperative tilt of the MnO{sub 6} block along the out-of-plane direction. •We shown the absence of the conventional basal plane rotation for the oxygen deficient samples. -- Abstract: Hard X-ray photoelectron spectroscopy (HAXPES) is a powerful novel emerging technique for bulk compositional, chemical and electronic properties determination in a non-destructive way. It benefits from the exceptionally large escape depth of high kinetic energy photoelectrons enabling the study of bulk and buried interfaces up to several tens of nanometres depth. Its advantage over conventional XPS is based on the long mean free path of high kinetic energetic photoelectrons. Using the advantage of tuneable X-ray radiation provided by synchrotron sources the photoelectron kinetic energy, i.e. the information depth can be changed and consequently electronic and compositional depth profiles can be obtained. The combination of HAXPES with an atomic structure sensitive technique, as X-ray diffraction, opens a new research field with great potential for many systems in which their electronic properties are intimately linked to their crystallographic structure. At SpLine, the Spanish CRG Beamline at the European Synchrotron Radiation Facility (ESRF) we have developed a novel and exceptional set-up that combine grazing incidence X-ray diffraction (GIXRD) and HAXPES. Both techniques can be operated simultaneously on the same sample and using the same excitation source. The set-up includes a heavy 2S+3D diffractometer and UHV chamber equipped with an electrostatic analyzer. The UHV chamber has also MBE evaporation sources, an ion gun, a LEED optic, a sample heating and cooling

  8. Polarization control of non-diffractive helical optical beams through subwavelength metallic apertures

    International Nuclear Information System (INIS)

    Lombard, E; Genet, C; Ebbesen, T W; Drezet, A

    2010-01-01

    We demonstrate experimentally a simple method for preparing non-diffractive vectorial optical beams that can display wave-front helicity. This method is based on space-variant modifications of the polarization of an optical beam transmitted through subwavelength annular rings perforating opaque metal films. We show how the description of the optical properties of such structures must account for the vectorial character of the polarization and how, in turn, these properties can be controlled by straightforward sequences of preparation and analysis of polarization states.

  9. High diffraction efficiency polarization gratings recorded by biphotonic holography in an azobenzene liquid crystalline polyester

    DEFF Research Database (Denmark)

    Sánchez, C; Alcalá, R; Hvilsted, Søren

    2001-01-01

    High diffraction efficiencies have been achieved with polarization gratings recorded in thin films of an azobenzene side-chain liquid crystalline polyester by means of biphotonic processes. Efficiency values up to 30% have been reached after an induction period of 300 s and subsequent evolution...

  10. Anomalous spin distribution in the superconducting ferromagnet UCoGe studied by polarized neutron diffraction

    NARCIS (Netherlands)

    Prokeš, K.; de Visser, A.; Huang, Y.K.; Fåk, B.; Ressouche, E.

    2010-01-01

    We report a polarized neutron-diffraction study conducted to reveal the nature of the weak ferromagnetic moment in the superconducting ferromagnet UCoGe. We find that the ordered moment in the normal phase in low magnetic fields (B∥c) is predominantly located at the U atom and has a magnitude of

  11. Diffraction from polarization holographic gratings with surface relief in side-chain azobenzene polyesters

    DEFF Research Database (Denmark)

    Naydenova, I; Nikolova, L; Todorov, T

    1998-01-01

    We investigate the polarization properties of holographic gratings in side-chain azobenzene polyesters in which an anisotropic grating that is due to photoinduced linear and circular birefringence is recorded in the volume of the material and a relief grating appears on the surface. A theoretical...... model is proposed to explain the experimental results, making it possible to understand the influence of the different photoinduced effects. It is shown that at low intensity the polarization properties of the diffraction at these gratings are determined by the interaction of the linear and circular...... photobirefringences, and at larger intensity the influence of the surface relief dominates the effect of the circular anisotropy. Owing to the high recording efficiency of the polyesters, the +/-1-order diffracted waves change the polarization interference pattern during the holographic recording, resulting...

  12. Characterization of sintered samples of La/Sr/Cu/O by X-ray diffraction, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS)

    International Nuclear Information System (INIS)

    Gonzalez, C.O. de; Polla, Griselda; Manghi, Estela

    1987-01-01

    Samples of La/Sr/Cu/O were sinterized by solid state reaction starting from a nominal composition of La 1 .8, Sr 0 .2, CuO 4 . They presented superconductive properties with T c = 40.9 K (onset) and δ T c = 17 K. Two phases were observed by X-ray diffraction and the more abundant was the tetragonal phase. The mean grain size was 1-5 μm. The X-ray photoelectron spectroscopy measurements were carried out using Mg kα (1486.6 eV) as incident radiation. Sample temperature was varied between -180 deg C and 420 deg C, approximately. The temperature variation produces a change in the atomic concentration of the surface components. Deconvolutions of the O 1s peaks show three components with binding energies (B.E.). The decomposition of Cu 2p 3 /2 peaks presents two components corresponding to Cu + and Cu 2+ . (Author) [es

  13. Photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Price, W.C.

    1974-01-01

    A survey is given of the development of x-ray and ultraviolet photoelectron spectroscopy. Applications of photoelectron spectroscopy to studies of atomic electronic configurations are discussed, including photoelectron spectra of hydrides isoelectronic with the inert gases; photoelectron spectra of the halogen derivatives of methane; photoelectron spectra of multiple bonded diatomic molecules; spectra and structure of some multiple bonded polyatomic molecules; spectra and structure of triatomic molecules; and methods of orbital assignment of bands in photoelectron spectra. Physical aspects are considered, including intensities; selection rules; dependence of cross section on photoelectron energy; autoionization; angular distribution of photoelectrons; electron-molecule interactions; and transient species. (26 figures, 54 references) (U.S.)

  14. Polarization of protons produced in diffractive disintegration of deuterons by high-energy pions

    International Nuclear Information System (INIS)

    Gakh, G.Yi.; Rekalo, M.P.

    1996-01-01

    For the process of diffractive disintegration of unpolarized deuterons by the high-energy pions, π + d → π + p + n, the polarization characteristics of produced protons are calculated. Using the vector nature of the Pomeron exchange, the general structure of all components of proton polarization vector is found for d (π, π p) n. By the Pomeron-photon analogy, the amplitude of the process P + d → n + p is approximated by the isoscalar contribution of four Born diagrams similar to the case of deuteron electrodisintegration. Unitarization of the amplitude is achieved by introducing in multipole amplitudes the corresponding phases of np-scattering. The numerical calculation of all components of the polarization vector of protons, produced in the case of noncomplanar kinematics of the reaction π + d → π + p + n, is realized

  15. Investigation of TbMn2O5 by polarized neutron diffraction.

    Science.gov (United States)

    Zobkalo, I A; Gavrilov, S V; Sazonov, A; Hutanu, V

    2018-05-23

    In order to make a new approach to the elucidation of the microscopic mechanisms of multiferroicity in the RMn 2 O 5 family, experiments with different methods of polarized neutrons scattering were performed on a TbMn 2 O 5 single crystal. We employed three different techniques of polarized neutron diffraction without the analysis after scattering, the XYZ-polarization analysis, and technique of spherical neutron polarimetry (SNP). Measurements with SNP were undertaken both with and without external electric field. A characteristic difference in the population of 'right' and 'left' helix domains in all magnetically ordered phases of TbMn 2 O 5 , was observed. This difference can be controlled by an external electric field in the field-cooled mode. The analysis of the results gives an evidence that antisymmetric Dzyaloshinsky-Moria exchange is effective in all the magnetic phases in TbMn 2 O 5 .

  16. Polarized neutron diffraction - a tool for testing extinction models: application to yttrium iron garnet

    International Nuclear Information System (INIS)

    Bonnet, M.; Delapalme, A.; Becker, P.

    1976-01-01

    This paper shows that polarized neutron experiments, which do not depend on any scale factor, are very dependent on extinction and provide original tests for extinction models. Moon, Koehler, Cable and Child (1972) have formulated the problem and proposed a first-order solution applicable only when the extinction is small. In the first part, some analytical derivations of secondary extinction corrections are discussed, using the formalism of Becker and Coppens (1974). In the second part, the main principles governing polarized neutron diffraction are briefly reviewed, with a special discussion of extinction problems. The method is then applied to the case of yttrium iron garnet (YIG). This experiment shows the technique of polarized neutrons to be very powerful for testing extinction models and for deciding whether the crystal behaves dynamically or kinematically (following Kato's criterion). (Auth.)

  17. Investigation of TbMn2O5 by polarized neutron diffraction

    Science.gov (United States)

    Zobkalo, I. A.; Gavrilov, S. V.; Sazonov, A.; Hutanu, V.

    2018-05-01

    In order to make a new approach to the elucidation of the microscopic mechanisms of multiferroicity in the RMn2O5 family, experiments with different methods of polarized neutrons scattering were performed on a TbMn2O5 single crystal. We employed three different techniques of polarized neutron diffraction without the analysis after scattering, the XYZ-polarization analysis, and technique of spherical neutron polarimetry (SNP). Measurements with SNP were undertaken both with and without external electric field. A characteristic difference in the population of ‘right’ and ‘left’ helix domains in all magnetically ordered phases of TbMn2O5, was observed. This difference can be controlled by an external electric field in the field-cooled mode. The analysis of the results gives an evidence that antisymmetric Dzyaloshinsky-Moria exchange is effective in all the magnetic phases in TbMn2O5.

  18. Vibrationally induced inversion of photoelectron forward-backward asymmetry in chiral molecule photoionization by circularly polarized light

    Science.gov (United States)

    Garcia, Gustavo A.; Nahon, Laurent; Daly, Steven; Powis, Ivan

    2013-01-01

    Electron–nuclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck–Condon assumption, ascribed to the enhanced sensitivity of photoelectron circular dichroism (compared with other observables like cross-sections or the conventional anisotropy parameter-β) to the scattering phase off the chiral molecular potential, inducing a dependence on the nuclear geometry sampled in the photoionization process. Important consequences for the interpretation of such dichroism measurements within analytical contexts are discussed. PMID:23828557

  19. Atomic structure determination of InSb(100)c(4x4) and c(8x2)phases by X-ray photoelectron diffraction

    International Nuclear Information System (INIS)

    Carvalho, V.E. de; Soares, E.A.; Magalhaes, M.R.P.; Paniago, R.; Siervo, A. de; Landers, R.

    2004-01-01

    Full text: The (100) surfaces of III-V compound semiconductors exhibit a variety of surface reconstructions that have attracted a lot of attention because of their importance in both homo epitaxial and heteroepitaxial growth. In the special case of the narrow bandgap InSb compound semiconductor its potential application in high-speed electronic and optoelectronic devices has encourage many studies of its (100) surface atomic structure. Among the reconstructions presented by the InSb(100) surface two of them have received more attention, that is, the observed well-ordered In-rich c(8x2) and Sb terminated c(4x4) surfaces. The c(8x2) structure can be obtained by exposing the surface to low energy ion bombardment and annealing, whereas the c(4x4) structure involves the chemisorption of Sb onto an already Sb-terminated surface. These two structures have been studied mainly by scanning tunneling microscopy (STM) and surface X-ray diffraction (SXRD) techniques and all the proposed models are based on the occurrence of group III (and/or V) blocks of dimmers occupying sites on the top or at subsurface layer. However, there are still difficulties in determining either the exact number of atoms in each dimmer or the number of dimmers in each block. With the goal of getting a better structure determination of the InSb(100) surface phases a photoelectron diffraction experiment (XPD) was carried out at LNLS where synchrotron and Al-K α radiations have been used. In the present work, the experimental and preliminary results of structure determination for both In Sn(100)c(8x2) and InSb(100)c(4x4) phases will be presented and discussed. (author)

  20. Structural origin of Si-2p core-level shifts from Si(100)-c[4x2] surface: A spectral x-ray photoelectron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Chen, X.; Tonner, B.P. [Univ. of Wisconsin, Milwaukee, WI (United States); Denlinger, J. [Univ. of Wisconsin, Milwaukee, WI (United States)][Ernest Orlando Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors have performed angle-resolved x-ray photoelectron diffraction (XPD) from a Si(100)-c(4x2) surface to study the structural origin of Si-2p core-level shifts. In the experiment, the highly resolved surface Si-2p core-level spectra were measured as a fine grid of hemisphere and photon energies, using the SpectroMicroscopy Facility {open_quotes}ultraESCA{close_quotes} instrument. By carefully decomposing the spectra into several surface peaks, the authors are able to obtain surface-atom resolved XPD patterns. Using a multiple scattering analysis, they derived a detailed atomic model for the Si(100)-c(4x2) surface. In this model, the asymmetric dimers were found tilted by 11.5 plus/minus 2.0 degrees with bond length of 2.32 plus/minus 0.05{angstrom}. By matching model XPD patterns to experiment, the authors can identify which atoms in the reconstructed surface are responsible for specific photoemission lines in the 2p spectrum.

  1. Surface analysis using X-ray photoelectron spectroscopy and X-ray diffraction of UO2 fuel pellets oxidised in air at 2300C and 2700C

    International Nuclear Information System (INIS)

    Tempest, P.A.; Tyler, J.W.

    1987-08-01

    Factors which affect the UO 2 → U 3 O 8 transformation have been investigated by sequentially oxidising UO 2 fuel pellets in air at 230 0 C and 270 0 C and monitoring the growth of U 3 O 7 and U 3 O 8 using X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. Initially oxidation proceeded at a linear rate by the inward diffusion of oxygen to form a complete layer of sub-stoichiometric U 3 O 7 . This phase was tetragonal with a c/a ratio of 1.015, significantly less than the value of 1.03 measured on UO 2 powder when oxidised under identical conditions. This difference and the preferred orientation exhibited by surface grains were caused by growth stresses induced in the pellet surface. Both intergranular and transgranular cracking occurred and became nucleation sites for the growth of U 3 O 8 . The linear oxidation period associated with U 3 O 7 growth was much shorter at 270 0 C than 230 0 C and U 3 O 8 nucleated earlier. Spallation and the production of particulate were only observed during the formation of U 3 O 8 when a 30% increase in volume arose from the U 3 O 7 → U 3 O 8 phase change. (author)

  2. High diffraction efficiency polarization gratings recorded by biphotonic holography in an azobenzene liquid crystalline polyester

    International Nuclear Information System (INIS)

    Sanchez, C.; Alcala, R.; Hvilsted, S.; Ramanujam, P. S.

    2001-01-01

    High diffraction efficiencies have been achieved with polarization gratings recorded in thin films of an azobenzene side-chain liquid crystalline polyester by means of biphotonic processes. Efficiency values up to 30% have been reached after an induction period of 300 s and subsequent evolution with the sample in darkness. These values are at least two orders of magnitude higher than those previously reported for biphotonic recording. The gratings can be erased with unpolarized blue light and partial recovery of the diffraction efficiency has been observed after the erasure process when the sample is kept in darkness. Red light illumination of the erased film increases the recovered efficiency value and the recovery rate. [copyright] 2001 American Institute of Physics

  3. The structure of liquid water by polarized neutron diffraction and reverse Monte Carlo modelling.

    Science.gov (United States)

    Temleitner, László; Pusztai, László; Schweika, Werner

    2007-08-22

    The coherent static structure factor of water has been investigated by polarized neutron diffraction. Polarization analysis allows us to separate the huge incoherent scattering background from hydrogen and to obtain high quality data of the coherent scattering from four different mixtures of liquid H(2)O and D(2)O. The information obtained by the variation of the scattering contrast confines the configurational space of water and is used by the reverse Monte Carlo technique to model the total structure factors. Structural characteristics have been calculated directly from the resulting sets of particle coordinates. Consistency with existing partial pair correlation functions, derived without the application of polarized neutrons, was checked by incorporating them into our reverse Monte Carlo calculations. We also performed Monte Carlo simulations of a hard sphere system, which provides an accurate estimate of the information content of the measured data. It is shown that the present combination of polarized neutron scattering and reverse Monte Carlo structural modelling is a promising approach towards a detailed understanding of the microscopic structure of water.

  4. The Growth of Thin Epitaxial Copper Films on Ruthenium (0001)and Oxygen-Precovered Ruthenium (0001) as studied by X-ray Photoelectron diffraction

    International Nuclear Information System (INIS)

    Ruebush, Scott Daniel

    1997-01-01

    In the first part of this dissertation, the variation of mean emitter depths with direction for core photoelectron emission from single crystals, including the effects of both isotropic inelastic scattering and single and multiple elastic scattering was theoretically studied. The mean emitter depth was found to vary by as much as ±30% with direction. In the second part of this dissertation, x-ray photoelectron diffraction (XPD) was used to study the structure and growth mechanisms of Cu films grown on a clean and an oxygen-precovered Ru(OOO1) surface. Experimental Cu 2p3/2 (E kin = 556 eV) and Ru 3d (E kin = 1205 eV) intensities were measured for Cu coverages from submonolayer up to several monolayer (ML) on the clean Ru(OOO1) surface. In addition, the O 1s (E kin = 958 eV) intensity was measured for Cu grown on oxygen precovered Ru(OOO1). These XPD intensities have been analyzed using single scattering cluster (SSC) and multiple scattering cluster (MSC) models. The first Cu layer has been found to grow pseudomorphically on the Ru(OOO1) surface in agreement with prior studies of the Cu/Ru(OOO 1) system. Thus, the initial growth is layer-by-layer. For higher coverages, XPD shows that the short-range structure of the Cu films is fcc Cu(l 11), but with significant interlayer relaxation (compared to bulk Cu(l 11)) that persists up to ≥8 ML. When oxygen is preadsorbed on the Ru(OOO1) surface before Cu film growth (possibly to act as a surfactant promoting smoother growth), XPD shows that the first 3 ML of Cu grow as 3-D islands. In addition, XPD shows that, during Cu growth, all of the oxygen ''floats'' on the CU surface, in contrast to prior studies which found that 30% of the oxygen remains at the Cu/Ru intetiace. XPD also indicates that the oxygen is highly disordered on the Cu overlayer surface. In thicker layers with oxygen present, the Cu grows as Cu(l 11) with equal occupations of two possible domains rotated by 1800 from each other. In general, this work

  5. Photoelectron reflection and scattering at Venus: an upper limit on the "polar wind" ambipolar electric field, and a new source of top-side ionospheric heating

    Science.gov (United States)

    Collinson, Glyn; Glocer, Alex; Grebowsky, Joe; Peterson, William; Frahm, Rudy; Moore, Thomas; Gilbert, Lin; Coates, Andrew

    2015-04-01

    An important mechanism in the generation of Earth's polar wind is the ambipolar potential generated by the outflow along open field lines of superthermal electrons. This ≈20V electric potential assists ions in overcoming the gravitational potential, and is a key mechanism for Terrestrial ionospheric escape. At Venus, except in rare circumstances, every field line is open, and a similar outflow of ionospheric electrons is observed. It is thus hypothesized that a similar electric potential may be present at Venus, contributing to global ionospheric loss. However, a very sensitive electric field instrument would be required to directly measure this potential, and no such instrument has yet been flown to Venus. In this pilot study, we examine photoelectron spectra measured by the ASPERA-ELS instrument on the Venus Express to put an initial upper bound on the total potential drop above 350km of Φ current understanding, a "polar wind" like ambipolar electric field may not be as important a mechanism for atmospheric escape as previously suspected. Additionally, we find our spectra are consistent with the scattering of photoelectrons, the heating from which which we hypothesize may act as a source of top-side ionospheric heating, and may play a role in influencing the scale height of the ionosphere.

  6. Investigation on Surface Polarization of Al2O3-capped GaN/AlGaN/GaN Heterostructure by Angle-Resolved X-ray Photoelectron Spectroscopy.

    Science.gov (United States)

    Duan, Tian Li; Pan, Ji Sheng; Wang, Ning; Cheng, Kai; Yu, Hong Yu

    2017-08-17

    The surface polarization of Ga-face gallium nitride (GaN) (2 nm)/AlGaN (22 nm)/GaN channel (150 nm)/buffer/Si with Al 2 O 3 capping layer is investigated by angle-resolved X-ray photoelectron spectroscopy (ARXPS). It is found that the energy band varies from upward bending to downward bending in the interface region, which is believed to be corresponding to the polarization variation. An interfacial layer is formed between top GaN and Al 2 O 3 due to the occurrence of Ga-N bond break and Ga-O bond forming during Al 2 O 3 deposition via the atomic layer deposition (ALD). This interfacial layer is believed to eliminate the GaN polarization, thus reducing the polarization-induced negative charges. Furthermore, this interfacial layer plays a key role for the introduction of the positive charges which lead the energy band downward. Finally, a N 2 annealing at 400 °C is observed to enhance the interfacial layer growth thus increasing the density of positive charges.

  7. Characterization of as-grown and adsorbate-covered N-polar InN surfaces using in situ photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Eisenhardt, Anja; Himmerlich, Marcel; Krischok, Stefan

    2012-01-01

    The surface electronic properties and adsorption behaviour of as-grown and oxidized N-polar InN films are characterized by photoelectron spectroscopy (XPS, UPS). The epitaxial growth of the InN layers was performed by plasma-assisted molecular beam epitaxy on GaN/6H-SiC(000-1). After growth and in situ characterization the InN surfaces were exposed to molecular oxygen to evaluate the adsorption behaviour of O 2 on N-polar InN and to study its impact on the surface electronic properties of the III-nitride material. The results are compared with studies on In-polar InN on GaN/sapphire templates. The as-grown N-polar InN surface exhibits a pronounced surface state at a binding energy of ∝1.6 eV. The valence band minimum lies about 0.8-1.0 eV below the surface Fermi level. Additionally, the XPS core level binding energies for InN(000-1) are reduced compared to InN(0001) films, indicating different surface band bending for clean N-polar and In-polar InN, respectively. The interaction of molecular oxygen with the InN(000-1) surface leads to a downward band bending by 0.1 eV compared to the initial state. Additional adsorption of species from the residual gas of the UHV chamber increases the surface downward band bending. Furthermore two pronounced oxygen related states with an energy distance of ∝5 eV could be detected in the valence band region. The adsorbed oxygen results in an additional component in the N1s core level spectra, which is interpreted as formation of NO x bonds. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Structure, magnetic properties, polarized neutron diffraction, and theoretical study of a copper(II) cubane.

    Science.gov (United States)

    Aronica, Christophe; Chumakov, Yurii; Jeanneau, Erwann; Luneau, Dominique; Neugebauer, Petr; Barra, Anne-Laure; Gillon, Béatrice; Goujon, Antoine; Cousson, Alain; Tercero, Javier; Ruiz, Eliseo

    2008-01-01

    The paper reports the synthesis, X-ray and neutron diffraction crystal structures, magnetic properties, high field-high frequency EPR (HF-EPR), spin density and theoretical description of the tetranuclear CuII complex [Cu4L4] with cubane-like structure (LH2=1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J1 (+30.5 cm(-1)) and a weak antiferromagnetic interaction J2 (-5.5 cm(-1)), which correspond to short and long Cu-Cu distances, respectively, as evidence from the crystal structure [see formulate in text]. It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF-EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero-field splitting parameter D (-0.25+/-0.01 cm(-1)) plus a small rhombic term E (0.025+/-0.001 cm(-1), E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the CuII ion with a distortion of yz-type for one CuII ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations.

  9. High-power fiber laser with a polarizing diffraction grating milled on the facet of an optical fiber

    Czech Academy of Sciences Publication Activity Database

    Vaněk, Martin; Vaniš, Jan; Baravets, Yauhen; Todorov, Filip; Čtyroký, Jiří; Honzátko, Pavel

    2016-01-01

    Roč. 24, č. 26 (2016), s. 30225-30233 ISSN 1094-4087 R&D Projects: GA ČR GA15-07908S Institutional support: RVO:67985882 Keywords : Optical fibers * Polarization * Diffraction gratings Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.307, year: 2016

  10. High-power fiber laser with a polarizing diffraction grating milled on the facet of an optical fiber

    Czech Academy of Sciences Publication Activity Database

    Vaněk, Martin; Vaniš, Jan; Baravets, Yauhen; Todorov, Filip; Čtyroký, Jiří; Honzátko, Pavel

    2016-01-01

    Roč. 24, č. 26 (2016), s. 30225-30233 ISSN 1094-4087 R&D Projects: GA ČR GA15-07908S Institutional support: RVO:67985882 Keywords : Optical fiber s * Polarization * Diffraction gratings Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.307, year: 2016

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

    KAUST Repository

    Crumlin, Ethan J.; Mutoro, Eva; Hong, Wesley T.; Biegalski, Michael D.; Christen, Hans M.; Liu, Zhi; Bluhm, Hendrik; Shao-Horn, Yang

    2013-01-01

    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.

  12. 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.

  13. Development of Extended Ray-tracing method including diffraction, polarization and wave decay effects

    Science.gov (United States)

    Yanagihara, Kota; Kubo, Shin; Dodin, Ilya; Nakamura, Hiroaki; Tsujimura, Toru

    2017-10-01

    Geometrical Optics Ray-tracing is a reasonable numerical analytic approach for describing the Electron Cyclotron resonance Wave (ECW) in slowly varying spatially inhomogeneous plasma. It is well known that the result with this conventional method is adequate in most cases. However, in the case of Helical fusion plasma which has complicated magnetic structure, strong magnetic shear with a large scale length of density can cause a mode coupling of waves outside the last closed flux surface, and complicated absorption structure requires a strong focused wave for ECH. Since conventional Ray Equations to describe ECW do not have any terms to describe the diffraction, polarization and wave decay effects, we can not describe accurately a mode coupling of waves, strong focus waves, behavior of waves in inhomogeneous absorption region and so on. For fundamental solution of these problems, we consider the extension of the Ray-tracing method. Specific process is planned as follows. First, calculate the reference ray by conventional method, and define the local ray-base coordinate system along the reference ray. Then, calculate the evolution of the distributions of amplitude and phase on ray-base coordinate step by step. The progress of our extended method will be presented.

  14. Single crystal polarized neutron diffraction study of the magnetic structure of HoFeO3.

    Science.gov (United States)

    Chatterji, T; Stunault, A; Brown, P J

    2017-09-27

    Polarised neutron diffraction measurements have been made on HoFeO 3 single crystals magnetised in both the [0 0 1] and [1 0 0] directions (Pbnm setting). The polarisation dependencies of Bragg reflection intensities were measured both with a high field of [Formula: see text] T parallel to [0 0 1] at [Formula: see text] K and with the lower field [Formula: see text] T parallel to [1 0 0] at [Formula: see text] K. A Fourier projection of magnetization induced parallel to [0 0 1], made using the hk0 reflections measured in 9 T, indicates that almost all of it is due to alignment of Ho moments. Further analysis of the asymmetries of general reflections in these data showed that although, at 70 K, 9 T applied parallel to [0 0 1] hardly perturbs the antiferromagnetic order of the Fe sublattices, it induces significant antiferromagnetic order of the Ho sublattices in the [Formula: see text] plane, with the antiferromagnetic components of moment having the same order of magnitude as the induced ferromagnetic ones. Strong intensity asymmetries measured in the low temperature [Formula: see text] structure with a lower field, 0.5 T [Formula: see text] [1 0 0] allowed the variation of the ordered components of the Ho and Fe moments to be followed. Their absolute orientations, in the [Formula: see text] domain stabilised by the field were determined relative to the distorted perovskite structure. This relationship fixes the sign of the Dzyalshinski-Moriya (D-M) interaction which leads to the weak ferromagnetism. Our results indicate that the combination of strong y-axis anisotropy of the Ho moments and Ho-Fe exchange interactions breaks the centrosymmetry of the structure and could lead to ferroelectric polarization.

  15. Photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Shirley, D.A.

    1976-01-01

    Research activities in photoelectron spectroscopy at Lawrence Radiation Laboratory during 1976 are described. Topics covered include: the orientation of CO on Pt(III) and Ni(III) surfaces from angle-resolved photoemission; photoemission from CO on Pt(III) in the range 40 eV less than or equal to dirac constant ω less than or equal to 150 eV; photoemission studies of electron states at clean surfaces using synchrotron radiation; angle and energy dependent photoemission studies of plasmon loss structure in Al and In; d-orbital directed photoemission from copper; interpretation of angle-resolved x-ray photoemission from valence bands; atomic cross-section effects in soft x-ray photoemission from Ag, Au, and Pt valence bands; x-ray photoelectron spectroscopic studies of the electronic structure of transition metal difluorides; x-ray photoemission investigation of the density of states of B'-NiAl; the electronic structure of SrTiO 3 and some simple related oxides; fluorescence lifetime measurements of np 5 (n+1)S' states in krypton and xenon; Zeeman beats in the resonance fluorescence of the 3P 1 , states in krypton and xenon; lifetime measurements of rare-gas dimers; configuration interaction effects in the atomic photoelectron spectra of Ba, Sm, Eu, and Yb; glow discharge lamps as electron sources for electron impact excitation; electron impact excitation of electron correlation states in Ca, Sr, and Ba; photoelectron spectroscopy of atomic and molecular bismuth; relativistic effects in the uv photoelectron spectra of group VI diatomic molecules; and relative gas-phase acidities and basicities from a proton potential model

  16. Coherent Control of Photoelectron Wavepacket Angular Interferograms

    OpenAIRE

    Hockett, Paul; Wollenhaupt, Matthias; Baumert, Thomas

    2015-01-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the cohere...

  17. Observation of a reorientation of the holmium moments in HoAl2 with polarized neutron diffraction

    International Nuclear Information System (INIS)

    Barbara, B.; Boucherle, J.X.; Rossignol, M.F.; Schweizer, J.

    1976-01-01

    Magnetization measurements performed on a single crystal of HoAl 2 show that the easy axis of magnetization is [110] at low temperature and suggest near 20 0 K a rotation of the easy direction of magnetization. This rotation has been strikingly demonstrated by polarized neutron diffraction experiments including measurements of intensities with both spin states and of depolarization through the sample. This result allows the interpretation of the magnetic properties of HoAl 2 in terms of crystal field

  18. Photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Bosch, A.

    1982-01-01

    In this work examples of the various aspects of photoelectron spectroscopy are given. The investigation was started with the development of an angle-resolved spectrometer so that the first chapters deal with angle-resolved ultra-violet photoelectron spectroscopy. To indicate the possibilities and pitfalls of the technique, in chapter II the theory is briefly reviewed. In chapter III the instrument is described. The system is based on the cylindrical mirror deflection analyzer, which is modified and improved for angle-resolved photoelectron spectroscopy. In combination with a position sensitive detector, a spectrometer is developed with which simultaneously several angle-resolved spectra can be recorded. In chapter IV, the results are reported of angle-integrated UPS experiments on dilute alloys. Using the improved energy resolution of the instrument the author was able to study the impurity states more accurately and shows that the photoemission technique has become an important tool in the study of impurities and the interactions involved. XPS and Auger results obtained from dilute alloys are presented in chapter V. It is shown that these systems are especially suited for the study of correlation effects and can provide interesting problems related to the satellite structure and the interaction of the impurity with the host. In chapter VI, the valence bands of ternary alloys are studied with UPS and compared to recent band structure calculation. The core level shifts are analyzed in a simple, thermodynamic scheme. (Auth.)

  19. X-ray diffraction study of A- plane non-polar InN epilayer grown by MOCVD

    Science.gov (United States)

    Moret, Matthieu; Briot, Olivier; Gil, Bernard

    2015-03-01

    Strong polarisation-induced electric fields in C-plane oriented nitrides semiconductor layers reduce the performance of devices. Eliminating the polarization fields can be achieved by growing nitrides along non polar direction. We have grown non polar A-plane oriented InN on R-plane (1‾102) nitridated sapphire substrate by MOCVD. We have studied the structural anisotropy observed in these layers by analyzing High Resolution XRay Diffraction rocking curve (RC) experiments as a function of the in-plane beam orientation. A-plane InN epilayer have a unique epitaxial relationship on R-Plane sapphire and show a strong structural anisotropy. Full width at half maximum (FWHM) of the InN(11‾20) XRD RC values are contained between 44 and 81 Arcmin. FWHM is smaller when the diffraction occurs along the [0001] and the largest FWHM values, of the (11‾20) RC, are obtained when the diffraction occurs along the [1‾100] in-plane direction. Atomic Force Microscopy imaging revealed morphologies with well organized crystallites. The grains are structured along a unique crystallographic orientation of InN, leading to larger domains in this direction. This structural anisotropy can be, in first approximation, attributed to the difference in the domain sizes observed. XRD reciprocal space mappings (RSM) were performed in asymmetrical configuration on (13‾40) and (2‾202) diffraction plane. RSM are measured with a beam orientation corresponding to a maximal and a minimal width of the (11‾20) Rocking curves, respectively. A simple theoretical model is exposed to interpret the RSM. We concluded that the dominant contribution to the anisotropy is due to the scattering coherence length anisotropy present in our samples.

  20. Temperature-dependent surface structure, composition, and electronic properties of the clean SrTiO3(111) crystal face: Low-energy-electron diffraction, Auger-electron spectroscopy, electron energy loss, and ultraviolet-photoelectron spectroscopy studies

    International Nuclear Information System (INIS)

    Lo, W.J.; Somorjai, G.A.

    1978-01-01

    Low-energy-electron diffraction, Auger-electron spectroscopy, electron-energy-loss, and ultraviolet-photoelectron spectroscopies were used to study the structure, composition, and electron energy distribution of a clean single-crystal (111) face of strontium titanate (perovskite). The dependence of the surface chemical composition on the temperature has been observed along with corresponding changes in the surface electronic properties. High-temperature Ar-ion bombardment causes an irreversible change in the surface structure, stoichiometry, and electron energy distribution. In contrast to the TiO 2 surface, there are always significant concentrations of Ti 3+ in an annealed ordered SrTiO 3 (111) surface. This stable active Ti 3+ monolayer on top of a substrate with large surface dipole potential makes SrTiO 3 superior to TiO 2 when used as a photoanode in the photoelectrochemical cell

  1. Experimental determination of spin-dependent electron density by joint refinement of X-ray and polarized neutron diffraction data.

    Science.gov (United States)

    Deutsch, Maxime; Claiser, Nicolas; Pillet, Sébastien; Chumakov, Yurii; Becker, Pierre; Gillet, Jean Michel; Gillon, Béatrice; Lecomte, Claude; Souhassou, Mohamed

    2012-11-01

    New crystallographic tools were developed to access a more precise description of the spin-dependent electron density of magnetic crystals. The method combines experimental information coming from high-resolution X-ray diffraction (XRD) and polarized neutron diffraction (PND) in a unified model. A new algorithm that allows for a simultaneous refinement of the charge- and spin-density parameters against XRD and PND data is described. The resulting software MOLLYNX is based on the well known Hansen-Coppens multipolar model, and makes it possible to differentiate the electron spins. This algorithm is validated and demonstrated with a molecular crystal formed by a bimetallic chain, MnCu(pba)(H(2)O)(3)·2H(2)O, for which XRD and PND data are available. The joint refinement provides a more detailed description of the spin density than the refinement from PND data alone.

  2. Arbitrary Control of Polarization and Intensity Profiles of Diffraction-Attenuation-Resistant Beams along the Propagation Direction

    Science.gov (United States)

    Corato-Zanarella, Mateus; Dorrah, Ahmed H.; Zamboni-Rached, Michel; Mojahedi, Mo

    2018-02-01

    We report on the theory and experimental generation of a class of diffraction-attenuation-resistant beams with state of polarization (SOP) and intensity that can be controlled on demand along the propagation direction. This control is achieved by a suitable superposition of Bessel beams, whose parameters are systematically chosen based on closed-form analytic expressions provided by the frozen waves method. Using an amplitude-only spatial light modulator, we experimentally demonstrate three scenarios. In the first, the SOP of a horizontally polarized beam evolves to radial polarization and is then changed to vertical polarization, with the beam intensity held constant. In the second, we simultaneously control the SOP and the longitudinal intensity profile, which is chosen such that the beam's central ring can be switched off over predefined space regions, thus generating multiple foci with different SOPs and at different intensity levels along the propagation. Finally, the ability to control the SOP while overcoming attenuation inside lossy fluids is shown experimentally. We envision our proposed method to be of great interest for many applications, such as optical tweezers, atom guiding, material processing, microscopy, and optical communications.

  3. Simultaneous resonant x-ray diffraction measurement of polarization inversion and lattice strain in polycrystalline ferroelectrics

    DEFF Research Database (Denmark)

    Gorfman, S.; Simons, Hugh; Iamsasri, T.

    2016-01-01

    and strain in ferroelectrics is an ongoing challenge that so far has obscured its fundamental behaviour. By utilizing small intensity differences between Friedel pairs due to resonant scattering, we demonstrate a time-resolved X-ray diffraction technique for directly and simultaneously measuring both lattice...

  4. Characterization of an Yb:LuVO{sub 4} single crystal using X-ray topography, high-resolution X-ray diffraction, and X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Paszkowicz, W., E-mail: paszk@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02668 Warsaw (Poland); Romanowski, P.; Bak-Misiuk, J. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02668 Warsaw (Poland); Wierzchowski, W. [Institute of Electronic Materials Technology, Wolczynska 133, PL-01919 Warsaw (Poland); Wieteska, K. [Institute of Atomic Energy POLATOM, PL-05400 Otwock-Swierk (Poland); Graeff, W. [HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg (Germany); Iwanowski, R.J. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02668 Warsaw (Poland); Heinonen, M.H. [Laboratory of Materials Science, Department of Physics, University of Turku, Vesilinnantie 5, FI-20014, Turku (Finland); Ermakova, O. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02668 Warsaw (Poland); Dabkowska, H. [Department of Physics, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada)

    2011-10-15

    Knowledge on the defect and electronic structure allows for improved modeling of material properties. A short literature review has shown that the information on defect structure of rare earth orthovanadate single crystals is limited. In this paper, defect and electronic structure of a needle-shaped Yb:LuVO{sub 4} single crystal grown by the slow cooling method have been studied by means of X-ray diffraction topography employing white synchrotron beam, high-resolution diffraction (HRD) and photoelectron spectroscopy (XPS) techniques. Topographic investigations show that the crystal is composed of two blocks disoriented by about 1.5{sup o} and separated by a narrow deformed region. Some contrasts observed within the crystal volume may be attributed to glide bands and sector boundaries. The contrasts appearing in the vicinity of the surface may be interpreted as due to the presence of small inclusions. The HRD study indicates, in particular, that among point defects, the vacancy type defects dominate and that the density of other defects is small in comparison. The XPS measurements enabled, despite highly insulating properties of the studied crystal, an analysis of its bulk electronic structure, including the main core-levels (O 1s, V 2p, Lu 4f) as well as the valence band range.

  5. Polarized Neutron Diffraction to Probe Local Magnetic Anisotropy of a Low-Spin Fe(III) Complex.

    Science.gov (United States)

    Ridier, Karl; Mondal, Abhishake; Boilleau, Corentin; Cador, Olivier; Gillon, Béatrice; Chaboussant, Grégory; Le Guennic, Boris; Costuas, Karine; Lescouëzec, Rodrigue

    2016-03-14

    We have determined by polarized neutron diffraction (PND) the low-temperature molecular magnetic susceptibility tensor of the anisotropic low-spin complex PPh4 [Fe(III) (Tp)(CN)3]⋅H2O. We found the existence of a pronounced molecular easy magnetization axis, almost parallel to the C3 pseudo-axis of the molecule, which also corresponds to a trigonal elongation direction of the octahedral coordination sphere of the Fe(III) ion. The PND results are coherent with electron paramagnetic resonance (EPR) spectroscopy, magnetometry, and ab initio investigations. Through this particular example, we demonstrate the capabilities of PND to provide a unique, direct, and straightforward picture of the magnetic anisotropy and susceptibility tensors, offering a clear-cut way to establish magneto-structural correlations in paramagnetic molecular complexes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Coherent control of photoelectron wavepacket angular interferograms

    International Nuclear Information System (INIS)

    Hockett, P; Wollenhaupt, M; Baumert, T

    2015-01-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process, where the final (time-integrated) observable coherently samples all instantaneous states of the light–matter interaction. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the coherent control over the resultant photoelectron interferogram is thus explored in detail. Based on this understanding, the use of coherent control with polarization-shaped pulses as a methodology for a highly multiplexed coherent quantum metrology is also investigated, and defined in terms of the information content of the observable. (paper)

  7. Coherent control of photoelectron wavepacket angular interferograms

    Science.gov (United States)

    Hockett, P.; Wollenhaupt, M.; Baumert, T.

    2015-11-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process, where the final (time-integrated) observable coherently samples all instantaneous states of the light-matter interaction. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the coherent control over the resultant photoelectron interferogram is thus explored in detail. Based on this understanding, the use of coherent control with polarization-shaped pulses as a methodology for a highly multiplexed coherent quantum metrology is also investigated, and defined in terms of the information content of the observable.

  8. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments

    Directory of Open Access Journals (Sweden)

    Maxime Deutsch

    2014-05-01

    Full Text Available Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  9. Polarized Neutron Diffraction as a Tool for Mapping Molecular Magnetic Anisotropy: Local Susceptibility Tensors in Co(II) Complexes.

    Science.gov (United States)

    Ridier, Karl; Gillon, Béatrice; Gukasov, Arsen; Chaboussant, Grégory; Cousson, Alain; Luneau, Dominique; Borta, Ana; Jacquot, Jean-François; Checa, Ruben; Chiba, Yukako; Sakiyama, Hiroshi; Mikuriya, Masahiro

    2016-01-11

    Polarized neutron diffraction (PND) experiments were carried out at low temperature to characterize with high precision the local magnetic anisotropy in two paramagnetic high-spin cobalt(II) complexes, namely [Co(II) (dmf)6 ](BPh4 )2 (1) and [Co(II) 2 (sym-hmp)2 ](BPh4 )2 (2), in which dmf=N,N-dimethylformamide; sym-hmp=2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate, and BPh4 (-) =tetraphenylborate. This allowed a unique and direct determination of the local magnetic susceptibility tensor on each individual Co(II) site. In compound 1, this approach reveals the correlation between the single-ion easy magnetization direction and a trigonal elongation axis of the Co(II) coordination octahedron. In exchange-coupled dimer 2, the determination of the individual Co(II) magnetic susceptibility tensors provides a clear outlook of how the local magnetic properties on both Co(II) sites deviate from the single-ion behavior because of antiferromagnetic exchange coupling. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments.

    Science.gov (United States)

    Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

    2014-05-01

    Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  11. Effect of lattice distortion on uranium magnetic moments in U4Ru7Ge6 studied by polarized neutron diffraction

    Science.gov (United States)

    Vališka, Michal; Klicpera, Milan; Doležal, Petr; Fabelo, Oscar; Stunault, Anne; Diviš, Martin; Sechovský, Vladimír

    2018-03-01

    In a cubic ferromagnet, small spontaneous lattice distortions are expected below the Curie temperature, but the phenomenon is usually neglected. This study focuses on such an effect in the U4Ru7Ge6 compound. Based on DFT calculations, we propose a lattice distortion from the cubic I m -3 m space group to a lower, rhombohedral, symmetry described by the R -3 m space group. The strong spin-orbit coupling of the uranium ions plays an essential role in lowering the symmetry, giving rise to two different U sites (U1 and U2). Using polarized neutron diffraction in applied magnetic fields of 1 and 9 T in the ordered state (1.9 K ) and in the paramagnetic state (20 K ), we bring convincing experimental evidence of this splitting of the U sites, with different magnetic moments. The data have been analyzed both by maximum entropy calculations and by a direct fit in the dipolar approximation. In the ordered phase, the μL/μS ratio of the orbital and spin moments on the U2 site is remarkably lower than for the free U3 + or U4 + ion, which points to a strong hybridization of the U 5 f wave functions with the 4 d wave functions of the surrounding Ru. On the U1 site, the μL/μS ratio exhibits an unexpectedly low value: the orbital moment is almost quenched, like in metallic α -uranium. As a further evidence of the 5 f -4 d hybridization in the U4Ru7Ge6 system, we observe the absence of a magnetic moment on the Ru1 site, but a rather large induced moment on the Ru2 site, which is in closer coordination with both U positions. Very similar results are obtained at 20 K in the ferromagnetic regime induced by the magnetic field of 9 T . This shows that applying a strong magnetic field above the Curie temperature also leads to the splitting of the uranium sites, which further demonstrates the intimate coupling of the magnetic ordering and structural distortion. We propose that the difference between the magnetic moment on the U1 and U2 sites results from the strong spin

  12. Influence of Softening Temperature of Azobenzene Polymers and External Electric Field on Diffraction Efficiency of Polarization Holograms

    Directory of Open Access Journals (Sweden)

    Nicolay Davidenko

    2017-12-01

    Full Text Available Growth of the diffraction efficiency and recording velocity was found in the films of copolymers 4-((2- nitrophenyl diazeniylphenylmethacrylate with octylmethacrylate at room temperature holographic recording for copolymer with less softening temperature. Effect of strengthening of the diffraction efficiency was observed when charging surface of the films with recorded hologram in crown discharge.

  13. Photoelectron and x-ray holography by contrast: enhancing image quality and dimensionality

    Energy Technology Data Exchange (ETDEWEB)

    Fadley, C.S.; Zhao, L. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Department of Physics, University of California, Davis, CA (United States); Hove, M.A. van [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Department of Physics, University of California, Davis, CA (United States); Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Kaduwela, A.; Marchesini, S. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Omori, S. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Institute of Industrial Science, University of Tokyo, Tokyo (Japan); Sony Corporation Semiconductor Network Company, Asahi-cho, Atsugi, Kanagawa (Japan)

    2001-11-26

    Three forms of electron or x-ray holography 'by contrast' are discussed: they all exploit small changes in diffraction conditions to improve image quality and/or extract additional information. Spin-polarized photoelectron holography subtracts spin-down from spin-up holograms so as to image the relative orientations of atomic magnetic moments around an emitter atom. Differential photoelectron holography subtracts holograms taken at slightly different energies so as to overcome the forward-scattering problem that normally degrades the three-dimensional imaging of atoms, particularly for emitter atoms that are part of a bulk substrate environment. Resonant x-ray fluorescence holography also subtracts holograms at slightly different energies, these being chosen above and below an absorption edge of a constituent atom, thus allowing the selective imaging of that type of atom, or what has been referred to as imaging 'in true colour'. (author)

  14. When combined X-ray and polarized neutron diffraction data challenge high-level calculations: spin-resolved electron density of an organic radical.

    Science.gov (United States)

    Voufack, Ariste Bolivard; Claiser, Nicolas; Lecomte, Claude; Pillet, Sébastien; Pontillon, Yves; Gillon, Béatrice; Yan, Zeyin; Gillet, Jean Michel; Marazzi, Marco; Genoni, Alessandro; Souhassou, Mohamed

    2017-08-01

    Joint refinement of X-ray and polarized neutron diffraction data has been carried out in order to determine charge and spin density distributions simultaneously in the nitronyl nitroxide (NN) free radical Nit(SMe)Ph. For comparison purposes, density functional theory (DFT) and complete active-space self-consistent field (CASSCF) theoretical calculations were also performed. Experimentally derived charge and spin densities show significant differences between the two NO groups of the NN function that are not observed from DFT theoretical calculations. On the contrary, CASSCF calculations exhibit the same fine details as observed in spin-resolved joint refinement and a clear asymmetry between the two NO groups.

  15. Polarized single crystal neutron diffraction study of the zero-magnetization ferromagnet Sm1 -xGdxAl2 (x =0.024 )

    Science.gov (United States)

    Chatterji, T.; Stunault, A.; Brown, P. J.

    2018-02-01

    We have determined the temperature evolution of the spin and orbital moments in the zero-magnetization ferromagnet Sm1 -xGdxAl2 (x = 0.024) by combining polarized and unpolarized single crystal neutron diffraction data. The sensitivity of the polarized neutron technique has allowed the moment values to be determined with a precision of ≈0.1 μB . Our results clearly demonstrate that, when magnetized by a field of 8 T, the spin and orbital moments in Sm1 -xGdxAl2 are oppositely directed, so that the net magnetization is very small. Below 60 K the contributions from spin and orbital motions are both about 2 μB , with that due to orbital motion being slightly larger than that due to spin. Between 60 and 65 K the contributions of each to the magnetization fall rapidly and change sign at Tcomp ≈67 K , above which the aligned moments recover but with the orbital magnetization still slightly higher than the spin one. These results imply that above Tcomp the small resultant magnetization of the Sm3 + ion is oppositely directed to the magnetizing field. It is suggested that this anomaly is due to polarization of conduction electron spin associated with the doping Gd3 + ions.

  16. Study of the ultrafast polarization dynamics in lithium borohydride by means of femtosecond X-ray diffraction

    International Nuclear Information System (INIS)

    Stingl, Johannes

    2013-01-01

    In this thesis the ultrafast electronic polarisation in the crystalline material lithium borohydride (LiBH 4 ) is examined. The material is excited by a femtosecond long optical pulse and scanned by a likewise short X-ray pulse. Using X-ray scattering the optically induced spatial rearrangement of electronic charge can be directly mapped with atomic spatial resolution. Copper K-alpha X-rays for the experiment are produced in a laboratory table-top laserplasma source with 1 kHz repetition rate. This radiation is then focused on a powdered sample. Debye-Scherrer rings produced from powder diffraction are collected on a large area detector and processed to yield intensity profiles. Using pump-probe technique the change in diffracted intensity, triggered by excitation with a femtosecond optical pulse is examined. The temporal resolution is given by the delay between pump and probe pulse. This way insight is gained into the dynamic electronic evolution of the system. Intensity changes can be correlated to changes in charge density in the relevant material to elucidate structural dynamics on the femtosecond time scale. Lithium borohydride was chosen since it displays necessary characteristics for the exploration of ultrafast electronic polarisation. Up to date there has been no spatially resolved research in the femtosecond regime elucidating this electronic phenomenon. This work presents the ultrafast resonse in Lithiumborhydrid (LiBH 4 ) to strong electronic fields with optical frequencies, which leads to charge relocation accompanied by electronic polarisation.

  17. Electronic interaction in an outer-sphere mixed-valence double salt: a polarized neutron diffraction study of K(3)(MnO(4))(2).

    Science.gov (United States)

    Cannon, Roderick D; Jayasooriya, Upali A; Tilford, Claire; Anson, Christopher E; Sowrey, Frank E; Rosseinsky, David R; Stride, John A; Tasset, Francis; Ressouche, Eric; White, Ross P; Ballou, Rafik

    2004-11-01

    The mixed-valence double salt K(3)(MnO(4))(2) crystallizes in space group P2(1)/m with Z = 2. The manganese centers Mn1 and Mn2 constitute discrete "permanganate", [Mn(VII)O(4)](-), and "manganate", [Mn(VI)O(4)](2-), ions, respectively. There is a spin-ordering transition to an antiferromagnetic state at ca. T = 5 K. The spin-density distribution in the paramagnetic phase at T = 10 K has been determined by polarized neutron diffraction, confirming that unpaired spin is largely confined to the nominal manganate ion Mn2. Through use of both Fourier refinement and maximum entropy methods, the spin on Mn1 is estimated as 1.75 +/- 1% of one unpaired electron with an upper limit of 2.5%.

  18. Ferromagnetic interaction in an asymmetric end-to-end azido double-bridged copper(II) dinuclear complex: a combined structure, magnetic, polarized neutron diffraction and theoretical study.

    Science.gov (United States)

    Aronica, Christophe; Jeanneau, Erwann; El Moll, Hani; Luneau, Dominique; Gillon, Béatrice; Goujon, Antoine; Cousson, Alain; Carvajal, Maria Angels; Robert, Vincent

    2007-01-01

    A new end-to-end azido double-bridged copper(II) complex [Cu(2)L(2)(N(3))2] (1) was synthesized and characterized (L=1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato). Despite the rather long Cu-Cu distance (5.105(1) A), the magnetic interaction is ferromagnetic with J= +16 cm(-1) (H=-JS(1)S(2)), a value that has been confirmed by DFT and high-level correlated ab initio calculations. The spin distribution was studied by using the results from polarized neutron diffraction. This is the first such study on an end-to-end system. The experimental spin density was found to be localized mainly on the copper(II) ions, with a small degree of delocalization on the ligand (L) and terminal azido nitrogens. There was zero delocalization on the central nitrogen, in agreement with DFT calculations. Such a picture corresponds to an important contribution of the d(x2-y2) orbital and a small population of the d(z2) orbital, in agreement with our calculations. Based on a correlated wavefunction analysis, the ferromagnetic behavior results from a dominant double spin polarization contribution and vanishingly small ionic forms.

  19. Photoelectronic properties of semiconductors

    CERN Document Server

    Bube, Richard H

    1992-01-01

    The interaction between light and electrons in semiconductors forms the basis for many interesting and practically significant properties. This book examines the fundamental physics underlying this rich complexity of photoelectronic properties of semiconductors, and will familiarise the reader with the relatively simple models that are useful in describing these fundamentals. The basic physics is also illustrated with typical recent examples of experimental data and observations. Following introductory material on the basic concepts, the book moves on to consider a wide range of phenomena, including photoconductivity, recombination effects, photoelectronic methods of defect analysis, photoeffects at grain boundaries, amorphous semiconductors, photovoltaic effects and photoeffects in quantum wells and superlattices. The author is Professor of Materials Science and Electrical Engineering at Stanford University, and has taught this material for many years. He is an experienced author, his earlier books having fo...

  20. Spin analysis of photoelectrons by using synchrotron radiation

    International Nuclear Information System (INIS)

    Yagishita, Akira

    1983-03-01

    This report is the proceedings of a workshop on ''Spin analysis of photoelectrons by using synchrotron radiation'' held at National Laboratory for High Energy Physics on October 21, 1982. The purpose of this workshop was to examine the feasibility of the experiment on the spin analysis of photoelectrons at the photon factory which has started the operation in 1982. The workshop covered the following subjects on the spin analysis of photoelectrons and on the detectors for spin polarization; the experiment and the theory on the spin analysis of photoelectrons emitted from gas and solid, the detectors for measuring the spin polarization of electron beam, the test experiment on a Mott detector, and further problems. The proceedings contain five papers related to the above subjects. (Asami, T.)

  1. Photoelectronic characterization of heterointerfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Brumbach, Michael Todd

    2012-02-01

    In many devices such as solar cells, light emitting diodes, transistors, etc., the performance relies on the electronic structure at interfaces between materials within the device. The objective of this work was to perform robust characterization of hybrid (organic/inorganic) interfaces by tailoring the interfacial region for photoelectron spectroscopy. Self-assembled monolayers (SAM) were utilized to induce dipoles of various magnitudes at the interface. Additionally, SAMs of molecules with varying dipolar characteristics were mixed into spatially organized structures to systematically vary the apparent work function. Polymer thin films were characterized by depositing films of varying thicknesses on numerous substrates with and without interfacial modifications. Hard X-ray photoelectron spectroscopy (HAXPES) was performed to evaluate a buried interface between indium tin oxide (ITO), treated under various conditions, and poly(3-hexylthiophene) (P3HT). Conducting polymer films were found to be sufficiently conducting such that no significant charge redistribution in the polymer films was observed. Consequently, a further departure from uniform substrates was taken whereby electrically disconnected regions of the substrate presented ideally insulating interfacial contacts. In order to accomplish this novel strategy, interdigitated electrodes were used as the substrate. Conducting fingers of one half of the electrodes were electrically grounded while the other set of electrodes were electronically floating. This allowed for the evaluation of substrate charging on photoelectron spectra (SCOPES) in the presence of overlying semiconducting thin films. Such an experiment has never before been reported. This concept was developed out of the previous experiments on interfacial modification and thin film depositions and presents new opportunities for understanding chemical and electronic changes in a multitude of materials and interfaces.

  2. Electron spin polarization effects in low-energy electron diffraction, ion neutralization, and metastable-atom deexcitation at solid surfaces. Progress report No. 3, January 1-December 31, 1983

    International Nuclear Information System (INIS)

    Walters, G.K.; Dunning, F.B.

    1983-01-01

    The importance of electron spin polarization (ESP) effects in the various spectroscopies used to study solid surfaces has become increasingly apparent in recent years. Recent low energy electron diffraction (LEED) investigations in this laboratory and elsewhere have shown that a great deal of new information contributing to the understanding of the geometrical arrangements of atoms at a surface can be obtained if the polarization of the various LEED beams is measured, or if the incident electron beam is polarized. Polarized LEED studies have shown large polarization features that are very sensitive to the presence of adsorbed layers, surface reconstruction, etc. In addition, theory suggests that polarization measurements can provide a more sensitive test of many of the parameters used in a surface model than can conventional LEED intensity measurements alone. Polarized LEED has also been applied to the study of surface magnetism. In the present contract year, polarized LEED has been used, together with Auger analysis and LEED intensity measurements, as a diagnostic to characterize Ni(001) surfaces produced by laser annealing

  3. High resolution photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Arko, A.J.

    1988-01-01

    Photoelectron Spectroscopy (PES) covers a very broad range of measurements, disciplines, and interests. As the next generation light source, the FEL will result in improvements over the undulator that are larger than the undulater improvements over bending magnets. The combination of high flux and high inherent resolution will result in several orders of magnitude gain in signal to noise over measurements using synchrotron-based undulators. The latter still require monochromators. Their resolution is invariably strongly energy-dependent so that in the regions of interest for many experiments (h upsilon > 100 eV) they will not have a resolving power much over 1000. In order to study some of the interesting phenomena in actinides (heavy fermions e.g.) one would need resolving powers of 10 4 to 10 5 . These values are only reachable with the FEL

  4. X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Attekum, P.M.T.M. van.

    1979-01-01

    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.)

  5. Photoelectron emission from thin overlayers

    International Nuclear Information System (INIS)

    Jablonski, A.

    2012-01-01

    Highlights: ► Weak influence of the support on photoemission from an overlayer. ► Accurate description of photoelectron intensity from overlayer by analytical theory. ► Method for overlayer thickness measurements based on analytical formalism. ► Influence of photoelectron elastic scattering on calculated thickness. -- Abstract: Photoelectron signal intensities calculated for a thin overlayer from theoretical models taking elastic photoelectron collisions into account are shown to be very weakly dependent on the substrate material. This result has been obtained for photoelectrons analyzed in XPS spectrometers equipped with typical X-ray sources, i.e. sources of Mg Kα and Al Kα radiation. Low sensitivity to the substrate material is due to the fact that trajectories of photoelectrons emitted in the overlayer and entering the substrate have a low probability to reach the analyzer without energy loss. On the other hand, the signal intensity of photoelectrons emitted in the overlayer is found to be distinctly affected by elastic photoelectron scattering. Consequently, a theoretical model that can accurately describe the photoelectron intensity from an overlayer deposited on any material (e.g. on a substrate of the same material as the overlayer) can be a useful basis for a universal and convenient method for determination of the overlayer thickness. It is shown that the formalism derived from the kinetic Boltzmann equation within the so-called transport approximation satisfies these requirements. This formalism is postulated for use in overlayer-thickness measurements to avoid time-consuming Monte Carlo simulations of photoelectron transport, and also to circumvent problems with determining the effective attenuation lengths for overlayer/substrate systems.

  6. Observation of atomic arrangement by using photoelectron holography and atomic stereo-photograph

    International Nuclear Information System (INIS)

    Matsushita, Tomohiro; Guo, Fang Zhun; Agui, Akane; Matsui, Fumihiko; Daimon, Hiroshi

    2006-01-01

    Both a photoelectron holography and atomic stereo-photograph are the atomic structure analysis methods on the basis of photoelectron diffraction. They have six special features such as 1) direct determination of atomic structure, 2) measurement of three dimensional atomic arrangements surrounding of specific element in the sample, 3) determination of position of atom in spite of electron cloud, 4) unnecessary of perfect periodic structure, 5) good sensitivity of structure in the neighborhood of surface and 6) information of electron structure. Photoelectron diffraction, the principle and measurement system of photoelectron holography and atomic stereo-photograph is explained. As application examples of atomic stereo-photograph, the single crystal of cupper and graphite are indicated. For examples of photoelectron holography, Si(001)2p and Ge(001)3s are explained. (S.Y.)

  7. Photoelectron spectroscopy and spectro-microscopy of Pb(Zr,Ti)O{sub 3} (1 1 1) thin layers: Imaging ferroelectric domains with binding energy contrast

    Energy Technology Data Exchange (ETDEWEB)

    Huşanu, Marius A.; Popescu, Dana G.; Tache, Cristian A. [National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele-Ilfov (Romania); Apostol, Nicoleta G. [National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele-Ilfov (Romania); Elettra Sincrotrone Trieste, S.S. 14 – km 163,5, Area Science Park, 34169 Basovizza-Trieste (Italy); Barinov, Alexei; Lizzit, Silvano; Lacovig, Paolo [Elettra Sincrotrone Trieste, S.S. 14 – km 163,5, Area Science Park, 34169 Basovizza-Trieste (Italy); Teodorescu, Cristian M., E-mail: teodorescu@infim.ro [National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele-Ilfov (Romania)

    2015-10-15

    Graphical abstract: - Highlights: • Achievement of well ordered PZT(1 1 1) surfaces with reasonable low energy electron diffraction patterns and good stoichiometry. • Ability of photoelectron spectromicroscopy to visualize ferroelectric domains with contrast of binding energy. • Model taking into account the influence of photogenerated carriers on the depolarization field and its torque on the polarization vector. • Evidence of domain wall migration induced by photogenerated carriers. • Segregation of metal Pb only on areas with out-of-plane component of the polarization pointing outwards. - Abstract: The ability of photoelectron spectro-microscopy with sub-micrometer lateral resolution to identify ferroelectric domains by analysis of surface band bendings is demonstrated on lead zirco-titanate PZT(1 1 1) thin films grown by pulsed laser deposition. Conventional synchrotron radiation X-ray photoelectron spectroscopy allowed one to derive the surface composition of the sample and evidenced shifts toward higher binding energy when the sample is subject to intense soft X-ray beam. A basic model is developed which supposes that photogenerated carriers reduce the depolarization field, yielding a lower torque applied to the ferroelectric polarization. As a consequence, the out-of-plane component of the polarization increases. Domain migration during irradiation with soft X-ray is inferred from the relative amplitude of the components with different binding energy. When the flux density of soft X-ray is on the order of 10{sup 11} photons/(s μm{sup 2}), metal Pb clusters are formed at the surface on areas with the out-of-plane component of the polarization pointing outwards only.

  8. Structural and electronic properties of polar MnO ultrathin film grown on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Asish K., E-mail: asish.kundu@saha.ac.in; Menon, Krishnakumar S. R. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 70064 (India)

    2016-05-23

    Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

  9. Electron spin polarization effects in low energy electron diffraction, ion neutralization and metastable atom deexcitation at solid surfaces. Progress report No. 4, 1 January-31 December 1984

    International Nuclear Information System (INIS)

    1984-01-01

    In the present contract year, a GaAs polarized electron source has been used to undertake a polarized LEED study of order-disorder transformations at Cu 3 Au (100) and (111) surfaces. A polarized LEED study of Cu (100) has also been initiated. A polarized MDS study of Ni(110) surface magnetism has been completed. Spin dependences in the Auger electron yield were observed that provide a measure of the surface magnetism and were used to probe the dependence of surface magnetism on temperature and adsorbate coverage. A similar study using a ferromagnetic glass is now underway. A Mott polarization analyzer, constructed to measure the ESP of the ejected electrons, is also being installed on the apparatus. Such measurements provide direct information concerning the dynamics of secondary electron ejection and the details of adsorbate-substrate bonding

  10. Gluon polarization measurements and the possible role of diffractive process in the transverse single spin asymmetry measurements in RHIC-PHENIX

    Directory of Open Access Journals (Sweden)

    Nakagawa Itaru

    2017-01-01

    Full Text Available Two selected topics from the latest RHIC spin results are discussed here. For the transversely polarized spin program, an unexpectedly large single spin asymmetry in the very forward neutron production observed in polarized proton + nucleus collisions at √s = 200 GeV is discussed in this document. For the longitudinal program, the latest highlights from the measurements on the gluon spin components of the proton spin is discussed. After a decade of continuous efforts to hunt for the gluon polarization, the RHIC collaboration is about to catch the tail of the experimental evidence that gluon carries substantially large portion of the proton spin.

  11. Polarization experiments

    International Nuclear Information System (INIS)

    Halzen, F.

    1977-02-01

    In a theoretical review of polarization experiments two important points are emphasized: (a) their versatility and their relevance to a large variety of aspects of hadron physics (tests of basic symmetries; a probe of strong interaction dynamics; a tool for hadron spectroscopy); (b) the wealth of experimental data on polarization parameters in pp and np scattering in the Regge language and in the diffraction language. (author)

  12. 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...

  13. Angle-resolved photoelectron spectroscopy of cyclopropane

    Science.gov (United States)

    Keller, P. R.; Taylor, J. W.; Carlson, Thomas A.; Whitley, T. A.; Grimm, F. A.

    1985-10-01

    The angular distribution parameter, β, determined for the valence orbitals (IP < 18 eV) of cyclopropane in the 10-30 eV photon energy range using dispersed polarized synchrotron radiation. The energy dependence of β for photoelectron energies between, 2 and 10 eV above threshold was found to be similar to those found previously for other σ orbitals. The effects of Jahn-Teller splitting on β for the 3e' orbital were found to be small but definitely present. The overall shape and magnitude of the β( hv) curve are, however, sufficiently for the different Jahn-Teller components that, for purposes of orbital assignments using β( hv) curves the shape and magnitude of the curves can be considered associated only with the initial state. Resonance photoionization features at a photon ener of ≈ 18 eV were observed in the 3e' and 3a' 1 orbitals and tentatively assigned to autoionization.

  14. Imaging photoelectrons formed in strong laser fields

    International Nuclear Information System (INIS)

    Helm, H.; Dyer, M.J.; Saeed, M.; Huestis, D.L.

    1993-01-01

    An instrument capable of characterizing the angular correlation and energy distribution of products from photoionization of single atoms or molecules will be described. An external electric field is used to project individual charged particles generated in multiphoton ionization from the focal volume onto two-dimensional detectors. Digital images are recorded for each laser shot and summed. These images provide a direct view of the angular nodal plants of the photoelectrons and they can be analyzed to represent the spatial and energy distributions in the form of a polar plot, f(E,Θ). We discuss the application of this instrument to short pulse photoionization of rare gases and molecular hydrogen at visible and UV wavelengths at intensities ranging from 10 13 to 10 15 W/cm 2

  15. Diffractive interactions

    International Nuclear Information System (INIS)

    Del Duca, V.; Marage, P.

    1996-08-01

    The general framework of diffractive deep inelastic scattering is introduced and reports given in the session on diffractive interactions at the international workshop on deep-inelastic scattering and related phenomena, Rome, April 1996, are presented. (orig.)

  16. Photoelectron photoion molecular beam spectroscopy

    International Nuclear Information System (INIS)

    Trevor, D.J.

    1980-12-01

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

  17. Photoelectron antibunching and absorber theory

    International Nuclear Information System (INIS)

    Pegg, D.T.

    1980-01-01

    The recently detected photoelectron antibunching effect is considered to be evidence for the quantised electromagnetic field, i.e. for the existence of photons. Direct-action quantum absorber theory, on the other hand, has been developed on the basis that the quantised field is illusory, with quantisation being required only for atoms. In this paper it is shown that photoelectron antibunching is readily explicable in terms of absorber theory and in fact is directly attributable to the quantum nature of the emitting and detecting atoms alone. The physical nature of the reduction of the wavepacket associated with the detection process is briefly discussed in terms of absorber theory. (author)

  18. Diffraction theory

    NARCIS (Netherlands)

    Bouwkamp, C.J.

    1954-01-01

    A critical review is presented of recent progress in classical diffraction theory. Both scalar and electromagnetic problems are discussed. The report may serve as an introduction to general diffraction theory although the main emphasis is on diffraction by plane obstacles. Various modifications of

  19. Diffraction model analysis of vector polarized 6Li elastic scattering on 12C, 16O, 28Si, and 58Ni nuclei

    International Nuclear Information System (INIS)

    Rabie, A.; El-Gazzar, M.A.; Abul-Magd, A.Y.

    1980-11-01

    Using an assumption concerning the spin-orbit potential, it was possible to reduce the five amplitudes of scattering of spin-1 projectiles to two amplitudes. The summations over the partial waves were evaluated by the Regge pole technique. The resulting simple expressions were used to analyze the data of the Heidelberg group for polarized 6 Li ions scattered on 12 C, 16 O, 28 Si and 58 Ni to give a reasonable fitting both for the differential cross-section and vector polarization. (author)

  20. Polarized neutron spectrometer

    International Nuclear Information System (INIS)

    Abov, Yu.G.; Novitskij, V.V.; Alfimenkov, V.P.; Galinskij, E.M.; Mareev, Yu.D.; Pikel'ner, L.B.; Chernikov, A.N.; Lason', L.; Tsulaya, V.M.; Tsulaya, M.I.

    2000-01-01

    The polarized neutron spectrometer, intended for studying the interaction of polarized neutrons with nuclei and condensed media in the area of energies from thermal up to several electron-volt, is developed at the IBR-2 reactor (JINR, Dubna). Diffraction on the Co(92%)-Fe(8%) magnetized monocrystals is used for the neutron polarization and polarization analysis. The neutron polarization within the whole energy range equals ∼ 95% [ru

  1. Photoelectron spectroscopy an introduction to ultraviolet photoelectron spectroscopy in the gas phase

    CERN Document Server

    Eland, J H D

    2013-01-01

    Photoelectron Spectroscopy: An Introduction to Ultraviolet Photoelectronspectroscopy in the Gas Phase, Second Edition Photoelectron Spectroscopy: An Introduction to Ultraviolet PhotoelectronSpectroscopy in the Gas Phase, Second Edition aims to give practical approach on the subject of photoelectron spectroscopy, as well as provide knowledge on the interpretation of the photoelectron spectrum. The book covers topics such as the principles and literature of photoelectron microscopy; the main features and analysis of photoelectron spectra; ionization techniques; and energies from the photoelectron spectra. Also covered in the book are topics suc as photoelectron band structure and the applications of photoelectron spectroscopy in chemistry. The text is recommended for students and practitioners of chemistry who would like to be familiarized with the concepts of photoelectron spectroscopy and its importance in the field.

  2. Theory of photoelectron counting statistics

    International Nuclear Information System (INIS)

    Blake, J.

    1980-01-01

    The purpose of the present essay is to provide a detailed analysis of those theoretical aspects of photoelectron counting which are capable of experimental verification. Most of our interest is in the physical phenomena themselves, while part is in the mathematical techniques. Many of the mathematical methods used in the analysis of the photoelectron counting problem are generally unfamiliar to physicists interested in the subject. For this reason we have developed the essay in such a fashion that, although primary interest is focused on the physical phenomena, we have also taken pains to carry out enough of the analysis so that the reader can follow the main details. We have chosen to present a consistently quantum mechanical version of the subject, in that we follow the Glauber theory throughout. (orig./WL)

  3. Liquid microjet for photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Winter, Bernd

    2009-01-01

    Photoelectron spectroscopy from highly volatile liquids, especially from water and aqueous solutions, has recently become possible due to the development of the vacuum liquid microjet in combination of high-brilliance synchrotron radiation. The present status of this rapidly growing field is reported here, with an emphasize on the method's sensitivity for detecting local electronic structure, and for monitoring ultrafast dynamical processes in aqueous solution exploiting core-level resonant excitation.

  4. Liquid microjet for photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Winter, Bernd [Helmholtz-Zentrum Berlin fuer Materialien und Energie, and BESSY, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany)], E-mail: bernd.winter@bessy.de

    2009-03-21

    Photoelectron spectroscopy from highly volatile liquids, especially from water and aqueous solutions, has recently become possible due to the development of the vacuum liquid microjet in combination of high-brilliance synchrotron radiation. The present status of this rapidly growing field is reported here, with an emphasize on the method's sensitivity for detecting local electronic structure, and for monitoring ultrafast dynamical processes in aqueous solution exploiting core-level resonant excitation.

  5. Holographic atom imaging from experimental photoelectron angular distribution patterns

    International Nuclear Information System (INIS)

    Terminello, L.J.; Lapiano-Smith, D.A.; Barton, J.J.; Shirley, D.A.

    1993-11-01

    One of the most challenging areas of materials research is the imaging of technologically relevant materials with microscopic and atomic-scale resolution. As part of the development of these methods, near-surface atoms in single crystals were imaged using core-level photoelectron holograms. The angle-dependent electron diffraction patterns that constitute an electron hologram were two-dimensionally transformed to create a three dimensional, real-space image of the neighboring scattering atoms. They have made use of a multiple-wavenumber, phased-summing method to improve the atom imaging capabilities of experimental photoelectron holography using the Cu(001) and Pt(111) prototype systems. These studies are performed to evaluate the potential of holographic atom imaging methods as structural probes of unknown materials

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

    International Nuclear Information System (INIS)

    Davis, R.F.

    1981-11-01

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

  7. Photoelectron spectroscopy of molecular beams

    International Nuclear Information System (INIS)

    Berkowitz, J.

    1974-01-01

    The history of physical science is replete with examples of phenomena initially discovered and investigated by physicists, which have subsequently become tools of the chemist. It is demonstrated in this paper that the field of photoelectron spectroscopy may develop in a reverse fashion. After a brief introduction to the subject, the properties characterized as physical ones, are discussed. These are intensities and angular distributions, from which one can infer transition probabilities and phase shifts. Three separate experiments are described which involve accurate intensity measurements and it is shown how an interpretation of the results by appropriate theory has given new insight into the photoionization process. (B.R.H.)

  8. Practical scaling law for photoelectron angular distributions

    International Nuclear Information System (INIS)

    Guo Dongsheng; Zhang Jingtao; Xu Zhizhan; Li Xiaofeng; Fu Panming; Freeman, R.R.

    2003-01-01

    A practical scaling law that predicts photoelectron angular distributions (PADs) is derived using angular distribution formulas which explicitly contain spontaneous emission. The scaling law is used to analyze recent PAD measurements in above-threshold ionization, and to predict results of future experiments. Our theoretical and numerical studies show that, in the non-relativistic regime and long-wavelength approximation, the shapes of PADs are determined by only three dimensionless numbers: (1) u p ≡U p /(ℎ/2π)ω, the ponderomotive number (ponderomotive energy in units of laser photon energy); (2) ε b ≡E b /(ℎ/2π)ω, the binding number (atomic binding energy in units of the laser photon energy); (3) j, the absorbed-photon number. The scaling law is shown to be useful in predictions of results from strong-field Kapitza-Dirac effect measurements; specifically, the application of this scaling law to recently reported Kapitza-Dirac diffraction is discussed. Possible experimental tests to verify the scaling law are suggested

  9. Angle-resolved photoelectron spectroscopy of formaldehyde and methanol

    Science.gov (United States)

    Keller, P. R.; Taylor, J. W.; Grimm, F. A.; Carlson, Thomas A.

    1984-10-01

    Angle-resolved photoelectron spectroscopy was employed to obtain the angular distribution parameter, β, for the valence orbitals (IP < 21.1 eV) of formaldehyde and methanol over the 10-30 eV photon energy range using dispersed polarized synchrotron radiation as the excitation source. It was found that the energy dependence of β in the photoelectron energy range between 2 and 10 eV can be related to the molecular-orbital type from which ionization occurs. This generalized energy behavior is discussed with regard to earlier energy-dependence studies on molecules of different orbital character. Evidence is presented for the presence of resonance photoionization phenomena in formaldehyde in agreement with theoretical cross-section calculations.

  10. Photoelectron interference fringes by super intense x-ray laser pulses

    International Nuclear Information System (INIS)

    Toyota, Koudai; Morishita, Toru; Watanabe, Shinichi; Tolstikhin, Oleg I

    2009-01-01

    The photoelectron spectra of H - produced by circularly polarized strong high-frequency laser pulses are theoretically studied. An oscillating substructure in the above-threshold ionization (ATI) peaks is observed, which extends the validity of the earlier findings in the 1D calculations [K. Toyota et al., Phys. Rev. A 76, 043418 (2007)] and 3D calculations for linear polarization [O. I. Tolstikhin, Phys. Rev. A 77, 032712 (2008)]. Its origin is due to an interference between a pair of photoelectron wave packets created in the rising and falling part of the pulse, which appears clearly in the stabilization regime.

  11. Polarized Electrons for Linear Colliders

    International Nuclear Information System (INIS)

    Clendenin, J.

    2004-01-01

    Future electron-positron linear colliders require a highly polarized electron beam with a pulse structure that depends primarily on whether the acceleration utilizes warm or superconducting rf structures. The International Linear Collider (ILC) will use cold structures for the main linac. It is shown that a dc-biased polarized photoelectron source such as successfully used for the SLC can meet the charge requirements for the ILC micropulse with a polarization approaching 90%

  12. Diffraction dissociation

    International Nuclear Information System (INIS)

    Abarbanel, H.

    1972-01-01

    An attempt is made to analyse the present theoretical situation in the field of diffraction scattering. Two not yet fully answered questions related with a typical diffraction process AB→CD, namely: what is the structure of the transition matrix elements, and what is the structure of the exchange mechanism responsible for the scattering, are formulated and various proposals for answers are reviewed. Interesting general statement that the products (-1)sup(J)P, where J and P are respectively spin and parity, is conserved at each vertex has been discussed. The exchange mechanism in diffractive scattering has been considered using the language of the complex J-plane as the most appropriate. The known facts about the exchange mechanism are recalled and several routs to way out are proposed. The idea to consider the moving pole and associated branch points as like a particle and the associated two and many particle unitarity cuts is described in more details. (S.B.)

  13. Diffraction attraction

    International Nuclear Information System (INIS)

    Anon.

    1986-01-01

    Elastic scattering – when colliding particles 'bounce' off each other like billiard balls – has always had a special interest for high energy physicists. While its simplicity makes for deep analogies with classical ideas like diffraction, its jbtle details also test our understanding of the intricate inner mechanisms which drive particle interactions. With a new stock of elastic scattering data now available thanks to experiments at the CERN proton-antiproton Collider, and with studies at higher energies imminent or planned, some seventy physicists gathered in the magnificent chateau at Blois, France, for a 'Workshop on Elastic and Diffractive Scattering at the Collider and Beyond'

  14. Diffractive scattering

    CERN Document Server

    De Wolf, E.A.

    2002-01-01

    We discuss basic concepts and properties of diffractive phenomena in soft hadron collisions and in deep-inelastic scattering at low Bjorken-x. The paper is not a review of the rapidly developing field but presents an attempt to show in simple terms the close inter-relationship between the dynamics of high-energy hadronic and deep-inelastic diffraction. Using the saturation model of Golec-Biernat and Wusthoff as an example, a simple explanation of geometrical scaling is presented. The relation between the QCD anomalous multiplicity dimension and the Pomeron intercept is discussed.

  15. Diffractive Scattering

    International Nuclear Information System (INIS)

    Wolf, E.A. de

    2002-01-01

    We discuss basic concepts and properties of diffractive phenomena in soft hadron collisions and in deep-inelastic scattering at low Bjorken - x. The paper is not a review of the rapidly developing field but presents an attempt to show in simple terms the close inter-relationship between the dynamics of high-energy hadronic and deep-inelastic diffraction. Using the saturation model of Golec-Biernat and Wuesthoff as an example, a simple explanation of geometrical scaling is presented. The relation between the QCD anomalous multiplicity dimension and the Pomeron intercept is discussed. (author)

  16. Diffraction attraction

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1986-03-15

    Elastic scattering – when colliding particles 'bounce' off each other like billiard balls – has always had a special interest for high energy physicists. While its simplicity makes for deep analogies with classical ideas like diffraction, its jbtle details also test our understanding of the intricate inner mechanisms which drive particle interactions. With a new stock of elastic scattering data now available thanks to experiments at the CERN proton-antiproton Collider, and with studies at higher energies imminent or planned, some seventy physicists gathered in the magnificent chateau at Blois, France, for a 'Workshop on Elastic and Diffractive Scattering at the Collider and Beyond'.

  17. Femtosecond photoelectron point projection microscope

    International Nuclear Information System (INIS)

    Quinonez, Erik; Handali, Jonathan; Barwick, Brett

    2013-01-01

    By utilizing a nanometer ultrafast electron source in a point projection microscope we demonstrate that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained. The duration of the emission process of the photoemitted electrons used to make images is shown to be of the order of 100 fs using an autocorrelation technique. The compact geometry of this photoelectron point projection microscope does not preclude its use as a simple ultrafast electron microscope, and we use simple analytic models to estimate temporal resolutions that can be expected when using it as a pump-probe ultrafast electron microscope. These models show a significant increase in temporal resolution when comparing to ultrafast electron microscopes based on conventional designs. We also model the microscopes spectroscopic abilities to capture ultrafast phenomena such as the photon induced near field effect

  18. Photoelectron Spectroscopy of Substituted Phenylnitrenes

    Science.gov (United States)

    Wijeratne, Neloni R.; Da Fonte, Maria; Wenthold, Paul G.

    2009-06-01

    Nitrenes are unusual molecular structures with unfilled electronic valences that are isoelectronic with carbenes. Although, both can be generated by either thermal or photochemical decomposition of appropriate precursors they usually exhibit different reactivities. In this work, we carry out spectroscopic studies of substituted phenylnitrene to determine how the introduction of substituents will affect the reactivity and its thermochemical properties. All studies were carried out by using the newly constructed time-of-flight negative ion photoelectron spectrometer (NIPES) at Purdue University. The 355 nm photoelectron spectra of the o-, m-, and p-chlorophenyl nitrene anions are fairly similar to that measured for phenylnitrene anion. All spectra show low energy triplet state and a high energy singlet state. The singlet state for the meta isomer is well-resolved, with a well defined origin and observable vibrational structure. Whereas the singlet states for the ortho and para isomers have lower energy onsets and no resolved structure. The isomeric dependence suggests that the geometry differences result from the resonance interaction between the nitrogen and the substituent. Quinoidal resonance structures are possible for the open-shell singlet states of the o- and p-chlorinated phenyl nitrenes. The advantages of this type of electronic structures for the open-shell singlet states is that the unpaired electrons can be more localized on separate atoms in the molecules, minimizing the repulsion between. Because the meta position is not in resonance with the nitrenes, substitution at that position should not affect the structure of the open-shell singlet state. The measured electron affinities (EA) of the triplet phenylnitrenes are in excellent agreement with the values predicted by electronic structure calculations. The largest EA, 1.82 eV is found for the meta isomer, with para being the smallest, 1.70 eV.

  19. Powder diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Hart, M.

    1995-12-31

    the importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquitous application in many fields of science and technology. In the first period, until the mid-1940`s, applications were and developed covering broad categories of materials including inorganic materials, minerals, ceramics, metals, alloys, organic materials and polymers. During this formative period, the concept of quantitative phase analysis was demonstrated. In the second period there followed the blossoming of technology and commercial instruments became widely used. The history is well summarized by Parrish and by Langford and Loueer. By 1980 there were probably 10,000 powder diffractometers in routine use, making it the most widely used of all x-ray crystallographic instruments. In the third, present, period data bases became firmly established and sophisticated pattern fitting and recognition software made many aspects of powder diffraction analysis routine. High resolution, tunable powder diffractometers were developed at sources of synchrotron radiation. The tunability of the spectrum made it possible to exploit all the subtleties of x-ray spectroscopy in diffraction experiments.

  20. Powder diffraction

    International Nuclear Information System (INIS)

    Hart, M.

    1995-01-01

    The importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquitous application in many fields of science and technology. In the first period, until the mid-1940's, applications were and developed covering broad categories of materials including inorganic materials, minerals, ceramics, metals, alloys, organic materials and polymers. During this formative period, the concept of quantitative phase analysis was demonstrated. In the second period there followed the blossoming of technology and commercial instruments became widely used. The history is well summarized by Parrish and by Langford and Loueer. By 1980 there were probably 10,000 powder diffractometers in routine use, making it the most widely used of all x-ray crystallographic instruments. In the third, present, period data bases became firmly established and sophisticated pattern fitting and recognition software made many aspects of powder diffraction analysis routine. High resolution, tunable powder diffractometers were developed at sources of synchrotron radiation. The tunability of the spectrum made it possible to exploit all the subtleties of x-ray spectroscopy in diffraction experiments

  1. UV lamp for photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Cardoso, M.J.B.; Landers, R.; Sundaram, V.S.

    1983-01-01

    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 10 8 -10 9 , 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 (N 2 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.) [pt

  2. Restoration of diffracted far field at the output of circular diffraction waveplate

    International Nuclear Information System (INIS)

    Hovhannisyan, D; Margaryan, H; Abrahamyan, V; Hakobyan, N; Tabiryan, N

    2014-01-01

    The light propagation in an anisotropic periodic media, such us circular diffraction waveplate (CDW) by a finite-difference time-domain (FDTD) technique is studied. The FDTD numerical simulation and the subsequent Fourier transform of the diffracted electric near field was been used for study of ability of CDW to diffract a laser beam and simultaneously convert polarization state. The FDTD simulation results used to restore the diffracted electric far field at the CDW output. an abstract

  3. Coincident photoelectron spectroscopy on superconductors

    International Nuclear Information System (INIS)

    Voss, Stefan

    2011-01-01

    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 2 Sr 2 CaCu 2 O 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.

  4. Diffraction gauging

    International Nuclear Information System (INIS)

    Wilkens, P.H.

    1978-01-01

    This system of gauging is now being designed to fit on an Excello NC lathe to measure the form, accuracy, and size of external contoured surfaces as they approach the finish machined size. A template profile of the finished workpiece, but 0.003 in. bigger on radius, will be aligned with the workpiece using a reference diameter and face on the machining fixture to leave a gap between the profile of the template and workpiece. A helium--neon laser beam will be projected through this gap using a rotating retroreflector and a fixed laser. The resulting diffraction pattern produced by the laser beam passing through the template to workpiece gap will be reflected and focused on a fixed diode array via a second retroreflector which moves and remains in optical alignment with the first. These retroreflectors will be rotated about a center that will enable the laser beam, which is shaped in a long slit, to scan the template workpiece gap from the pole to the equator of the workpiece. The characteristic diffraction pattern will be detected by the fixed diode array, and the signal levels from this array will be processed in a mini-computer programmed to produce a best fit through the two minima of the diode signals. The separation of the two minima will yield the size of the workpiece to template gap and this information will be presented to the machine tool operator

  5. Proton diffraction

    International Nuclear Information System (INIS)

    Den Besten, J.L.; Jamieson, D.N.; Allen, L.J.

    1998-01-01

    The Lindhard theory on ion channeling in crystals has been widely accepted throughout ion beam analysis for use in simulating such experiments. The simulations use a Monte Carlo method developed by Barret, which utilises the classical 'billiard ball' theory of ions 'bouncing' between planes or tubes of atoms in the crystal. This theory is not valid for 'thin' crystals where the planes or strings of atoms can no longer be assumed to be of infinite proportions. We propose that a theory similar to that used for high energy electron diffraction can be applied to MeV ions, especially protons, in thin crystals to simulate the intensities of transmission channeling and of RBS spectra. The diffraction theory is based on a Bloch wave solution of the Schroedinger equation for an ion passing through the periodic crystal potential. The widely used universal potential for proton-nucleus scattering is used to construct the crystal potential. Absorption due to thermal diffuse scattering is included. Experimental parameters such as convergence angle, beam tilt and scanning directions are considered in our calculations. Comparison between theory and experiment is encouraging and suggests that further work is justified. (authors)

  6. Photoelectron studies of machined brass surfaces

    Science.gov (United States)

    Potts, A. W.; Merrison, J. P.; Tournas, A. D.; Yacoot, A.

    UV photoelectron spectroscopy has been used to determine the surface composition of machined brass. The results show a considerable change between the photoelectron surface composition and the bulk composition of the same sample determined by energy-dispersive X-ray fluorescence. On the surface the lead composition is increased by ˜900 G. This is consistent with the important part that lead is believed to play in improving the machinability of this alloy.

  7. Non-dipole angular anisotropy parameters of photoelectrons from semi-filled shell atoms

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Chernysheva, L V [Ioffe Physical-Technical Institute, St-Petersburg 194021 (Russian Federation)

    2006-11-28

    We present the results of calculations of outer and next to outer shell non-dipole angular anisotropy parameters of photoelectrons for semi-filled shell atoms in the Hartree-Fock (HF) one-electron approximation and in the frame of the spin polarized random phase approximation with exchange (SP RPAE) which takes into account inter-electron correlations. We demonstrate for the first time that this characteristic of the photoionization process is essentially sensitive to whether the photoelectron has the same or opposite spin orientation to that of the semi-filled shell.

  8. Non-dipole angular anisotropy parameters of photoelectrons from semi-filled shell atoms

    International Nuclear Information System (INIS)

    Amusia, M Ya; Chernysheva, L V

    2006-01-01

    We present the results of calculations of outer and next to outer shell non-dipole angular anisotropy parameters of photoelectrons for semi-filled shell atoms in the Hartree-Fock (HF) one-electron approximation and in the frame of the spin polarized random phase approximation with exchange (SP RPAE) which takes into account inter-electron correlations. We demonstrate for the first time that this characteristic of the photoionization process is essentially sensitive to whether the photoelectron has the same or opposite spin orientation to that of the semi-filled shell

  9. Study of the local structure of binary surfaces by electron diffraction (XPS, LEED)

    OpenAIRE

    Gereová, Katarína

    2006-01-01

    Study of local structure of binary surface with usage of ultra-thin film of cerium deposited on a Pd (111) single-crystal surface is presented. X-ray photoelectron spectroscopy and diffraction (XPS, XPD), angle resolved UV photoemission spectroscopy (ARUPS) and low energy electron diffraction (LEED) was used for our investigations. LEED and X-ray excited photoemission intensities results represent a surface-geometrical structure. As well, mapping of ultra-violet photoelectron intensities as a...

  10. Giant spin rotation under quasiparticle-photoelectron conversion: Joint effect of sublattice interference and spin-orbit coupling

    DEFF Research Database (Denmark)

    Kuemmeth, Ferdinand; Rashba, E I

    2009-01-01

    Spin- and angular-resolved photoemission spectroscopy is a basic experimental tool for unveiling spin polarization of electron eigenstates in crystals. We prove, by using spin-orbit coupled graphene as a model, that photoconversion of a quasiparticle inside a crystal into a photoelectron can...... be accompanied with a dramatic change in its spin polarization, up to a total spin flip. This phenomenon is typical of quasiparticles residing away from the Brillouin-zone center and described by higher rank spinors and results in exotic patterns in the angular distribution of photoelectrons....

  11. Birefringent coherent diffraction imaging

    Science.gov (United States)

    Karpov, Dmitry; dos Santos Rolo, Tomy; Rich, Hannah; Kryuchkov, Yuriy; Kiefer, Boris; Fohtung, E.

    2016-10-01

    Directional dependence of the index of refraction contains a wealth of information about anisotropic optical properties in semiconducting and insulating materials. Here we present a novel high-resolution lens-less technique that uses birefringence as a contrast mechanism to map the index of refraction and dielectric permittivity in optically anisotropic materials. We applied this approach successfully to a liquid crystal polymer film using polarized light from helium neon laser. This approach is scalable to imaging with diffraction-limited resolution, a prospect rapidly becoming a reality in view of emergent brilliant X-ray sources. Applications of this novel imaging technique are in disruptive technologies, including novel electronic devices, in which both charge and spin carry information as in multiferroic materials and photonic materials such as light modulators and optical storage.

  12. Photoelectron spectroscopy of supersonic molecular beams

    International Nuclear Information System (INIS)

    Pollard, J.E.

    1982-05-01

    A new technique for performing high resolution molecular photoelectron spectroscopy is described, beginning with its conceptual development, through the construction of a prototypal apparatus, to the initial applications on a particularly favorable molecular system. The distinguishing features of this technique are: (1) the introduction of the sample in the form of a collimated supersonic molecular beam; and (2) the use of an electrostatic deflection energy analyzer which is carefully optimized in terms of sensitivity and resolution. This combination makes it possible to obtain photoelectron spectra at a new level of detail for many small molecules. Three experiments are described which rely on the capability to perform rotationally-resolved photoelectron spectroscopy on the hydrogen molecule and its isotopes. The first is a measurement of the ionic vibrational and rotational spectroscopic constants and the vibrationally-selected photoionization cross sections. The second is a determination of the photoelectron asymmetry parameter, β, for selected rotational transitions. The third is an investigation of the rotational relaxation in a free jet expansion, using photoelectron spectroscopy as a probe of the rotational state population distributions. In the closing chapter an assessment is made of the successes and limitations of the technique, and an indication is given of areas for further improvement in future spectrometers

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

    International Nuclear Information System (INIS)

    Allen, G.C.; Holmes, N.R.

    1986-10-01

    Other authors have presented evidence to show that the oxidised surface layer which forms on UO 2 at 25 0 C is amorphous UO 3 . In the present study X-ray photoelectron spectroscopy, infra-red spectroscopy and X-ray diffraction have been used to characterise the higher oxides α-UO 3 , β-UO 3 , γ-UO 3 and δ-UO 3 . While the infra-red and X-ray diffraction results may be used to characterise each oxide the X-ray photoelectron spectra for each phase are very similar. During reduction of the oxide surface in the spectrometer changes in the spectra were observed which were shown to be associated with particular oxidation states of the metal rather than different uranium atom coordination sites within the oxide. A close structural relationship is demonstrated between these oxides and the product at the surface of air-oxidised UO 2 fuel. (author)

  14. Doubly differential diffraction at a time grating in above-threshold ionization: Intracycle and intercycle interferences

    Energy Technology Data Exchange (ETDEWEB)

    Arbo, Diego G., E-mail: diego@iafe.uba.ar [Institute for Astronomy and Space Physics, IAFE (CONICET-UBA), CC 67, Suc. 28 (1428) Buenos Aires (Argentina); Ishikawa, Kenichi L. [Photon Science Center, Graduate School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan); Persson, Emil; Burgdoerfer, Joachim [Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrass e 8-10/136, A-1040 Vienna (Austria)

    2012-05-15

    We analyze the doubly differential electron distribution in atomic above-threshold ionization by a linearly-polarized short-laser pulse. We generalize the one-dimensional (1D) simple man's model (SMM) of Arbo et al. , to a three dimensional (3D) description by using the saddle-point approximation (SPA). We prove that the factorization of the photoelectron spectrum in terms of intracycle and intercycle interference patterns can be extended to the doubly differential momentum distribution. Intercycle interference corresponds to the well-known ATI peaks of the photoelectron spectrum arising from the superposition of electron trajectories released at complex times during different optical cycles, whereas intracycle interference comes from the coherent superposition of trajectories released within the same optical cycle. We verify the SPA predictions by comparison with time-dependent distorted wave calculations and the solutions of the full 3D time-dependent Schroedinger equation (TDSE). An analytical expression for the complete interference pattern within the SPA is presented showing excellent agreement with the numerical calculations. We show that the recently proposed semiclassical description based on the SMM in terms of a diffraction process at a time grating remains unchanged when considering the full 3D problem within the SPA.

  15. Performance of the SRRC scanning photoelectron microscope

    Science.gov (United States)

    Hong, I.-H.; Lee, T.-H.; Yin, G.-C.; Wei, D.-H.; Juang, J.-M.; Dann, T.-E.; Klauser, R.; Chuang, T. J.; Chen, C. T.; Tsang, K.-L.

    2001-07-01

    A scanning photoelectron microscope has been constructed at SRRC. This SPEM system consists primarily of a Fresnel zone plate (ZP) with an order-selection aperture, a flexure scanning stage, a hemispherical electron analyzer, and sample/ZP insertion system. The flexure stage is used to scan the sample. A hemispherical analyzer with Omni V lens and a 16-channel multichannel detector (MCD) is used to collect photoelectrons. A set of 16 photoelectron images at different kinetic energies can be simultaneously acquired in one single scan. The data acquisition system is designed to collect up to 32 images concurrently, including 16 MCD signals, total electron yield and transmitted photon flux. The design and some initial test results of this SPEM station are presented and discussed.

  16. Performance of the SRRC scanning photoelectron microscope

    International Nuclear Information System (INIS)

    Hong, I.-H.; Lee, T.-H.; Yin, G.-C.; Wei, D.-H.; Juang, J.-M.; Dann, T.-E.; Klauser, R.; Chuang, T.J.; Chen, C.T.; Tsang, K.-L.

    2001-01-01

    A scanning photoelectron microscope has been constructed at SRRC. This SPEM system consists primarily of a Fresnel zone plate (ZP) with an order-selection aperture, a flexure scanning stage, a hemispherical electron analyzer, and sample/ZP insertion system. The flexure stage is used to scan the sample. A hemispherical analyzer with Omni V lens and a 16-channel multichannel detector (MCD) is used to collect photoelectrons. A set of 16 photoelectron images at different kinetic energies can be simultaneously acquired in one single scan. The data acquisition system is designed to collect up to 32 images concurrently, including 16 MCD signals, total electron yield and transmitted photon flux. The design and some initial test results of this SPEM station are presented and discussed

  17. Performance of the SRRC scanning photoelectron microscope

    CERN Document Server

    Hong, I H; Yin, G C; Wei, D H; Juang, J M; Dann, T E; Klauser, R; Chuang, T J; Chen, C T; Tsang, K L

    2001-01-01

    A scanning photoelectron microscope has been constructed at SRRC. This SPEM system consists primarily of a Fresnel zone plate (ZP) with an order-selection aperture, a flexure scanning stage, a hemispherical electron analyzer, and sample/ZP insertion system. The flexure stage is used to scan the sample. A hemispherical analyzer with Omni V lens and a 16-channel multichannel detector (MCD) is used to collect photoelectrons. A set of 16 photoelectron images at different kinetic energies can be simultaneously acquired in one single scan. The data acquisition system is designed to collect up to 32 images concurrently, including 16 MCD signals, total electron yield and transmitted photon flux. The design and some initial test results of this SPEM station are presented and discussed.

  18. Photoelectron spectroscopic and microspectroscopic probes of ferroelectrics

    Science.gov (United States)

    Tǎnase, Liviu C.; Abramiuc, Laura E.; Teodorescu, Cristian M.

    2017-12-01

    This contribution is a review of recent aspects connected with photoelectron spectroscopy of free ferroelectric surfaces, metals interfaced with these surfaces, graphene-like layers together with some exemplifications concerning molecular adsorption, dissociations and desorptions occurring from ferroelectrics. Standard photoelectron spectroscopy is used nowadays in correlation with other characterization techniques, such as piezoresponse force microscopy, high resolution transmission electron spectroscopy, and ferroelectric hysteresis cycles. In this work we will concentrate mainly on photoelectron spectroscopy and spectro-microscopy characterization of ferroelectric thin films, starting from atomically clean ferroelectric surfaces of lead zirco-titanate, then going towards heterostructures using this material in combination with graphene-like carbon layers or with metals. Concepts involving charge accumulation and depolarization near surface will be revisited by taking into account the newest findings in this area.

  19. Calculated characteristics of multichannel photoelectron multipliers

    International Nuclear Information System (INIS)

    Vasil'chenko, V.G.; Dajkovskij, A.G.; Milova, N.V.; Rakhmatov, V.E.; Rykalin, V.I.

    1990-01-01

    Structural features and main calculated characteristics of some modifications of position-sensitive two-coordinate multichannel photoelectron multipliers (PEM) with plate-type multiplying systems are described. The presented PEM structures are free from direct optical and ion feedbacks, provide coordinate resolution ≅ 1 mm with efficiency of photoelectron detection ≅ 90%. Capabilities for using silicon field-effect photocathodes, providing electron extraction into vacuum, as well as prospects of using multichannel multiplying systems for readout of the data from solid detectors are considered

  20. a near ambient pressure UV photoelectron spectroscopy

    Indian Academy of Sciences (India)

    Manoj Kumar Ghosalya

    2018-03-02

    Mar 2, 2018 ... UV photoelectron spectroscopy (NAP-UPS) investigations. MANOJ KUMAR ... gations led to various models of Ag-O2 interaction to explain its role in the .... charge lamp (for He I and He II excitations) are available as photon ...

  1. Photoelectron spectroscopy of heavy atoms and molecules

    International Nuclear Information System (INIS)

    White, M.G.

    1979-07-01

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

  2. Nondipole effects in attosecond photoelectron streaking

    DEFF Research Database (Denmark)

    Spiewanowski, Maciek; Madsen, Lars Bojer

    2012-01-01

    The influence of nondipole terms on the time delay in photoionization by an extreme-ultraviolet attosecond pulse in the presence of a near-infrared femtosecond laser pulse from 1s, 2s, and 2p states in hydrogen is investigated. In this attosecond photoelectron streaking process, the relative...

  3. Photoelectron spectroscopy of phosphites and phosphates

    Energy Technology Data Exchange (ETDEWEB)

    Chattopadhyay, S.; Findley, G.L.; McGlynn, S.P.

    1981-01-01

    The ultraviolet photoelectron spectra (UPS) of trimethyl and triethyl phosphite, trimethyl and triethyl phosphate and four substituted phosphates are presented. Assignments are based on analogies to the UPS of phosphorus trichloride and phosphoryl trichloride and are substantiated by CNDO/2 computations. The mechanisms of P-O (axial) bond formation is discussed.

  4. Conformational effects in photoelectron circular dichroism

    Science.gov (United States)

    Turchini, S.

    2017-12-01

    Photoelectron circular dichroism (PECD) is a novel type of spectroscopy, which presents surprising sensitivity to conformational effects in chiral systems. While classical photoelectron spectroscopy mainly responds to conformational effects in terms of energy level shifts, PECD provides a rich and detailed response to tiny changes in electronic and structural properties by means of the intensity dispersion of the circular dichroism as a function of photoelectron kinetic energy. In this work, the basics of PECD will be outlined, emphasizing the role of interference from the l,l+/- 1 outgoing partial wave of the photoelectron in the PECD transition matrix element, which is responsible for the extreme sensitivity to conformational effects. Examples using molecular systems and interfaces will shed light on the powerful application of PECD to classical conformational effects such as group substitution, isomerism, conformer population and clustering. Moreover, the PECD results will be reported in challenging new fields where conformations play a key role, such as vibrational effects, transient chirality and time- resolved experiments. To date, PECD has mostly been based on synchrotron radiation facilities, but it also has a future as a table-top lab experiment by means of multiphoton ionization. An important application of PECD as an analytical tool will be reported. The aim of this review is to illustrate that in PECD, the presence of conformational effects is essential for understanding a wide range of effects from a new perspective, making it different from classical spectroscopy.

  5. Threshold photoelectron spectroscopy of acetaldehyde and acrolein

    International Nuclear Information System (INIS)

    Yencha, Andrew J.; Siggel-King, Michele R.F.; King, George C.; Malins, Andrew E.R.; Eypper, Marie

    2013-01-01

    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

  6. 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…

  7. Near threshold behavior of photoelectron satellite intensities

    International Nuclear Information System (INIS)

    Shirley, D.A.; Becker, U.; Heimann, P.A.; Langer, B.

    1987-09-01

    The historical background and understanding of photoelectron satellite peaks is reviewed, using He(n), Ne(1s), Ne(2p), Ar(1s), and Ar(3s) as case studies. Threshold studies are emphasized. The classification of electron correlation effects as either ''intrinsic'' or ''dynamic'' is recommended. 30 refs., 7 figs

  8. Development of hard X-ray photoelectron SPLEED-based spectrometer applicable for probing of buried magnetic layer valence states

    Energy Technology Data Exchange (ETDEWEB)

    Kozina, Xeniya, E-mail: kozina@uni-mainz.de [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Viol Barbosa, Carlos Eduardo; Ouardi, Siham; Karel, Julie [Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden (Germany); Yamamoto, Masafumi [Division of Electronics for Informatics, Hokkaido University, Sapporo 060-0814 (Japan); Kobayashi, Keisuke [Japan Atomic Energy Agency, SPring-8, Hyogo 679-5148 (Japan); Elmers, Hans Joachim; Schönhense, Gerd [Institut für Physik, Johannes Gutenberg – Universität, 55099 Mainz (Germany); Felser, Claudia [Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden (Germany)

    2016-08-15

    Highlights: • A high-voltage compatible spin-HAXPES detector based on SPLEED from W(001) has been developed. • Magnetic properties of a TMR device were studied by core-level photoemission on the Fe 2p{sub 3/2} states. • The developed instrument enabled probing of buried layers in the region of the valence states. - Abstract: A novel design of high-voltage compatible polarimeter for spin-resolved hard X-ray photoelectron spectroscopy (Spin-HAXPES) went into operation at beamline BL09XU of SPring-8 in Hyogo, Japan. The detector is based on the well-established principle of electron diffraction from a W(001) single-crystal at a scattering energy of 103.5 eV. It's special feature is that it can be operated at a high negative bias potential up to 10 kV, necessary to access the HAXPES range. The polarimeter is operated behind a large hemispherical analyzer (Scienta R-4000). It was optimized for high transmission of the transfer optics. A delay-line detector (20 mm dia.) is positioned at the exit plane of the analyzer enabling conventional multichannel intensity spectroscopy simultaneously with single-channel spin analysis. The performance of the combined setup is demonstrated by the spin-resolved data for the valence-region of a FeCo functional layer of a tunneling device, buried beneath 3 nm of oxidic material. The well-structured spin polarization spectrum validates Spin-HAXPES in the valence energy range as powerful method for bulk electronic structure analysis. The spin polarization spectrum exhibits a rich structure, originating from clearly discernible transitions in the majority and minority partial spin spectra.

  9. 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.

  10. Classical ultraviolet photoelectron spectroscopy of polymers

    International Nuclear Information System (INIS)

    Salaneck, W.R.

    2009-01-01

    Although X-ray photoelectron spectroscopy of polymers was well established by Clark and coworkers in the 1970s, ultraviolet photoelectron spectroscopy of polymer films, was developed later. Previous to the 1970s, the first attempts to use ultraviolet light on polymer films took the form of appearance potential (valence band edge) measurements. Only some years later could the full valence band region of thin polymer films, including insulating polymers, semiconducting polymers and electrically conducting polymers. The development of what might be termed 'classical ultraviolet photoelectron spectroscopy' of polymer films may be loosely based upon a variety of issues, including adapting thin polymer film technology to ultra high vacuum studies, the widespread use of helium resonance lamps for studies of solid surfaces, the combined advent of practical and sufficient theoretical-computational methods. The advent of, and the use of, easily available synchrotron radiation for multi-photon spectroscopies, nominally in the area of the near UV, is not included in the term 'classical'. At the same time, electrically conducting polymers were discovered, leading to applications of the corresponding semiconducting polymers, which added technologically driven emphasis to this development of ultraviolet photoelectron spectroscopy for polymer materials. This paper traces a limited number of highlights in the evolution of ultraviolet photoelectron spectroscopy of polymers, from the 1970s through to 2008. Also, since this issue is dedicated to Prof. Kazuhiko Seki, who has been a friend and competitor for over two decades, the author relies on some of Prof. Seki's earlier research, unpublished, on who-did-what-first. Prof. Seki's own contributions to the field, however, are discussed in other articles in this issue.

  11. Polarized neutrons

    International Nuclear Information System (INIS)

    Williams, W.G.

    1988-01-01

    The book on 'polarized neutrons' is intended to inform researchers in condensed matter physics and chemistry of the diversity of scientific problems that can be investigated using polarized neutron beams. The contents include chapters on:- neutron polarizers and instrumentation, polarized neutron scattering, neutron polarization analysis experiments and precessing neutron polarization. (U.K.)

  12. Ultraviolet photoelectron spectroscopy of transient species

    International Nuclear Information System (INIS)

    Leeuw, D.M. de.

    1979-01-01

    Transient species are studied in the isolation of the gas phase using ultraviolet photoelectron spectroscopy (PES). A description of the equipment used and a discussion of some theoretical topics, which play a role in the interpretation of PE spectra, are given. Koopmans' theorem, Hartree-Fock-Slater (HFS) calculations and the sum rule are discussed. A versatile ultraviolet PE spectrometer, designed specifically for this purpose, has been built and the construction and performance of this instrument are described. (Auth.)

  13. Anion photoelectron spectroscopy of radicals and clusters

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-12-01

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

  14. 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.

  15. Imaging photoelectron circular dichroism of chiral molecules by femtosecond multiphoton coincidence detection

    Energy Technology Data Exchange (ETDEWEB)

    Lehmann, C. Stefan; Ram, N. Bhargava; Janssen, Maurice H. M., E-mail: m.h.m.janssen@vu.nl [LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Powis, Ivan [School of Chemistry, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2013-12-21

    Here, we provide a detailed account of novel experiments employing electron-ion coincidence imaging to discriminate chiral molecules. The full three-dimensional angular scattering distribution of electrons is measured after photoexcitation with either left or right circular polarized light. The experiment is performed using a simplified photoelectron-photoion coincidence imaging setup employing only a single particle imaging detector. Results are reported applying this technique to enantiomers of the chiral molecule camphor after three-photon ionization by circularly polarized femtosecond laser pulses at 400 nm and 380 nm. The electron-ion coincidence imaging provides the photoelectron spectrum of mass-selected ions that are observed in the time-of-flight mass spectra. The coincident photoelectron spectra of the parent camphor ion and the various fragment ions are the same, so it can be concluded that fragmentation of camphor happens after ionization. We discuss the forward-backward asymmetry in the photoelectron angular distribution which is expressed in Legendre polynomials with moments up to order six. Furthermore, we present a method, similar to one-photon electron circular dichroism, to quantify the strength of the chiral electron asymmetry in a single parameter. The circular dichroism in the photoelectron angular distribution of camphor is measured to be 8% at 400 nm. The electron circular dichroism using femtosecond multiphoton excitation is of opposite sign and about 60% larger than the electron dichroism observed before in near-threshold one-photon ionization with synchrotron excitation. We interpret our multiphoton ionization as being resonant at the two-photon level with the 3s and 3p Rydberg states of camphor. Theoretical calculations are presented that model the photoelectron angular distribution from a prealigned camphor molecule using density functional theory and continuum multiple scattering X alpha photoelectron scattering calculations

  16. Nondipole effects in the angular distribution of photoelectrons from the C K shell of the CO molecule

    International Nuclear Information System (INIS)

    Hosaka, K.; Teramoto, T.; Adachi, J.; Yagishita, A.; Golovin, A. V.; Takahashi, M.; Watanabe, N.; Jahnke, T.; Weber, Th.; Schoeffler, M.; Schmidt, L.; Jagutzki, O.; Schmidt-Boecking, H.; Doerner, R.; Osipov, T.; Prior, M. H.; Landers, A. L.; Semenov, S. K.; Cherepkov, N. A.

    2006-01-01

    Measurements and calculations of a contribution of the nondipole terms in the angular distribution of photoelectrons from the C K shell of randomly oriented CO molecules are reported. In two sets of measurements, the angular distribution in the plane containing the photon polarization and the photon momentum vectors of linearly polarized radiation and the full three-dimensional photoelectron momentum distribution after absorption of circularly polarized light have been measured. Calculations have been performed in the relaxed core Hartree-Fock approximation with a fractional charge. Both theory and experiment show that the nondipole terms are very small in the photon energy region from the ionization threshold of the K shell up to about 70 eV above it

  17. Ambipolar Electric Field, Photoelectrons, and Their Role in Atmospheric Escape From Hot Jupiters

    Science.gov (United States)

    Cohen, O.; Glocer, A.

    2012-01-01

    Atmospheric mass loss from Hot Jupiters can be large due to the close proximity of these planets to their host star and the strong radiation the planetary atmosphere receives. On Earth, a major contribution to the acceleration of atmospheric ions comes from the vertical separation of ions and electrons, and the generation of the ambipolar electric field. This process, known as the "polar wind," is responsible for the transport of ionospheric constituents to Earth's magnetosphere, where they are well observed. The polar wind can also be enhanced by a relatively small fraction of super-thermal electrons (photoelectrons) generated by photoionization.We formulate a simplified calculation of the effect of the ambipolar electric field and the photoelectrons on the ion scale height in a generalized manner. We find that the ion scale height can be increased by a factor of 2-15 due to the polar wind effects. We also estimate a lower limit of an order of magnitude increase of the ion density and the atmospheric mass-loss rate when polar wind effects are included.

  18. Alkyl-terminated Si(111) surfaces: A high-resolution, core level photoelectron spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Terry, J.; Linford, M.R.; Wigren, C.; Cao, R.; Pianetta, P.; Chidsey, C.E. [Stanford University, Stanford, California 94309 (United States)

    1999-01-01

    The bonding of alkyl monolayers to Si(111) surfaces has been studied with high-resolution core level photoelectron spectroscopy (PES). Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) Olefin insertion into the H{endash}Si bond of the H{endash}Si(111) surface, and (ii) replacement of Cl on the Cl{endash}Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, PES has revealed a C 1s component shifted to lower binding energy and a Si 2p component shifted to higher binding energy. Both components are attributed to the presence of a C{endash}Si bond at the interface. Along with photoelectron diffraction data [Appl. Phys. Lett. {bold 71}, 1056, (1997)], these data are used to show that these two synthetic methods can be used to functionalize the Si(111) surface. {copyright} {ital 1999 American Institute of Physics.}

  19. Diffraction coherence in optics

    CERN Document Server

    Françon, M; Green, L L

    2013-01-01

    Diffraction: Coherence in Optics presents a detailed account of the course on Fraunhofer diffraction phenomena, studied at the Faculty of Science in Paris. The publication first elaborates on Huygens' principle and diffraction phenomena for a monochromatic point source and diffraction by an aperture of simple form. Discussions focus on diffraction at infinity and at a finite distance, simplified expressions for the field, calculation of the path difference, diffraction by a rectangular aperture, narrow slit, and circular aperture, and distribution of luminous flux in the airy spot. The book th

  20. The threshold photoelectron spectrum of mercury

    International Nuclear Information System (INIS)

    Rojas, H; Dawber, G; Gulley, N; King, G C; Bowring, N; Ward, R

    2013-01-01

    The threshold photoelectron spectrum of mercury has been recorded over the energy range (10–40 eV) which covers the region from the lowest state of the singly charged ion, 5d 10 6s( 2 S 1/2 ), to the double charged ionic state, 5d 9 ( 2 D 3/2 )6s( 1 D 2 ). Synchrotron radiation has been used in conjunction with the penetrating-field threshold-electron technique to obtain the spectrum with high resolution. The spectrum shows many more features than observed in previous photoemission measurements with many of these assigned to satellite states converging to the double ionization limit. (paper)

  1. Photoelectron holography with improved image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Matsushita, Tomohiro, E-mail: matusita@spring8.or.j [Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun Hyogo 679-5198 (Japan); Matsui, Fumihiko; Daimon, Hiroshi [Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Hayashi, Kouichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2010-05-15

    Electron holography is a type of atomic structural analysis, and it has unique features such as element selectivity and the ability to analyze the structure around an impurity in a crystal. In this paper, we introduce the measurement system, electron holograms, a theory for the recording process of an electron hologram, and a theory for the reconstruction algorithm. We describe photoelectron holograms, Auger electron holograms, and the inverse mode of an electron hologram. The reconstruction algorithm, scattering pattern extraction algorithm (SPEA), the SPEA with maximum entropy method (SPEA-MEM), and SPEA-MEM with translational operation are also described.

  2. Photoelectron holography with improved image reconstruction

    International Nuclear Information System (INIS)

    Matsushita, Tomohiro; Matsui, Fumihiko; Daimon, Hiroshi; Hayashi, Kouichi

    2010-01-01

    Electron holography is a type of atomic structural analysis, and it has unique features such as element selectivity and the ability to analyze the structure around an impurity in a crystal. In this paper, we introduce the measurement system, electron holograms, a theory for the recording process of an electron hologram, and a theory for the reconstruction algorithm. We describe photoelectron holograms, Auger electron holograms, and the inverse mode of an electron hologram. The reconstruction algorithm, scattering pattern extraction algorithm (SPEA), the SPEA with maximum entropy method (SPEA-MEM), and SPEA-MEM with translational operation are also described.

  3. X-Ray Photoelectron Spectroscopic Characterization of Iron Oxide Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Radu, T., E-mail: Teodora.Radu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293, Cluj Napoca (Romania); Iacovita, C. [Department of Pharmaceutical Physics-Biophysics, Faculty of Pharmacy, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400349, Cluj-Napoca (Romania); Benea, D. [Faculty of Physics, Babes Bolyai University, 400271, Cluj-Napoca (Romania); Turcu, R. [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293, Cluj Napoca (Romania)

    2017-05-31

    Highlights: • Characterization of three types of iron oxides magnetic nanoparticles. • A correlation between valence band XPS and the degree of iron oxidation is proposed. • Theoretical contributions of Fe in tetragonal and octahedral environment are shown. - Abstract: We report X-ray photoelectron spectroscopy (XPS) results on iron oxide magnetic nanoparticle (Fe{sub 3}O{sub 4}) synthesized using solvothermal reduction in the presence of polyethylene glycol. The magnetite obtained was employed as precursor for the synthesis of γ-Fe{sub 2}O{sub 3} (by oxygen dissociation) which in turn was transformed into α-Fe{sub 2}O{sub 3}. We confirmed the magnetite, maghemite and hematite structure by Fourier Transformed Spectroscopy (FTIR) and X-ray diffraction (XRD). The analysis of the XPS core level and valence band (VB) photoemission spectra for all investigated samples is discussed in terms of the degree of iron oxidation. This is of fundamental importance to better understand the electronic structure of the obtained iron oxide nanoparticles in order to control and improve their quality for specific biomedical applications. Moreover, theoretical band structure calculations are performed for magnetite and the separate contributions of Fe in tetragonal and octahedral environment are shown.

  4. Coulomb-free and Coulomb-distorted recolliding quantum orbits in photoelectron holography

    Science.gov (United States)

    Maxwell, A. S.; Figueira de Morisson Faria, C.

    2018-06-01

    We perform a detailed analysis of the different types of orbits in the Coulomb quantum orbit strong-field approximation (CQSFA), ranging from direct to those undergoing hard collisions. We show that some of them exhibit clear counterparts in the standard formulations of the strong-field approximation for direct and rescattered above-threshold ionization, and show that the standard orbit classification commonly used in Coulomb-corrected models is over-simplified. We identify several types of rescattered orbits, such as those responsible for the low-energy structures reported in the literature, and determine the momentum regions in which they occur. We also find formerly overlooked interference patterns caused by backscattered Coulomb-corrected orbits and assess their effect on photoelectron angular distributions. These orbits improve the agreement of photoelectron angular distributions computed with the CQSFA with the outcome of ab initio methods for high energy phtotoelectrons perpendicular to the field polarization axis.

  5. Phase behavior in diffraction

    International Nuclear Information System (INIS)

    Checon, A.

    1983-01-01

    Theoretical formulation of a straight edge diffraction shows a phase difference of π/2 between the incoming and diffracted waves. Experiments using two straight edges do not confirm the π/2 difference but suggest that the incoming wave is in phase with the wave diffracted into the shadowed region of the edge and out of phase by a factor of π with the wave diffracted into the illuminated region. (Author) [pt

  6. Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

    Science.gov (United States)

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

    2016-05-05

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

  7. Photoelectron spectroscopy of supersonic molecular beams

    International Nuclear Information System (INIS)

    Pollard, J.E.; Trevor, D.J.; Lee, Y.T.; Shirley, D.A.

    1981-01-01

    A high-resolution photoelectron spectrometer which uses molecular beam sampling is described. Photons from a rare-gas resonance lamp or UV laser are crossed with the beam from a differentially pumped supersonic nozzle source. The resulting photoelectrons are collected by an electrostatic analyzer of a unique design consisting of a 90 0 spherical sector preanalyzer, a system of lenses, and a 180 0 hemispherical deflector. A multichannel detection system based on dual microchannel plates with a resistive anode position encoder provides an increase in counting efficiency by a factor of 12 over the equivalent single channel detector. The apparatus has demonstrated an instrumental resolution of better than 10 meV FWHM, limited largely by the photon source linewidth. A quadrupole mass spectrometer is used to characterize the composition of the molecular beam. Extensive differential pumping is provided to protect the critical surfaces of the analyzer and mass spectrometer from contamination. Because of the near elimination of Doppler and rotational broadenings, the practical resolution is the highest yet obtained in molecular PES

  8. Neutron Larmor diffraction measurements for materials science

    International Nuclear Information System (INIS)

    Repper, J.; Keller, T.; Hofmann, M.; Krempaszky, C.; Petry, W.; Werner, E.

    2010-01-01

    Neutron Larmor diffraction (LD) is a high-resolution diffraction technique based on the Larmor precession of polarized neutrons. In contrast to conventional diffraction, LD does not depend on the accurate measurement of Bragg angles, and thus the resolution is independent of the beam collimation and monochromaticity. At present, a relative resolution for the determination of the crystal lattice spacing d of Δd/d∼10 -6 is achieved, i.e. at least one order of magnitude superior to conventional neutron or X-ray techniques. This work is a first step to explore the application of LD to high-resolution problems in the analysis of residual stresses, where both the accurate measurement of absolute d values and the possibility of measuring type II and III stresses may provide additional information beyond those accessible by conventional diffraction techniques. Data obtained from Inconel 718 samples are presented.

  9. Neutron Larmor diffraction measurements for materials science

    Energy Technology Data Exchange (ETDEWEB)

    Repper, J., E-mail: julia_repper@web.de [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU Muenchen, 85747 Garching (Germany); Keller, T. [Max-Planck-Institut fuer Festkoerperforschung, 70569 Stuttgart (Germany)] [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU Muenchen, 85747 Garching (Germany); Hofmann, M. [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU Muenchen, 85747 Garching (Germany); Krempaszky, C. [Christian-Doppler-Labor fuer Werkstoffmechanik von Hochleistungslegierungen, TU Muenchen, 85747 Garching (Germany); Petry, W. [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU Muenchen, 85747 Garching (Germany); Werner, E. [Lehrstuhl fuer Werkstoffkunde und Werkstoffmechanik, TU Muenchen, 85747 Garching (Germany)

    2010-05-15

    Neutron Larmor diffraction (LD) is a high-resolution diffraction technique based on the Larmor precession of polarized neutrons. In contrast to conventional diffraction, LD does not depend on the accurate measurement of Bragg angles, and thus the resolution is independent of the beam collimation and monochromaticity. At present, a relative resolution for the determination of the crystal lattice spacing d of {Delta}d/d{approx}10{sup -6} is achieved, i.e. at least one order of magnitude superior to conventional neutron or X-ray techniques. This work is a first step to explore the application of LD to high-resolution problems in the analysis of residual stresses, where both the accurate measurement of absolute d values and the possibility of measuring type II and III stresses may provide additional information beyond those accessible by conventional diffraction techniques. Data obtained from Inconel 718 samples are presented.

  10. Neutron diffraction studies of thin film multilayer structures

    International Nuclear Information System (INIS)

    Majkrzak, C.F.

    1985-01-01

    The application of neutron diffraction methods to the study of the microscopic chemical and magnetic structures of thin film multilayers is reviewed. Multilayer diffraction phenomena are described in general and in particular for the case in which one of the materials of a bilayer is ferromagnetic and the neutron beam polarized. Recent neutron diffraction measurements performed on some interesting multilayer systems are discussed. 70 refs., 5 figs

  11. Surface characterization of colossal magnetoresistive manganites La1-xSr xMnO3 using photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Mannella, N.; Rosenhahn, A.; Nambu, A.; Sell, B.C.; Mun, B.S.; Yang, S.-H.; Marchesini, S.; Watanabe, M.; Ibrahim, K.; Ritchey, S.B.; Tomioka, Y.; Fadley, C.S.

    2006-01-01

    We have studied the temperature and time dependence of Surface chemical composition and atomic structure of in situ fractured colossal magnetoresistive perovskites La 1-x Sr x MnO (x = 0.3, 0.4) using core-level photoelectron spectroscopy and diffraction, simultaneous with observing marked changes in both core and valence electronic structure on going above the Curie temperature [N. Mannella et al., Phys. Rev. Lett. 92 (2004) 166401]. Stoichiometric analyses via core-level intensity ratios show that the near-surface composition is very nearly the same as that of the nominal (bulk) stoichiometry and further show that, during duration of our experiments, the degree of surface stoichiometry alteration or contamination has been minimal. The effects of photoelectron diffraction on such analyses are also explored. We comment on the degree to which near-surface composition or atomic-structure alterations might influence spectroscopic investigations of these manganites, or other strongly correlated materials

  12. Spectroscopic imaging, diffraction, and holography with x-ray photoemission

    International Nuclear Information System (INIS)

    1992-02-01

    X-ray probes are capable of determining the spatial structure of an atom in a specific chemical state, over length scales from about a micron all the way down to atomic resolution. Examples of these probes include photoemission microscopy, energy-dependent photoemission diffraction, photoelectron holography, and X-ray absorption microspectroscopy. Although the method of image formation, chemical-state sensitivity, and length scales can be very different, these X-ray techniques share a common goal of combining a capability for structure determination with chemical-state specificity. This workshop will address recent advances in holographic, diffraction, and direct imaging techniques using X-ray photoemission on both theoretical and experimental fronts. A particular emphasis will be on novel structure determinations with atomic resolution using photoelectrons

  13. Spectroscopic imaging, diffraction, and holography with x-ray photoemission

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-01

    X-ray probes are capable of determining the spatial structure of an atom in a specific chemical state, over length scales from about a micron all the way down to atomic resolution. Examples of these probes include photoemission microscopy, energy-dependent photoemission diffraction, photoelectron holography, and X-ray absorption microspectroscopy. Although the method of image formation, chemical-state sensitivity, and length scales can be very different, these X-ray techniques share a common goal of combining a capability for structure determination with chemical-state specificity. This workshop will address recent advances in holographic, diffraction, and direct imaging techniques using X-ray photoemission on both theoretical and experimental fronts. A particular emphasis will be on novel structure determinations with atomic resolution using photoelectrons.

  14. Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

    Energy Technology Data Exchange (ETDEWEB)

    Zaliznyak, Igor [Brookhaven National Laboratory (BNL); Savici, Andrei T [ORNL; Garlea, Vasile O [ORNL; Winn, Barry L [ORNL; Schneelock, John [Brookhaven National Laboratory (BNL); Tranquada, John M. [Brookhaven National Laboratory (BNL); Gu, G. D. [Brookhaven National Laboratory (BNL); Wang, Aifeng [Brookhaven National Laboratory (BNL); Petrovic, C [Brookhaven National Laboratory (BNL)

    2017-01-01

    We describe some of the first polarized neutron scattering measurements performed at HYSPEC spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. We discuss details of the instrument setup and the experimental procedures in the mode with the full polarization analysis. Examples of the polarized neutron diffraction and the polarized inelastic neutron data obtained on single crystal samples are presented.

  15. A bromine-based dichroic X-ray polarization analyser

    CERN Document Server

    Collins, S P; Brown, S D; Thompson, P

    2001-01-01

    We have demonstrated the advantages offered by dichroic X-ray polarization filters for linear polarization analysis, and describe such a device, based on a dibromoalkane/urea inclusion compound. The polarizer has been successfully tested by analysing the polarization of magnetic diffraction from holmium.

  16. Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

    OpenAIRE

    Zaliznyak, Igor A; Savici, Andrei T.; Garlea, V. Ovidiu; Winn, Barry; Filges, Uwe; Schneeloch, John; Tranquada, John M.; Gu, Genda; Wang, Aifeng; Petrovic, Cedomir

    2016-01-01

    We describe some of the first polarized neutron scattering measurements performed at HYSPEC spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. We discuss details of the instrument setup and the experimental procedures in the mode with full polarization analysis. Examples of polarized neutron diffraction and polarized inelastic neutron data obtained on single crystal samples are presented.

  17. Atomic quasi-Bragg-diffraction in a magnetic field

    NARCIS (Netherlands)

    Domen, K.F.E.M.; Jansen, M.A.H.M.; Dijk, van W.; Leeuwen, van K.A.H.

    2009-01-01

    We report on a technique to split an at. beam coherently with an easily adjustable splitting angle. In our expt. metastable helium atoms in the |{1s2s}3S1 M=1 state diffract from a polarization gradient light field formed by counterpropagating .sigma.+ and .sigma.- polarized laser beams in the

  18. Atomic photoelectron-spectroscopy studies using synchrotron radiation

    International Nuclear Information System (INIS)

    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

  19. Many-electron effects in photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Martin, R.L.

    1976-06-01

    The deviations from Koopmans' one-electron model of photoionization which lead to satellite structure in the photoelectron spectrum are examined within the formalism of configuration interaction (CI). The mechanisms which contribute to satellite intensity may be classified as continuum state configuration interaction, final ionic state configuration interaction, and initial state configuration interaction. The discussion centers around the last two mechanisms, these being the prime contributors to the satellite intensity well above threshold. Specific examples of theoretical ''spectra'' are presented for the F(1s) region of HF and the 1s region of neon. The agreement between theory and experiment is found to be excellent. In these two instances, initial state configuration interaction contributions increase the satellite intensity and are of nearly equal importance to the final ionic state mixing

  20. Study of niobium oxidation by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Durand, C.

    1985-01-01

    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 (Nb 2 O 5 ) on the metal (Nb). This interface is essentially formed by the monoxide (NbO) and dioxide (NbO 2 ). 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 [fr

  1. Photoelectron spectroscopy of surfaces under humid conditions

    International Nuclear Information System (INIS)

    Bluhm, Hendrik

    2010-01-01

    The interaction of water with surfaces plays a major role in many processes in the environment, atmosphere and technology. Weathering of rocks, adhesion between surfaces, and ionic conductance along surfaces are among many phenomena that are governed by the adsorption of molecularly thin water layers under ambient humidities. The properties of these thin water films, in particular their thickness, structure and hydrogen-bonding to the substrate as well as within the water film are up to now not very well understood. Ambient pressure photoelectron spectroscopy (APXPS) is a promising technique for the investigation of the properties of thin water films. In this article we will discuss the basics of APXPS as well as the particular challenges that are posed by investigations in water vapor at Torr pressures. We will also show examples of the application of APXPS to the study of water films on metals and oxides.

  2. A Photoelectron Spectroscopic Study of Di-t-butylphosphazene

    DEFF Research Database (Denmark)

    Elbel, S.; Ellis, A.; Niecke, E.

    1985-01-01

    Gaseous trans-ButPNBut, generated by mild gas-phase thermolysis of its more stable [2 + 1] cyclodimer, has been characterized by field-ionization mass spectrometry and U.V. photoelectron spectroscopy. The photoelectron spectrum has been assigned based on SCC-Xα model calculations for representat......Gaseous trans-ButPNBut, generated by mild gas-phase thermolysis of its more stable [2 + 1] cyclodimer, has been characterized by field-ionization mass spectrometry and U.V. photoelectron spectroscopy. The photoelectron spectrum has been assigned based on SCC-Xα model calculations...

  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

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

    International Nuclear Information System (INIS)

    Chen Feng; Wu Wen-Bin; Li Shun-Yi; Klein Andreas

    2014-01-01

    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)O 3 (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)

  5. Fundamentals of the physical theory of diffraction

    CERN Document Server

    Ufimtsev, Pyotr Ya

    2014-01-01

    A complete presentation of the modern physical theory of diffraction and its applications, by the world's leading authority on the topicExtensive revisions and additions to the first edition yield a second edition that is 492 pages in length, with 122 figuresNew sections examine the nature of polarization coupling, and extend the theory of shadow radiation and reflection to opaque objectsThis book features end-of-chapter problems and a solutions manual for university professors and graduate studentsMATLAB codes presented in appendices allow for quick numeric calculations of diffracted waves

  6. Diffraction at TOTEM

    OpenAIRE

    Giani, S; Niewiadomski, H; Antchev, G; Aspell, P; Avati, V; Bagliesi, M G; Berardi, V; Berretti, M; Besta, M; Bozzo, M; Brücken, E; Buzzo, A; Cafagna, F; Calicchio, M; Catanesi, M G

    2010-01-01

    The primary objective of the TOTEM experiment at the LHC is the measurement of the total proton-proton cross section with the luminosity-independent method and the study of elastic proton-proton cross-section over a wide |t|-range. In addition TOTEM also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage...

  7. Diffraction at TOTEM

    OpenAIRE

    Antchev, G.; Aspell, P.; Avati, V.; Bagliesi, M.G.; Berardi, V.; Berretti, M.; Bottigli, U.; Bozzo, M.; Brucken, E.; Buzzo, A.; Cafagna, F.; Calicchio, M.; Catanesi, M.G.; Catastini, P.L.; Cecchi, R.

    2008-01-01

    The TOTEM experiment at the LHC measures the total proton-proton cross section with the luminosity-independent method and the elastic proton-proton cross-section over a wide |t|-range. It also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage of the large common rapidity coverage for charged and neutral...

  8. Scaling laws for photoelectron holography in the midinfrared wavelength regime

    NARCIS (Netherlands)

    Huismans, Y.; Gijsbertsen, A.; Smolkowska, A S; Jungmann, J H; Rouz??e, A.; Logman, P. S W M; L??pine, F.; Cauchy, C.; Zamith, S; Marchenko, T; Bakker, Joost M.; Berden, G.; Redlich, B; Van Der Meer, A. F G; Ivanov, M Yu; Yan, T. M.; Bauer, D.; Smirnova, O; Vrakking, M. J J

    2012-01-01

    Midinfrared strong-field laser ionization offers the promise of measuring holograms of atoms and molecules, which contain both spatial and temporal information of the ion and the photoelectron with subfemtosecond temporal and angstrom spatial resolution. We report on the scaling of photoelectron

  9. Scaling Laws for Photoelectron Holography in the Midinfrared Wavelength Regime

    NARCIS (Netherlands)

    Huismans, Y.; Gijsbertsen, A.; Smolkowska, A. S.; Jungmann, J. H.; Rouzee, A.; Logman, Pswm; Lepine, F.; Cauchy, C.; Zamith, S.; Marchenko, T.; Bakker, J. M.; G. Berden,; Redlich, B.; van der Meer, A. F. G.; Ivanov, M. Y.; Yan, T. M.; Bauer, D.; Smirnova, O.; Vrakking, M. J. J.

    2012-01-01

    Midinfrared strong-field laser ionization offers the promise of measuring holograms of atoms and molecules, which contain both spatial and temporal information of the ion and the photoelectron with subfemtosecond temporal and angstrom spatial resolution. We report on the scaling of photoelectron

  10. 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.

  11. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    International Nuclear Information System (INIS)

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

    2015-01-01

    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

  12. 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.

  13. Observables of QCD diffraction

    Science.gov (United States)

    Mieskolainen, Mikael; Orava, Risto

    2017-03-01

    A new combinatorial vector space measurement model is introduced for soft QCD diffraction. The model independent mathematical construction resolves experimental complications; the theoretical framework of the approach includes the Good-Walker view of diffraction, Regge phenomenology together with AGK cutting rules and random fluctuations.

  14. Encapsulation process for diffraction gratings.

    Science.gov (United States)

    Ratzsch, Stephan; Kley, Ernst-Bernhard; Tünnermann, Andreas; Szeghalmi, Adriana

    2015-07-13

    Encapsulation of grating structures facilitates an improvement of the optical functionality and/or adds mechanical stability to the fragile structure. Here, we introduce novel encapsulation process of nanoscale patterns based on atomic layer deposition and micro structuring. The overall size of the encapsulated structured surface area is only restricted by the size of the available microstructuring and coating devices; thus, overcoming inherent limitations of existing bonding processes concerning cleanliness, roughness, and curvature of the components. Finally, the process is demonstrated for a transmission grating. The encapsulated grating has 97.5% transmission efficiency in the -1st diffraction order for TM-polarized light, and is being limited by the experimental grating parameters as confirmed by rigorous coupled wave analysis.

  15. Photoelectron angular distributions from strong-field ionization of oriented molecules

    DEFF Research Database (Denmark)

    Holmegaard, Lotte; Hansen, Jonas Lerche; Kalhøj, Line

    2010-01-01

    The combination of ultrafast light sources with detection of molecular-frame photoelectron angular distributions (MFPADs) is setting new standards for detailed interrogation of molecular dynamics. However, until recently measurement of MFPADs relied on determining the molecular orientation after...... ionization, which is limited to species and processes where ionization leads to fragmentation. An alternative is to fix the molecular frame before ionization. The only demonstrations of such spatial orientation involved aligned small linear nonpolar molecules. Here we extend these techniques to the general...... class of polar molecules. Carbonylsulphide and benzonitrile molecules, fixed in space by combined laser and electrostatic fields, are ionized with intense, circularly polarized 30-fs laser pulses. For carbonylsulphide and benzonitrile oriented in one dimension, the MFPADs exhibit pronounced anisotropies...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-12-01

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

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

    International Nuclear Information System (INIS)

    Zanni, Martin T.

    1999-01-01

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

  18. Laser photoelectron spectrometry of Sc- and Y-

    International Nuclear Information System (INIS)

    Feigerle, C.S.; Herman, Z.; Lineberger, W.C.

    1981-01-01

    The photoelectron spectra of Sc - and Y - have been obtained in a crossed ion- and laser-beam experiment. Analysis of the Sc - spectrum yields two bound terms of 3d4s 2 4p configuration ( 1 D 0 and 3 D 0 ), with EA(Sc) = 0.189 +- 0.020 eV and an excited-state binding energy of 0.042 +- 0.020 eV. Similarly, the (4d5s 2 5p) 1 D 0 ground state of Y - is bound by 0.308 +- 0.012 eV and a (4d5s 2 5p) 3 D 0 excited term is bound by 0.165 +- 0.025 eV. With the determination of the bound electronic configuration of Sc - as 3d4s 2 4p, the order of filling of electron shells of the first transition series negative ions is found to be 4s 2 ep, 3d4s 2 4p, the order of filling of electron shells of the first transition series negative ions is found to be 4s 2 4p, 3d4s 2 4p, followed by 3dsup(k) 4s 2 (k = 3, 4, ..., 10). (orig.)

  19. Photoelectron spectroscopy of the 6-azauracil anion.

    Science.gov (United States)

    Chen, Jing; Buonaugurio, Angela; Dolgounitcheva, Olga; Zakrzewski, V G; Bowen, Kit H; Ortiz, J V

    2013-02-14

    We report the photoelectron spectrum of the 6-azauracil anion. The spectrum is dominated by a broad band exhibiting a maximum at an electron binding energy (EBE) of 1.2 eV. This spectral pattern is indicative of a valence anion. Our calculations were carried out using ab initio electron propagator and other many-body methods. Comparison of the anion and corresponding neutral of 6-azauracil with those of uracil shows that substituting a nitrogen atom for C-H at the C6 position of uracil gives rise to significant changes in the electronic structure of 6-azauracil versus that of uracil. The adiabatic electron affinity (AEA) of the canonical 6-azauracil tautomer is substantially larger than that of canonical uracil. Among the five tautomeric, 6-azauracil anions studied computationally, the canonical structure was found to be the most stable. The vertical detachment energies (VDE) of the canonical, valence-bound anion of 6-azauracil and its closest "very-rare" tautomer have been calculated. Electron propagator calculations on the canonical anion yield a VDE value that is in close agreement with the experimentally determined VDE value of 1.2 eV. The AEA value of 6-azauracil, assessed at the CCSD(T) level of theory to be 0.5 eV, corresponds with the EBE value of the onset of the experimental spectrum.

  20. Development of spin polarized electron beam

    International Nuclear Information System (INIS)

    Nakanishi, Tsutomu

    2001-01-01

    Physical structure of the polarized electron beam production is explained in this paper. Nagoya University group has been improving the quality of beam. The present state of quality and the development objects are described. The new results of the polarized electron reported in 'RES-2000 Workshop' in October 2000, are introduced. The established ground of GaAs type polarized electron beam source, observation of the negative electron affinity (NEA) surface, some problems of NEA surface of high energy polarized electron beam such as the life, time response, the surface charge limited phenomena of NEA surface are explained. The interested reports in the RES-2000 Workshop consisted of observation by SPLEEM (Spin Low Energy Electron Microscope), Spin-STM and Spin-resolved Photoelectron Spectroscopy. To increase the performance of the polarized electron source, we will develop low emittance and large current. (S.Y.)

  1. Borehole radar diffraction tomography

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seong Jun; Kim, Jung Ho; Yi, Myeong Jong; Chung, Seung Hwan; Lee, Hee Il [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1997-12-01

    Tomography is widely used as imaging method for determining subsurface structure. Among the reconstruction algorithms for tomographic imaging, travel time tomography is almost applied to imaging subsurface. But isolated small body comparable with the wavelength could not be well recognized by travel time tomography. Other tomographic method are need to improve the imaging process. In the study of this year, diffraction tomography was investigated. The theory for diffraction tomography is based on the 1st-order Born approximation. Multisource holography, which is similar to Kirchihoff migration, is compared with diffraction tomography. To improve 1st-order Born diffraction tomography, two kinds of filter designed from multisource holography and 2-D green function, respectively, applied on the reconstructed image. The algorithm was tested for the numerical modeling data of which algorithm consists of the analytic computation of radar signal in transmitter and receiver regions and 2-D FDM scheme for the propagation of electromagnetic waves in media. The air-filled cavity model to show a typical diffraction pattern was applied to diffraction tomography imaging, and the result shows accurate location and area of cavity. But the calculated object function is not well matched the real object function, because the air-filled cavity model is not satisfied week scattered inhomogeneity for 1st born approximation, and the error term is included in estimating source wavelet from received signals. In spite of the object function error, the diffraction tomography assist for interpretation of subsurface as if conducted with travel time tomography. And the fracture model was tested, 1st born diffraction tomographic image is poor because of limited view angle coverage and violation of week scatter assumption, but the filtered image resolve the fracture somewhat better. The tested diffraction tomography image confirms effectiveness of filter for enhancing resolution. (author). 14

  2. Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

    Energy Technology Data Exchange (ETDEWEB)

    Bradforth, Stephen Edmund [Univ. of California, Berkeley, CA (United States)

    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-, 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.

  3. Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

    International Nuclear Information System (INIS)

    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 → 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 + CH 3 0H,F + C 2 H 5 OH,F + OH and F + H 2 . 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( 3 P, 1 D) + HF and F + H 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 2 system, comparisons with three-dimensional quantum calculations are made

  4. Diffraction. Powder, amorphous, liquid

    International Nuclear Information System (INIS)

    Sosnowska, I.M.

    1999-01-01

    Neutron powder diffraction is a unique tool to observe all possible diffraction effects appearing in crystal. High-resolution neutron diffractometers have to be used in this study. Analysis of the magnetic structure of polycrystalline materials requires the use of high-resolution neutron diffraction in the range of large interplanar distances. As distinguished from the double axis diffractometers (DAS), which show high resolution only at small interplanar distances, TOF (time-of-flight) diffractometry offers the best resolution at large interplanar distances. (K.A.)

  5. Non-diffractive waves

    CERN Document Server

    Hernandez-Figueroa, Hugo E; Recami, Erasmo

    2013-01-01

    This continuation and extension of the successful book ""Localized Waves"" by the same editors brings together leading researchers in non-diffractive waves to cover the most important results in their field and as such is the first to present the current state.The well-balanced presentation of theory and experiments guides readers through the background of different types of non-diffractive waves, their generation, propagation, and possible applications. The authors include a historical account of the development of the field, and cover different types of non-diffractive waves, including Airy

  6. Ultra-high vacuum photoelectron linear accelerator

    Science.gov (United States)

    Yu, David U.L.; Luo, Yan

    2013-07-16

    An rf linear accelerator for producing an electron beam. The outer wall of the rf cavity of said linear accelerator being perforated to allow gas inside said rf cavity to flow to a pressure chamber surrounding said rf cavity and having means of ultra high vacuum pumping of the cathode of said rf linear accelerator. Said rf linear accelerator is used to accelerate polarized or unpolarized electrons produced by a photocathode, or to accelerate thermally heated electrons produced by a thermionic cathode, or to accelerate rf heated field emission electrons produced by a field emission cathode.

  7. Negative-Ion source for mass selective photodetachment photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Kaesmaier, R.; Baemann, C.; Drechsler, G.; Boesl, U.

    1995-01-01

    We have designed and constructed a negative ion source for mass spectrometry and mass selective photodetachement photoelectron spectroscopy. The characteristics of the source are high anion densities and a large variety of accessible systems. Thus, mass spectra and photoelectron spectra of large unvolatile moelcules (biomolecules), of metal-organic compounds and of molecule water clusters, especially mentioned in this article, have been measured. Combining mass spectrometry, photoelectron spectroscopy (PES) and high resolution ZEKE (zero kinetic energy)-PES (1) should make the apparatus to an ideal diagnostic tool for structural assignment

  8. High energy diffraction

    International Nuclear Information System (INIS)

    Berger, C.

    1995-11-01

    Recent experiments on total hadronic cross sections are reviewed together with results on photo- and electroproduction of vector mesons. New data on diffractive deep inelastic scattering shed light on the nature of the pomeron. (orig.)

  9. Diffraction at TOTEM

    CERN Document Server

    Antchev, G.; Avati, V.; Bagliesi, M.G.; Berardi, V.; Berretti, M.; Bottigli, U.; Bozzo, M.; Brucken, E.; Buzzo, A.; Cafagna, F.; Calicchio, M.; Catanesi, M.G.; Catastini, P.L.; Cecchi, R.; Ciocci, M.A.; Deile, M.; Dimovasili, E.; Eggert, K.; Eremin, V.; Ferro, F.; Garcia, F.; Giani, S.; Greco, V.; Heino, J.; Hilden, T.; Kaspar, J.; Kopal, J.; Kundrat, V.; Kurvinen, K.; Lami, S.; Latino, G.; Lauhakangas, R.; Lippmaa, E.; Lokajicek, M.; Lo Vetere, M.; Lucas Rodriguez, F.; Macri, M.; Magazzu, G.; Meucci, M.; Minutoli, S.; Niewiadomski, H.; Noschis, E.; Notarnicola, G.; Oliveri, E.; Oljemark, F.; Orava, R.; Oriunno, M.; Osterberg, K.; Palazzi, P.; Pedreschi, E.; Petajajarvi, J.; Quinto, M.; Radermacher, E.; Radicioni, E.; Ravotti, F.; Rella, G.; Robutti, E.; Ropelewski, L.; Ruggiero, G.; Rummel, A.; Saarikko, H.; Sanguinetti, G.; Santroni, A.; Scribano, A.; Sette, G.; Snoeys, W.; Spinella, F.; Squillacioti, P.; Ster, A.; Taylor, C.; Trummal, A.; Turini, N.; Whitmore, J.; Wu, J.

    2009-01-01

    The TOTEM experiment at the LHC measures the total proton-proton cross section with the luminosity-independent method and the elastic proton-proton cross-section over a wide |t|-range. It also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage of the large common rapidity coverage for charged and neutral particle detection and the large variety of trigger possibilities even at large luminosities. TOTEM will take data under all LHC beam conditions including standard high luminosity runs to maximize its physics reach. This contribution describes the main features of the TOTEM physics programme including measurements to be made in the early LHC runs. In addition, a novel scheme to extend the diffractive proton acceptance for high luminosity runs by installing proton detectors at IP3 is described.

  10. Diffraction at TOTEM

    CERN Document Server

    Giani, S; Antchev, G; Aspell, P; Avati, V; Bagliesi, M G; Berardi, V; Berretti, M; Besta, M; Bozzo, M; Brücken, E; Buzzo, A; Cafagna, F; Calicchio, M; Catanesi, M G; Cecchi, R; Ciocci, M A; Dadel, P; Deile, M; Dimovasili, E; Eggert, K; Eremin, V; Ferro, F; Fiergolski, A; García, F; Greco, V; Grzanka, L; Heino, J; Hildén, T; Kaspar, J; Kopal, J; Kundrát, V; Kurvinen, K; Lami, S; Latino, G; Lauhakangas, R; Leszko, R; Lippmaa, E; Lokajícek, M; Lo Vetere, M; Lucas Rodriguez, F; Macrí, M; Magazzù, G; Meucci, M; Minutoli, S; Notarnicola, G; Oliveri, E; Oljemark, F; Orava, R; Oriunno, M; Österberg, K; Pedreschi, E; Petäjäjärvi, J; Prochazka, J; Quinto, M; Radermacher, E; Radicioni, E; Ravotti, F; Rella, G; Robutti, E; Ropelewski, L; Rostkowski, M; Ruggiero, G; Rummel, A; Saarikko, H; Sanguinetti, G; Santroni, A; Scribano, A; Sette, G; Snoeys, W; Spinella, F; Ster, A; Taylor, C; Trummal, A; Turini, N; Whitmore, J; Wu, J; Zalewski, M

    2010-01-01

    The primary objective of the TOTEM experiment at the LHC is the measurement of the total proton-proton cross section with the luminosity-independent method and the study of elastic proton-proton cross-section over a wide |t|-range. In addition TOTEM also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage of the large common rapidity coverage for charged and neutral particle detection and the large variety of trigger possibilities even at large luminosities. TOTEM will take data under all LHC beam conditions including standard high luminosity runs to maximise its physics reach. This contribution describes the main features of the TOTEM diffractive physics programme including measurements to be made in the early LHC runs.

  11. Duality in diffraction dissociations

    International Nuclear Information System (INIS)

    Santoro, Alberto.

    1977-01-01

    Diffractive dissociations (aN→a*πN) are naturally explained and a model that accounts for the three-variable correlation (mass-transfer-Jackson angle correlation) is presented. This model takes into account the three possible exchanges: t (pion), u(a*) and s(a) channel exchanger. The physical consequences of the model are: a strong mass-slope correlation due to the zeros of the amplitude, a factorization of diffractive dissociations (factorization of the Pomeron), the possibility of extending this model to double diffractive dissociation and diffraction by nuclei. This model was applied to the NN→NπN reaction. Using the usual parameters of the Deck model, a comparison is made with experiments for all available distributions. the strong slope of the peak at 1400 MeV is naturally explained [fr

  12. DIFFRACTION SYNCHRONIZATION OF LASERS,

    Science.gov (United States)

    semiconductor lasers while suppressing parasitic generation in the plane of the mirror. The diffraction coupling coefficient of open resonators is calculated, and the stability conditions of the synchronized system is determined.

  13. Increased photoelectron transmission in High-pressure photoelectron spectrometers using “swift acceleration”

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, Mårten O.M.; Karlsson, Patrik G. [VG Scienta AB, Box 15120, 750 15 Uppsala (Sweden); Eriksson, Susanna K. [Department of Chemistry-Ångström, Uppsala University, Box 523, 751 20 Uppsala (Sweden); Hahlin, Maria; Siegbahn, Hans; Rensmo, Håkan [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden); Kahk, Juhan M.; Villar-Garcia, Ignacio J.; Payne, David J. [Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Åhlund, John, E-mail: john.ahlund@vgscienta.com [VG Scienta AB, Box 15120, 750 15 Uppsala (Sweden)

    2015-06-11

    A new operation mode of a HPXPS (high-pressure X-ray photoelectron spectroscopy) analyzer is evaluated on a HPXPS system fitted with an Al Kα X-ray source. A variety of metal foil samples (gold, silver and copper) were measured in different sample gas environments (N{sub 2} and H{sub 2}O), and a front aperture diameter of 0.8 mm. The new design concept is based upon “swiftly” accelerating the photoelectrons to kinetic energies of several keV after they pass the analyzer front aperture. Compared to the standard mode, in which the front section between the two first apertures is field-free, this gives a wider angular collection and a lower tendency for electron losses in collisions with gas molecules within the analyzer. With the swift-acceleration mode we attain, depending on the experimental conditions, up to about 3 times higher peak intensities in vacuum and about 10 to 20 times higher peak intensities in the 6–9 mbar regime, depending on kinetic energy. These experimental findings agree well with simulated transmission functions for the analyzer. The new mode of operation enables faster data acquisition than the standard mode of operation, particularly valuable in a home laboratory environment. Further demonstrations of performance are highlighted by measurements of the valence band structure in dye-sensitized solar cell photoelectrodes under a 2 mbar H{sub 2}O atmosphere, a molecularly modified surface of interest in photoelectrochemical devices.

  14. X-ray diffraction 2 - diffraction principles

    International Nuclear Information System (INIS)

    O'Connor, B.

    1999-01-01

    Full text: The computation of powder diffraction intensities is based on the principle that the powder pattern comprises the summation of the intensity contributions from each of the crystallites (or single crystals) in the material. Therefore, it is of value for powder diffractionists to appreciate the form of the expression for calculating single crystal diffraction pattern intensities. This knowledge is especially important for Rietveld analysis practitioners in terms of the (i) mathematics of the method and (ii) retrieving single crystal structure data from the literature. We consider the integrated intensity from a small single crystal being rotated at velocity ω through the Bragg angle θ for reflection (hkl).... I(hkl) = [l o /ω]. [e 4 /m 2 c 4 ]. [λ 3 δV F(hkl) 2 /υ 2 ].[(1+cos 2 2θ)/2sin2θ] where e, m and c are the usual fundamental constants; λ is the x-ray wavelength, δV is the crystallite volume; F(hkl) is the structure factor; υ is the unit cell volume; and (1+cos 2 θ)/2sin2θ] is the Lorentz-polarisation factor for an unpolarised incident beam. The expression does not include a contribution for extinction. The influence of factors λ, δV, F(hkl) and υ on the intensities should be appreciated by powder diffractionists, especially the structure factor, F(hkl), which is responsible for the fingerprint nature of diffraction patterns, such as the rise and fall of intensity from peak to peak. The structure factor expression represents the summation of the scattered waves from each of the j scattering centres (i e atoms) in the unit cell: F(hkl) Σ f j exp[2πi (h.x j +k.y i +l. z i )] T j . Symbol f is the scattering factor (representing the atom-type scattering efficiency); (x, y, z) are the fractional position coordinates of atom j within the unit cell; and T is the thermal vibration factor for the atom given by: T j = 8π 2 2 > sin 2 θ/λ 2 with 2 > being the mean-square vibration amplitude of the atom (assumed to be isotropic). The

  15. Polarization developments

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist

  16. Polarized Light Microscopy

    Science.gov (United States)

    Frandsen, Athela F.

    2016-01-01

    Polarized light microscopy (PLM) is a technique which employs the use of polarizing filters to obtain substantial optical property information about the material which is being observed. This information can be combined with other microscopy techniques to confirm or elucidate the identity of an unknown material, determine whether a particular contaminant is present (as with asbestos analysis), or to provide important information that can be used to refine a manufacturing or chemical process. PLM was the major microscopy technique in use for identification of materials for nearly a century since its introduction in 1834 by William Fox Talbot, as other techniques such as SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy), XPD (X-ray Powder Diffraction), and TEM (Transmission Electron Microscopy) had not yet been developed. Today, it is still the only technique approved by the Environmental Protection Agency (EPA) for asbestos analysis, and is often the technique first applied for identification of unknown materials. PLM uses different configurations in order to determine different material properties. With each configuration additional clues can be gathered, leading to a conclusion of material identity. With no polarizing filter, the microscope can be used just as a stereo optical microscope, and view qualities such as morphology, size, and number of phases. With a single polarizing filter (single polars), additional properties can be established, such as pleochroism, individual refractive indices, and dispersion staining. With two polarizing filters (crossed polars), even more can be deduced: isotropy vs. anisotropy, extinction angle, birefringence/degree of birefringence, sign of elongation, and anomalous polarization colors, among others. With the use of PLM many of these properties can be determined in a matter of seconds, even for those who are not highly trained. McCrone, a leader in the field of polarized light microscopy, often

  17. Photoelectron angular distributions for states of any mixed character: An experiment-friendly model for atomic, molecular, and cluster anions

    International Nuclear Information System (INIS)

    Khuseynov, Dmitry; Blackstone, Christopher C.; Culberson, Lori M.; Sanov, Andrei

    2014-01-01

    We present a model for laboratory-frame photoelectron angular distributions in direct photodetachment from (in principle) any molecular orbital using linearly polarized light. A transparent mathematical approach is used to generalize the Cooper-Zare central-potential model to anionic states of any mixed character. In the limit of atomic-anion photodetachment, the model reproduces the Cooper-Zare formula. In the case of an initial orbital described as a superposition of s and p-type functions, the model yields the previously obtained s-p mixing formula. The formalism is further advanced using the Hanstorp approximation, whereas the relative scaling of the partial-wave cross-sections is assumed to follow the Wigner threshold law. The resulting model describes the energy dependence of photoelectron anisotropy for any atomic, molecular, or cluster anions, usually without requiring a direct calculation of the transition dipole matrix elements. As a benchmark case, we apply the p-d variant of the model to the experimental results for NO − photodetachment and show that the observed anisotropy trend is described well using physically meaningful values of the model parameters. Overall, the presented formalism delivers insight into the photodetachment process and affords a new quantitative strategy for analyzing the photoelectron angular distributions and characterizing mixed-character molecular orbitals using photoelectron imaging spectroscopy of negative ions

  18. Photoelectron angular distributions for states of any mixed character: An experiment-friendly model for atomic, molecular, and cluster anions

    Science.gov (United States)

    Khuseynov, Dmitry; Blackstone, Christopher C.; Culberson, Lori M.; Sanov, Andrei

    2014-09-01

    We present a model for laboratory-frame photoelectron angular distributions in direct photodetachment from (in principle) any molecular orbital using linearly polarized light. A transparent mathematical approach is used to generalize the Cooper-Zare central-potential model to anionic states of any mixed character. In the limit of atomic-anion photodetachment, the model reproduces the Cooper-Zare formula. In the case of an initial orbital described as a superposition of s and p-type functions, the model yields the previously obtained s-p mixing formula. The formalism is further advanced using the Hanstorp approximation, whereas the relative scaling of the partial-wave cross-sections is assumed to follow the Wigner threshold law. The resulting model describes the energy dependence of photoelectron anisotropy for any atomic, molecular, or cluster anions, usually without requiring a direct calculation of the transition dipole matrix elements. As a benchmark case, we apply the p-d variant of the model to the experimental results for NO- photodetachment and show that the observed anisotropy trend is described well using physically meaningful values of the model parameters. Overall, the presented formalism delivers insight into the photodetachment process and affords a new quantitative strategy for analyzing the photoelectron angular distributions and characterizing mixed-character molecular orbitals using photoelectron imaging spectroscopy of negative ions.

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

    International Nuclear Information System (INIS)

    Lynch, D.W.

    2004-01-01

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

  20. Valence photoelectron spectrum of KBr: Effects of electron correlation

    International Nuclear Information System (INIS)

    Calo, A.; Huttula, M.; Patanen, M.; Aksela, H.; Aksela, S.

    2008-01-01

    The valence photoelectron spectrum has been measured for molecular KBr. Experimental energies of the main and satellite structures have been compared with the results of ab initio calculations based on molecular orbital theory including configuration and multiconfiguration interaction approaches. Comparison between the experimental KBr spectrum and previously reported Kr valence photoelectron spectrum has also been performed in order to find out if electron correlation is of the same importance in the valence ionized state of KBr as in the corresponding state of Kr

  1. Photoelectron Imaging Spectroscopy as a Window to Unexpected Molecules

    Science.gov (United States)

    Blackstone, Christopher C.

    2017-06-01

    Targeting an anion with the formula CH_{3}O_{3} for exploration with photoelectron imaging spectroscopy, we determine its identity to be dihydroxymethanolate, an anion largely absent in the literature, and the conjugate base of the hypothetical species orthoformic acid. Comparing the observed photoelectron spectrum to CCSD-EOM-IP and CCSD-EOM-SF calculations completed in QChem and Franck-Condon overlap simulations in PESCAL, we are able to determine with confidence the connectivity of the atoms in this molecule.

  2. Neutron polarization

    International Nuclear Information System (INIS)

    Firk, F.W.K.

    1976-01-01

    Some recent experiments involving polarized neutrons are discussed; they demonstrate how polarization studies provide information on fundamental aspects of nuclear structure that cannot be obtained from more traditional neutron studies. Until recently, neutron polarization studies tended to be limited either to very low energies or to restricted regions at higher energies, determined by the kinematics of favorable (p, vector n) and (d, vector n) reactions. With the advent of high intensity pulsed electron and proton accelerators and of beams of vector polarized deuterons, this is no longer the case. One has entered an era in which neutron polarization experiments are now being carried out, in a routine way, throughout the entire range from thermal energies to tens-of-MeV. The significance of neutron polarization studies is illustrated in discussions of a wide variety of experiments that include the measurement of T-invariance in the β-decay of polarized neutrons, a search for the effects of meson exchange currents in the photo-disintegration of the deuteron, the determination of quantum numbers of states in the fission of aligned 235 U and 237 Np induced by polarized neutrons, and the double- and triple-scattering of fast neutrons by light nuclei

  3. Beam steering for virtual/augmented reality displays with a cycloidal diffractive waveplate.

    Science.gov (United States)

    Chen, Haiwei; Weng, Yishi; Xu, Daming; Tabiryan, Nelson V; Wu, Shin-Tson

    2016-04-04

    We proposed a switchable beam steering device with cycloidal diffractive waveplate (CDW) for eye tracking in a virtual reality (VR) or augmented reality (AR) display system. Such a CDW diffracts the incident circularly polarized light to the first order with over 95% efficiency. To convert the input linearly polarized light to right-handed or left-handed circular polarization, we developed a broadband polarization switch consisting of a twisted nematic liquid crystal cell and an achromatic quarter-wave retardation film. By cascading 2-3 CDWs together, multiple diffraction angles can be achieved. To suppress the color dispersion, we proposed two approaches to obtain the same diffraction angle for red, green, and blue LEDs-based full color displays. Our device exhibits several advantages, such as high diffraction efficiency, fast response time, low power consumption, and low cost. It holds promise for the emerging VR/AR displays.

  4. Polarization holography

    DEFF Research Database (Denmark)

    Nikolova, L.; Ramanujam, P.S.

    Current research into holography is concerned with applications in optically storing, retrieving, and processing information. Polarization holography has many unique properties compared to conventional holography. It gives results in high efficiency, achromaticity, and special polarization...... properties. This books reviews the research carried out in this field over the last 15 years. The authors provide basic concepts in polarization and the propagation of light through anisotropic materials, before presenting a sound theoretical basis for polarization holography. The fabrication...... and characterization of azobenzene based materials, which remain the most efficient for the purpose, is described in detail. This is followed by a description of other materials that are used in polarization holography. An in-depth description of various applications, including display holography and optical storage...

  5. Quark-antiquark production in DIS diffractive dissociation

    International Nuclear Information System (INIS)

    Bartels, J.; Lotter, H.; Wuesthoff, M.

    1996-02-01

    We calculate the cross section for the production of two jets with large transverse momenta k 2 in DIS diffractive dissociation for both transverse and longitudinally polarized photons. The scale which defines the hardness of the Pomeron is found to be k 2 (Q 2 +M 2 )/M 2 . We present analytic expressions and discuss numerical results relevant for the diffractive dissociation at HERA. (orig.)

  6. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources.

    Science.gov (United States)

    Pincelli, T; Petrov, V N; Brajnik, G; Ciprian, R; Lollobrigida, V; Torelli, P; Krizmancic, D; Salvador, F; De Luisa, A; Sergo, R; Gubertini, A; Cautero, G; Carrato, S; Rossi, G; Panaccione, G

    2016-03-01

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  7. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

    International Nuclear Information System (INIS)

    Pincelli, T.; Rossi, G.; Petrov, V. N.; Brajnik, G.; Carrato, S.; Ciprian, R.; Torelli, P.; Krizmancic, D.; Salvador, F.; De Luisa, A.; Panaccione, G.; Lollobrigida, V.; Sergo, R.; Gubertini, A.; Cautero, G.

    2016-01-01

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  8. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

    Science.gov (United States)

    Pincelli, T.; Petrov, V. N.; Brajnik, G.; Ciprian, R.; Lollobrigida, V.; Torelli, P.; Krizmancic, D.; Salvador, F.; De Luisa, A.; Sergo, R.; Gubertini, A.; Cautero, G.; Carrato, S.; Rossi, G.; Panaccione, G.

    2016-03-01

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  9. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

    Energy Technology Data Exchange (ETDEWEB)

    Pincelli, T., E-mail: pincelli@iom.cnr.it; Rossi, G. [Dipartimento di Fisica, Università degli studi di Milano, Via Celoria 16, 20133 Milano (Italy); Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, 34149 Trieste (Italy); Petrov, V. N. [Saint Petersburg State Polytechnical University, Politechnicheskaya Street 29, 195251 Saint Petersburg (Russian Federation); Brajnik, G.; Carrato, S. [Università degli Studi di Trieste, Piazzale Europa 1, 34127 Trieste (Italy); Ciprian, R.; Torelli, P.; Krizmancic, D.; Salvador, F.; De Luisa, A.; Panaccione, G. [Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, 34149 Trieste (Italy); Lollobrigida, V. [Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Sergo, R.; Gubertini, A.; Cautero, G. [Sincrotrone Trieste S.C.p.A, Strada Statale 14-km 163.5 in AREA Science Park, Basovizza, 34149 Trieste (Italy)

    2016-03-15

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  10. Diffraction. Single crystal, magnetic

    International Nuclear Information System (INIS)

    Heger, G.

    1999-01-01

    The analysis of crystal structure and magnetic ordering is usually based on diffraction phenomena caused by the interaction of matter with X-rays, neutrons, or electrons. Complementary information is achieved due to the different character of X-rays, neutrons and electrons, and hence their different interactions with matter and further practical aspects. X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (K.A.)

  11. Effect of triethanolamine and heliotropin on cathodic polarization of weakly acidic baths and properties of Sn-Ag-Cu alloy electrodeposits

    International Nuclear Information System (INIS)

    Zhang Jinqiu; An Maozhong; Chang Limin; Liu Guiyuan

    2008-01-01

    The effect of triethanolamine (TEA) and heliotropin (HT) on the cathodic polarization of weakly acidic baths and the properties of Sn-Ag-Cu alloy electrodeposits were investigated. Lead-free Sn-Ag-Cu solder alloy were electrodeposited in weakly acidic baths (pH 5.5) containing Sn(CH 3 SO 3 ) 2 , AgI, Cu(CH 3 SO 3 ) 2 , K 4 P 2 O 7 , KI, hydroquinone, TEA, HT and methylsulfonic acid (MSA). The cathodic polarization of baths and the properties of electrodeposits were evaluated by Liner sweep voltammetry (LSV), scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results indicate that HT is a main brightening agent that increases the cathodic polarization of baths and refines the grains of electrodeposits; TEA is a complexing agent for copper ions and a brightening promoter that decreases the cathodic polarization of baths and densifies the electrodeposits. The bright, compact, and smooth Sn-Ag-Cu alloy electrodeposits contain 88-95 wt% tin, 5-10 wt% silver and 0.5-2 wt% copper. Organic compounds used in the baths neither adsorb on the electrodeposits surfaces nor are included in the electrodeposits. It can be therefore concluded that the use of both TEA and HT is better than that of them either in the process of electroplating bright Sn-Ag-Cu alloy

  12. Diffraction in nuclear scattering

    International Nuclear Information System (INIS)

    Wojciechowski, H.

    1986-01-01

    The elastic scattering amplitudes for charged and neutral particles have been decomposed into diffractive and refractive parts by splitting the nuclear elastic scattering matrix elements into components responsible for these effects. It has been shown that the pure geometrical diffractive effect which carries no information about the nuclear interaction is always predominant at forward angle of elastic angular distributions. This fact suggests that for strongly absorbed particles only elastic cross section at backward angles, i.e. the refractive cross section, can give us basic information about the central nuclear potential. 12 refs., 4 figs., 1 tab. (author)

  13. Dynamics from diffraction

    International Nuclear Information System (INIS)

    Goodwin, Andrew L.; Tucker, Matthew G.; Cope, Elizabeth R.; Dove, Martin T.; Keen, David A.

    2006-01-01

    We explore the possibility that detailed dynamical information might be extracted from powder diffraction data. Our focus is a recently reported technique that employs statistical analysis of atomistic configurations to calculate dynamical properties from neutron total scattering data. We show that it is possible to access the phonon dispersion of low-frequency modes using such an approach, without constraining the results in terms of some pre-defined dynamical model. The high-frequency regions of the phonon spectrum are found to be less well preserved in the diffraction data

  14. Versatile spin-polarized electron source

    Science.gov (United States)

    Jozwiak, Chris; Park, Cheol -Hwan; Gotlieb, Kenneth; Louie, Steven G.; Hussain, Zahid; Lanzara, Alessandra

    2015-09-22

    One or more embodiments relate generally to the field of photoelectron spin and, more specifically, to a method and system for creating a controllable spin-polarized electron source. One preferred embodiment of the invention generally comprises: method for creating a controllable spin-polarized electron source comprising the following steps: providing one or more materials, the one or more materials having at least one surface and a material layer adjacent to said surface, wherein said surface comprises highly spin-polarized surface electrons, wherein the direction and spin of the surface electrons are locked together; providing at least one incident light capable of stimulating photoemission of said surface electrons; wherein the photon polarization of said incident light is tunable; and inducing photoemission of the surface electron states.

  15. Synthesis, structural, X-ray photoelectron spectroscopy (XPS) studies and IR induced anisotropy of Tl{sub 4}HgI{sub 6} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Parasyuk, O.V. [Department of Inorganic and Physical Chemistry, Lesya Ukrainka Eastern European National University, Voli Ave. 13, Lutsk, 43025 (Ukraine); Khyzhun, O.Y. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky St., 03142, Kyiv (Ukraine); Piasecki, M. [Institute of Physics, J. Dlugosz University Częstochowa, Armii Krajowej 13/15, Częstochowa (Poland); Kityk, I.V., E-mail: iwank74@gmail.com [Electrical Engineering Department, Czestochowa University Technology, Armii Krajowej 17, PL-42-217, Czestochowa (Poland); Lakshminarayana, G. [Wireless and Photonic Networks Research Centre, Faculty of Engineering, Universiti Putra Malaysia, 43400, Serdang, Selangor (Malaysia); Luzhnyi, I. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky St., 03142, Kyiv (Ukraine); Fochuk, P.M. [Yuriy Fed’kovych Chernivtsi National University, 2 Kotziubynskoho Str., 58012, Chernivtsi (Ukraine); Fedorchuk, A.O. [Department of Inorganic and Organic Chemistry, Lviv National University of Veterinary Medicine and Biotechnologies, Pekarska Street 50, 79010, Lviv (Ukraine); Levkovets, S.I.; Yurchenko, O.M.; Piskach, L.V. [Department of Inorganic and Physical Chemistry, Lesya Ukrainka Eastern European National University, Voli Ave. 13, Lutsk, 43025 (Ukraine)

    2017-02-01

    In the present work, we report on the synthesis and structural properties including X-ray protoelectron spectroscopy (XPS) analysis of Tl{sub 4}HgI{sub 6} crystals that were grown by Bridgman-Stockbarger method up to 80 mm in length and 18 mm in diameter. The existence of the ternary compound Tl{sub 4}HgI{sub 6} that melts incongruently at 641 K was confirmed. Phase equilibria and structural properties for the TlI–HgI{sub 2} system were investigated by differential thermal analysis (DTA) and X-ray diffraction (XRD) methods. X-ray photoelectron spectra were measured for both pristine and Ar{sup +} ion-bombarded Tl{sub 4}HgI{sub 6} single crystal surfaces. The data reveal that the Tl{sub 4}HgI{sub 6} single crystal is sensitive with respect to Ar{sup +} ion-bombardment as 3.0 keV Ar{sup +} irradiation over 5 min at an ion current density 14 μA/cm{sup 2} induces changes to the elemental stoichiometry of the Tl{sub 4}HgI{sub 6} surface, leading to a decrease of the mercury content in the topmost surface layers. X-ray photoelectron spectroscopy (XPS) measurements indicate very low hygroscopic nature of the Tl{sub 4}HgI{sub 6} single crystal surface. The IR coherent bicolor laser treatment at wavelengths 10.6/5.3 μm has shown an occurrence of anisotropy at wavelengths 1540 nm of Er:glass laser. This may open the applications of Tl{sub 4}HgI{sub 6} as a material for IR laser triggering. - Highlights: • Phase diagram of the HgI{sub 2}–TlI system was built. • Tl{sub 4}HgI{sub 6} single crystals were grown by Bridgman Stockbarger method. • XRD, XPS analysis was done. • Ir induced anisotropy was established. • The compounds may be proposed as Ir laser operated polarizers.

  16. Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

    Science.gov (United States)

    Rafiee Fanood, Mohammad M.; Janssen, Maurice H. M.; Powis, Ivan

    2016-09-01

    Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy.

  17. CLASSIFICATION FOR ANGLE-DEPENDENT POLARIZED PHOTOEMISSION SPECTRA USING MAGNETIC-MOMENTS ANALYSIS

    NARCIS (Netherlands)

    VANDERLAAN, G; THOLE, BT

    The angular distribution of photoelectrons from a core level or localized valence level excited with circularly or linearly polarized Xrays is shown to contain the complete one-electron information of the ground state of a magnetic polarized atom. We generalize the definition of the fundamental

  18. An X-ray photoelectron spectroscopic study of the B-N-Ti system

    Energy Technology Data Exchange (ETDEWEB)

    Seal, S. [Lawrence Berkeley National Lab., CA (United States); Barr, T.L. [Univ. of Wisconsin, Milwaukee, WI (United States); Sobczak, N. [Foundry Research Inst., Cracow (Poland); Benko, E. [Inst. of Metal Cutting, Cracow (Poland); Morgiel, J. [Polish Academy of Sciences, Cracow (Poland). Inst. of Metallurgy and Materials Science

    1997-03-01

    Composite nitrides (such as BN, TiN) are widely used in various industrial applications because of their extreme wear and corrosion resistance, thermal and electrical properties. In order to obtain composite materials with these optimal properties, it is important to elucidate whether any chemical reactions occur at nitride/metal interfaces, e.g., those involving BN-Ti/TiN. Materials of interest include the deposition by PVD of Ti and TiN on BN substrates. Some of these systems were then subjected to varying degrees of physical and thermal alteration. Detailed X-ray photoelectron spectroscopy (XPS) has therefore been rendered of these interfaces using cross-sectional display and sputter etching. Resulting structural and morphological features have been investigated with transmission electron microscopy (TEM) and X-ray diffraction (XRD). Diffusion of the nitridation, oxynitride formation and interfacial growth are of general interest.

  19. Ionization, photoelectron dynamics and elastic scattering in relativistic, ultra-strong field

    Science.gov (United States)

    Luo, Sui

    Ultrastrong laser-matter interaction has direct bearing to next generation technologies including plasma acceleration, laser fusion and attosecond X-ray generation. The commonly known physics in strong field becomes different as one progress to ultrastrong field. The works presented in this dissertation theoretically study the influence of relativistic effect and magnetic component of the laser field on the ionization, photoelectron dynamics and elastic scattering processes. The influence of magnetic component (B laser) of circularly polarized (CP) ultrastrong fields (up to3 x 1022 W/cm2) on atomic bound state dynamics is investigated. The Poincare plots are used to find the changes in trajectory energies are on the order of a few percent for intensities up to1 x 1022 W/cm2. It is found that at intensities where ionization approaches 50% for the bound state, the small changes from Blaser of the circular polarized light can actually result in a several-fold decrease in ionization probability. The force on the bound electron exerted by the Lorentz force from B laser is perpendicular to the rotating plane of the circular polarized light, and this nature makes those trajectories which are aligned away from the minimum in the potential barrier stabilized against tunneling ionization. Our results provide a classical understanding for ionization in ultrastrong fields and indicate that relativistic effects in ultrastrong field ionization may most easily be seen with CP fields. The photoelectron energy spectra from elastic rescattering in ultrastrong laser fields (up to 2x1019 W/cm2) is studied by using a relativistic adaption of a semi-classical three-step recollision model. The Hartree-Fock scattering potentials are used in calculating the elastic rescattering for both hydrogenlike and noble gas species. It is found that there is a reduction in elastic rescattering for intensities beyond 6 x 1016 W/cm2 when the laser Lorentz deflection of the photoelectron exceeds its

  20. Diffraction at collider energies

    International Nuclear Information System (INIS)

    Frankfurt, L.L.

    1992-01-01

    Lessons with ''soft'' hadron physics to explain (a) feasibility to observe and to investigate color transparency, color opacity effects at colliders; (b) significant probability and specific features of hard diffractive processes; (c) feasibility to investigate components of parton wave functions of hadrons with minimal number of constituents. This new physics would be more important with increase of collision energy

  1. Diffraction through partial identity

    International Nuclear Information System (INIS)

    Blum, W.

    1981-06-01

    A model of diffraction dissociation is proposed in which the quantum-mechanical interference between the incoming and the outgoing wave determines the cross-section. This interference occurs due to the finite life-time of the excited state. (orig.)

  2. Diffractive optics for industrial and commercial applications

    Energy Technology Data Exchange (ETDEWEB)

    Turunen, J. [Joensuu Univ. (Finland); Wyrowski, F. [eds.] [Jena Univ. (Germany)

    1997-12-31

    The following topics were dealt with: diffractive optics, diffraction gratings, optical system design with diffractive optics, continuous-relief diffractive lenses and microlens arrays, diffractive bifocal intraocular lenses, diffractive laser resonators, diffractive optics for semiconductor lasers, diffractive elements for optical image processing, photorefractive crystals in optical measurement systems, subwavelenth-structured elements, security applications, diffractive optics for solar cells, holographic microlithography. 999 refs.

  3. Ionic polarization

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1992-01-01

    Ferroelectricity occurs in many different kinds of materials. Many of the technologically important solids, which are ferroelectric, can be classified as ionic. Any microscopic theory of ferroelectricity must contain a description of local polarization forces. We have collaborated in the development of a theory of ionic polarization which is quite successful. Its basic assumption is that the polarization is derived from the properties of the individual ions. We have applied this theory successfully to diverse subjects as linear and nonlinear optical response, phonon dispersion, and piezoelectricity. We have developed numerical methods using the local Density approximation to calculate the multipole polarizabilities of ions when subject to various fields. We have also developed methods of calculating the nonlinear hyperpolarizability, and showed that it can be used to explain light scattering experiments. This paper elaborates on this polarization theory

  4. Tracking ultrafast relaxation dynamics of furan by femtosecond photoelectron imaging

    International Nuclear Information System (INIS)

    Liu, Yuzhu; Knopp, Gregor; Qin, Chaochao; Gerber, Thomas

    2015-01-01

    Graphical abstract: - Highlights: • Relaxation dynamics of furan are tracked by femtosecond photoelectron imaging. • The mechanism for ultrafast formation of α-carbene and β-carbene is proposed. • Ultrafast internal conversion from S 2 to S 1 is observed. • The transient characteristics of the fragment ions are obtained. • Single-color multi-photon ionization dynamics at 800 nm are also studied. - Abstract: Ultrafast internal conversion dynamics of furan has been studied by femtosecond photoelectron imaging (PEI) coupled with photofragmentation (PF) spectroscopy. Photoelectron imaging of single-color multi-photon ionization and two-color pump–probe ionization are obtained and analyzed. Photoelectron bands are assigned to the related states. The time evolution of the photoelectron signal by pump–probe ionization can be well described by a biexponential decay: two rapid relaxation pathways with time constants of ∼15 fs and 85 (±11) fs. The rapid relaxation is ascribed to the ultrafast internal conversion (IC) from the S 2 state to the vibrationally hot S 1 state. The second relaxation process is attributed to the redistributions and depopulation of secondarily populated high vibronic S 1 state and the formation of α-carbene and β-carbene by H immigration. Additionally, the transient characteristics of the fragment ions are also measured and discussed as a complementary understanding

  5. Tracking ultrafast relaxation dynamics of furan by femtosecond photoelectron imaging

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yuzhu, E-mail: yuzhu.liu@gmail.com [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Knopp, Gregor [Paul Scherrer Institute, Villigen 5232 (Switzerland); Qin, Chaochao [Department of Physics, Henan Normal University, Xinxiang 453007 (China); Gerber, Thomas [Paul Scherrer Institute, Villigen 5232 (Switzerland)

    2015-01-13

    Graphical abstract: - Highlights: • Relaxation dynamics of furan are tracked by femtosecond photoelectron imaging. • The mechanism for ultrafast formation of α-carbene and β-carbene is proposed. • Ultrafast internal conversion from S{sub 2} to S{sub 1} is observed. • The transient characteristics of the fragment ions are obtained. • Single-color multi-photon ionization dynamics at 800 nm are also studied. - Abstract: Ultrafast internal conversion dynamics of furan has been studied by femtosecond photoelectron imaging (PEI) coupled with photofragmentation (PF) spectroscopy. Photoelectron imaging of single-color multi-photon ionization and two-color pump–probe ionization are obtained and analyzed. Photoelectron bands are assigned to the related states. The time evolution of the photoelectron signal by pump–probe ionization can be well described by a biexponential decay: two rapid relaxation pathways with time constants of ∼15 fs and 85 (±11) fs. The rapid relaxation is ascribed to the ultrafast internal conversion (IC) from the S{sub 2} state to the vibrationally hot S{sub 1} state. The second relaxation process is attributed to the redistributions and depopulation of secondarily populated high vibronic S{sub 1} state and the formation of α-carbene and β-carbene by H immigration. Additionally, the transient characteristics of the fragment ions are also measured and discussed as a complementary understanding.

  6. Photoelectron spectra and electronic structure of some spiroborate complexes

    Energy Technology Data Exchange (ETDEWEB)

    Vovna, V.I.; Tikhonov, S.A.; Lvov, I.B., E-mail: lvov.ib@dvfu.ru; Osmushko, I.S.; Svistunova, I.V.; Shcheka, O.L.

    2014-12-15

    Highlights: • The electronic structure of three spiroborate complexes—boron 1,2-dioxyphenylene β-diketonates has been investigated. • UV and X-ray photoelectron spectra have been interpreted. • DFT calculations have been used for interpretation of spectral bands. • The binding energy of nonequivalent carbon and oxygen atoms were measured. • The structure of X-ray photoelectron spectra of the valence electrons is in good agreement with the energies and composition of Kohn–Sham orbitals. - Abstract: The electronic structure of the valence and core levels of three spiroborate complexes – boron 1,2-dioxyphenylene β-diketonates – has been investigated by methods of UV and X-ray photoelectron spectroscopy and quantum chemical density functional theory. The ionization energy of π- and n-orbitals of the dioxyphenylene fragment and β-diketonate ligand were measured from UV photoelectron spectra. This made it possible to determine the effect of substitution of one or two methyl groups by the phenyl in diketone on the electronic structure of complexes. The binding energy of nonequivalent carbon and oxygen atoms were measured from X-ray photoelectron spectra. The results of calculations of the energy of the valence orbitals of complexes allowed us to refer bands observed in the spectra of the valence electrons to the 2s-type levels of carbon and oxygen.

  7. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    Science.gov (United States)

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.

  8. Optical system storage design with diffractive optical elements

    Science.gov (United States)

    Kostuk, Raymond K.; Haggans, Charles W.

    1993-01-01

    Optical data storage systems are gaining widespread acceptance due to their high areal density and the ability to remove the high capacity hard disk from the system. In magneto-optical read-write systems, a small rotation of the polarization state in the return signal from the MO media is the signal which must be sensed. A typical arrangement used for detecting these signals and correcting for errors in tracking and focusing on the disk is illustrated. The components required to achieve these functions are listed. The assembly and alignment of this complex system has a direct impact on cost, and also affects the size, weight, and corresponding data access rates. As a result, integrating these optical components and improving packaging techniques is an active area of research and development. Most designs of binary optic elements have been concerned with optimizing grating efficiency. However, rigorous coupled wave models for vector field diffraction from grating surfaces can be extended to determine the phase and polarization state of the diffracted field, and the design of polarization components. A typical grating geometry and the phase and polarization angles associated with the incident and diffracted fields are shown. In our current stage of work, we are examining system configurations which cascade several polarization functions on a single substrate. In this design, the beam returning from the MO disk illuminates a cascaded grating element which first couples light into the substrate, then introduces a quarter wave retardation, then a polarization rotation, and finally separates s- and p-polarized fields through a polarization beam splitter. The input coupler and polarization beam splitter are formed in volume gratings, and the two intermediate elements are zero-order elements.

  9. Energetic and Spatial Bonding Properties from Angular Distributions of Ultraviolet Photoelectrons: Application to the GaAs(110) Surface

    International Nuclear Information System (INIS)

    Fadley, C.S.; Fadley, C.S.; Van Hove, M.A.

    1997-01-01

    Angle-resolved ultraviolet photoemission spectra are interpreted by combining the energetics and spatial properties of the contributing states. One-step calculations are in excellent agreement with new azimuthal experimental data for GaAs(110). Strong variations caused by the dispersion of the surface bands permit an accurate mapping of the electronic structure. The delocalization of the valence states is discussed analogous to photoelectron diffraction. The spatial origin of the electrons is determined, and found to be strongly energy dependent, with uv excitation probing the bonding region. copyright 1997 The American Physical Society

  10. Polarization measurement for internal polarized gaseous targets

    International Nuclear Information System (INIS)

    Ye Zhenyu; Ye Yunxiu; Lv Haijiang; Mao Yajun

    2004-01-01

    The authors present an introduction to internal polarized gaseous targets, polarization method, polarization measurement method and procedure. To get the total nuclear polarization of hydrogen atoms (including the polarization of the recombined hydrogen molecules) in the target cell, authors have measured the parameters relating to atomic polarization and polarized hydrogen atoms and molecules. The total polarization of the target during our measurement is P T =0.853 ± 0.036. (authors)

  11. Polarisation resonance in X-ray diffraction

    International Nuclear Information System (INIS)

    Goodman, P.; Paterson, D.; Matheson, S.

    1994-01-01

    The study of crystal structures by means of dynamic X-ray diffraction has placed a challenge to theoreticians to revise the X-ray diffraction theory based on Maxwell's equation. In this paper the feasibility of using 'polarisation resonance' as a tool in the determination of absolute configuration for asymmetric structures is investigated. Two (left- and right-handed), σ + and σ- , circular polarization states for 3-beam conditions are considered. Moreover, extending interaction into the 3 rd. dimension (normal to the beam) opens the possibility of absolute configuration determination of asymmetric structures in 3 dimensions. The computational scheme used is shown in terms of scattering diagrams. 7 refs., 1 tab., 6 figs

  12. Contribution to diffraction theory

    International Nuclear Information System (INIS)

    Chako, N.

    1966-11-01

    In a first part, we have given a general and detailed treatment of the modern theory of diffraction. The rigorous theory is formulated as a boundary value problem of the wave equation or Maxwell equations. However, up to the present time, such a program of treating diffraction by optical systems, even for simple optical instruments, has not been realized due to the complicated character of the boundary conditions. The recent developments show clearly the nature of the approximation of the classical theories originally due to Fresnel and Young, later formulated in a rigorous manner by Kirchhoff and Rubinowicz, respectively and, at the same time the insufficiency of these theories in explaining a number of diffraction phenomena. Furthermore, we have made a study of the limitations of the approximate theories and the recent attempts to improve these. The second part is devoted to a general mathematical treatment of the theory of diffraction of optical systems including aberrations. After a general and specific analysis of geometrical and wave aberrations along classical and modern (Nijboer) lines, we have been able to evaluate the diffraction integrals representing the image field at any point in image space explicitly, when the aberrations are small. Our formulas are the generalisations of all anterior results obtained by previous investigators. Moreover, we have discussed the Zernike-Nijboer theory of aberration and generalised it not only for rotational systems, but also for non-symmetric systems as well, including the case of non circular apertures. The extension to non-circular apertures is done by introducing orthogonal functions or polynomials over such aperture shapes. So far the results are valid for small aberrations, that is to say, where the deformation of the real wave front emerging from the optical system is less than a wave length of light or of the electromagnetic wave from the ideal wave front. If the aberrations are large, then one must employ the

  13. Polarized vacuum ultraviolet and X-radiation

    International Nuclear Information System (INIS)

    Samson, J.A.R.

    1978-01-01

    The most intense source of polarized vacuum UV and X-radiation is synchrotron radiation, which exhibits a degree of partially polarized light between about 80-100%. However, the radiation transmitted by vacuum UV monochromators can also be highly polarized. The Seya-Namioka type of monochromator can produce partially polarized radiation between 50-80%. For certain experiments it is necessary to know the degree of polarisation of the radiation being used. Also, when synchrotron radiation and a monochromator are combined the polarization characteristic of both should be known in order to make full use of these polarization properties. The polarizing effect on monochromators (i.e. diffraction gratings) have been measured at the Seya angle and at grazing angles for various spectral orders. The author presents the first experimental evidence that the reciprocity law holds for polarization by reflection where the angle of incidence and diffraction are unequal. These results are reviewed along with the techniques for measuring the degree of polarization. (Auth.)

  14. Tribocharging in electrostatic beneficiation of coal: Effects of surface composition on work function as measured by x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy in air

    International Nuclear Information System (INIS)

    Trigwell, S.; Mazumder, M.K.; Pellissier, R.

    2001-01-01

    The cleaning of coal by electrostatic beneficiation is based on tribocharging characteristics of pulverized coal particles with diameter smaller than 120 μm. The tribocharging process should be such that the organic coal particles must charge with a polarity opposite to that of the sulfur and the mineral containing particles so that coal can be separated from minerals by using a charge separator. However, the charge distribution of electrostatically separated coal particles indicates that coal exhibits bipolar charging. A significant fraction of the coal particles charges negatively which appears to be in conflict with expectations in that the organic coal particles should charge positively, and the mineral particles, present as impurities such as pyrite, charge negatively when tribocharged against copper. The relative work functions of the particles (coal and mineral) and that of the metal surface (copper or stainless steel) used for tribocharging predict these expected results. However, ultraviolet photoelectron spectroscopy (UPS) measurements in air on specimens of three different coal species, showed the work function to be approximately 5.4 eV, which is higher than a reported measured work function of 3.93 eV. Studies by UPS and x-ray photoelectron spectroscopy on copper, stainless steel, aluminum, and other commonly used tribocharging materials such as nylon and polytetrafluorethylene, as well as pure pyrite, showed that the work function varied considerably as a function of surface composition. Therefore, the reason for the bipolar charging of the coal particles may be the too small differences in work functions between coal powder and copper used as the charging material. The choice of a material for impaction triboelectric charging for coal or mineral separation should therefore depend upon the actual work function as modified by the ambient conditions such as moisture content and the oxidation of the surface

  15. X-ray diffraction

    International Nuclear Information System (INIS)

    Einstein, J.R.; Wei, C.H.

    1982-01-01

    We have been interested in structural elucidation by x-ray diffraction of compounds of biological interest. Understanding exactly how atoms are arranged in three-dimensional arrays as molecules can help explain the relationship between structure and functions. The species investigated may vary in size and shape; our recent studies included such diverse substances as antischistosomal drugs, a complex of cadmium with nucleic acid base, nitrate salts of adenine, and proteins

  16. Probing deeper by hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Risterucci, P.; Renault, O., E-mail: olivier.renault@cea.fr; Martinez, E.; Delaye, V. [CEA, LETI, MINATEC Campus, 38054 Grenoble Cedex 09 (France); Detlefs, B. [CEA, LETI, MINATEC Campus, 38054 Grenoble Cedex 09 (France); European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Zegenhagen, J. [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Gaumer, C. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles (France); Grenet, G. [Institut des Nanotechnologies de Lyon (INL), UMR CNRS 5270, Ecole Centrale de Lyon, 36, avenue Guy de Collongue 69 134 Ecully Cedex (France); Tougaard, S. [Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230 Odense M (Denmark)

    2014-02-03

    We report an hard x-ray photoelectron spectroscopy method combining high excitation energy (15 keV) and improved modelling of the core-level energy loss features. It provides depth distribution of deeply buried layers with very high sensitivity. We show that a conventional approach relying on intensities of the core-level peaks is unreliable due to intense plasmon losses. We reliably determine the depth distribution of 1 ML La in a high-κ/metal gate stack capped with 50 nm a-Si. The method extends the sensitivity of photoelectron spectroscopy to depths beyond 50 nm.

  17. Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

    Energy Technology Data Exchange (ETDEWEB)

    Patanen, M.; Benkoula, S.; Nicolas, C.; Goel, A. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Antonsson, E. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Physikalische und Theoretische Chemie Institut für Chemie und Biochemie, Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin (Germany); Neville, J. J. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick E3B 6E2 (Canada); Miron, C., E-mail: Catalin.Miron@synchrotron-soleil.fr [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Extreme Light Infrastructure - Nuclear Physics (ELI-NP), ‘Horia Hulubei’ National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125 Măgurele, Jud. Ilfov (Romania)

    2015-09-28

    Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters’ surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface.

  18. Sources of polarized neutrons

    International Nuclear Information System (INIS)

    Walter, L.

    1983-01-01

    Various sources of polarized neutrons are reviewed. Monoenergetic source produced with unpolarized or polarized beams, white sources of polarized neutrons, production by transmissions through polarized hydrogen targets and polarized thermal neutronsare discussed, with appropriate applications included. (U.K.)

  19. 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

    beam qualities) and liquid microjet technology recently enabled the first liquid interface PES experiments in the IR/UV-pump and extreme ultraviolet-probe (EUV-probe) configuration. In this Account, we highlight features of the technology and a number of recent applications, including extreme states of matter and the discovery and detection of short-lived transients of the solvated electron in water. Properties of the EUV radiation, such as its controllable polarization and features of the liquid microjet, will enable unique experiments in the near future. PES measures electron binding energies and angular distributions of photoelectrons, which comprise unique information about electron orbitals and their involvement in chemical bonding. One of the future goals is to use this information to trace molecular orbitals, over time, in chemical reactions or biological transformations.

  20. Unitary bases for x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Patterson, C.W.; Harter, W.G.; Schneider, W.D.

    1979-01-01

    A Gelfand basis is used to derive the coefficients of fractional parentage (CFP's) used to calculate intensities for x-ray photoelectron spectroscopy of atoms. Using associated Gelfand bases, we show that it is easy to derive the Racah CFP relations between particles and holes

  1. Energy- and angled-resolved photoelectron spectroscopy of negative ions

    International Nuclear Information System (INIS)

    Pegg, D.J.; Thompson, J.S.; Compton, R.N.; Alton, G.D.

    1988-01-01

    Energy- and angle-resolved photoelectron detachment spectroscopy is currently being used to investigate the structure of negative ions and their interaction with radiation. Measurements of the electron affinity of the Ca atom and the partial cross sections for photodetachment of the metastable negative ion, He - (1s2s2p 4 P), are reported. 5 refs., 5 figs

  2. Graphene defect formation by extreme ultraviolet generated photoelectrons

    NARCIS (Netherlands)

    Gao, An; Lee, Christopher James; Bijkerk, Frederik

    2014-01-01

    We have studied the effect of photoelectrons on defect formation in graphene during extreme ultraviolet (EUV) irradiation. Assuming the major role of these low energy electrons, we have mimicked the process by using low energy primary electrons. Graphene is irradiated by an electron beam with energy

  3. Photoelectron spectroscopic studies of some transition metals and alloys

    International Nuclear Information System (INIS)

    McLachlan, A.D.

    1974-01-01

    Photoelectron spectra of polycrystalline samples of Cu, Ag and Au at photon energies of 21.22, 40.81 eV and 1487 eV were measured. The corrected 40.81 eV results were compared to theoretical band structure calculations and monochromatized x-ray photoelectron results. Correlation of hitherto unresolved peaks in the 40.81 eV spectra was observed. Comparison of the relative intensities of the spectral d bands and the theoretical calculations revealed discrepancies which were assigned to matrix element modulation effects in the photoelectron emission process. Experimental measurements and theories of the electronic structure of disordered alloy systems were reviewed. The 21.22 eV and 40.81 eV photoelectron spectra of some AgPd and AgAu alloys were measured. The spectra were compared with previous x-ray photon results, and with theoretical calculations based on the Coherent Potential Approximation (CPA) model of disordered alloy systems. The present results were found to give more clearly defined spectral details, with differences in the comparison reflecting the simplifying assumptions of the CPA calculation. (author)

  4. Characterization of Ge-nanocrystal films with photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Bostedt, C.; Buuren, T. van; Willey, T.M.; Nelson, A.J.; Franco, N.; Moeller, T.; Terminello, L.J.

    2003-01-01

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

  5. X-ray and photoelectron spectroscopy of light rare earths

    International Nuclear Information System (INIS)

    Fuggle, J.C.

    1983-01-01

    Core level photoelectron spectroscopy, X-ray absorption spectroscopy, bremsstrahlung isochromat spectroscopy and valence band studies are discussed. Particular emphasis is placed on cerium. Correlation effects, multiplet structure, screening effects and the dynamics of the processes involved are illustrated with selected examples. (Auth.)

  6. Diffractive interference optical analyzer (DiOPTER)

    Science.gov (United States)

    Sasikumar, Harish; Prasad, Vishnu; Pal, Parama; Varma, Manoj M.

    2016-03-01

    This report demonstrates a method for high-resolution refractometric measurements using, what we have termed as, a Diffractive Interference Optical Analyzer (DiOpter). The setup consists of a laser, polarizer, a transparent diffraction grating and Si-photodetectors. The sensor is based on the differential response of diffracted orders to bulk refractive index changes. In these setups, the differential read-out of the diffracted orders suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6x10-7 RIU was achieved in glass. This work focuses on devices with integrated sample well, made on low-cost PDMS. As the detection methodology is experimentally straightforward, it can be used across a wide array of applications, ranging from detecting changes in surface adsorbates via binding reactions to estimating refractive index (and hence concentration) variations in bulk samples. An exciting prospect of this technique is the potential integration of this device to smartphones using a simple interface based on transmission mode configuration. In a transmission configuration, we were able to achieve an LoD of 4x10-4 RIU which is sufficient to explore several applications in food quality testing and related fields. We are envisioning the future of this platform as a personal handheld optical analyzer for applications ranging from environmental sensing to healthcare and quality testing of food products.

  7. Diffraction by disordered polycrystalline fibers

    International Nuclear Information System (INIS)

    Stroud, W.J.; Millane, R.P.

    1995-01-01

    X-ray diffraction patterns from some polycrystalline fibers show that the constituent microcrystallites are disordered. The relationship between the crystal structure and the diffracted intensities is then quite complicated and depends on the precise kind and degree of disorder present. The effects of disorder on diffracted intensities must be included in structure determinations using diffraction data from such specimens. Theory and algorithms are developed here that allow the full diffraction pattern to be calculated for a disordered polycrystalline fiber made up of helical molecules. The model accommodates various kinds of disorder and includes the effects of finite crystallite size and cylindrical averaging of the diffracted intensities from a fiber. Simulations using these methods show how different kinds, or components, of disorder produce particular diffraction effects. General properties of disordered arrays of helical molecules and their effects on diffraction patterns are described. Implications for structure determination are discussed. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Niedermaier, Inga; Kolbeck, Claudia; Steinrück, Hans-Peter; Maier, Florian, E-mail: florian.maier@fau.de [Lehrstuhl für Physikalische Chemie II, FAU Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen (Germany)

    2016-04-15

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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.

  10. X-ray diffraction

    International Nuclear Information System (INIS)

    Vries, J.L. de.

    1976-01-01

    The seventh edition of Philips' Review of literature on X-ray diffraction begins with a list of conference proceedings on the subject, organised by the Philips' organisation at regular intervals in various European countries. This is followed by a list of bulletins. The bibliography is divided according to the equipment (cameras, diffractometers, monochromators) and its applications. The applications are subdivided into sections for high/low temperature and pressure, effects due to the equipment, small angle scattering and a part for stress, texture and phase analyses of metals and quantitative analysis of minerals

  11. Developments in diffraction databases

    International Nuclear Information System (INIS)

    Jenkins, R.

    1999-01-01

    Full text: There are a number of databases available to the diffraction community. Two of the more important of these are the Powder Diffraction File (PDF) maintained by the International Centre for Diffraction Data (ICDD), and the Inorganic Crystal Structure Database (ICSD) maintained by Fachsinformationzentrum (FIZ, Karlsruhe). In application, the PDF has been used as an indispensable tool in phase identification and identification of unknowns. The ICSD database has extensive and explicit reference to the structures of compounds: atomic coordinates, space group and even thermal vibration parameters. A similar database, but for organic compounds, is maintained by the Cambridge Crystallographic Data Centre. These databases are often used as independent sources of information. However, little thought has been given on how to exploit the combined properties of structural database tools. A recently completed agreement between ICDD and FIZ, plus ICDD and Cambridge, provides a first step in complementary use of the PDF and the ICSD databases. The focus of this paper (as indicated below) is to examine ways of exploiting the combined properties of both databases. In 1996, there were approximately 76,000 entries in the PDF and approximately 43,000 entries in the ICSD database. The ICSD database has now been used to calculate entries in the PDF. Thus, to derive d-spacing and peak intensity data requires the synthesis of full diffraction patterns, i.e., we use the structural data in the ICSD database and then add instrumental resolution information. The combined data from PDF and ICSD can be effectively used in many ways. For example, we can calculate PDF data for an ideally random crystal distribution and also in the absence of preferred orientation. Again, we can use systematic studies of intermediate members in solid solutions series to help produce reliable quantitative phase analyses. In some cases, we can study how solid solution properties vary with composition and

  12. Polarization study

    International Nuclear Information System (INIS)

    Nurushev, S.B.

    1989-01-01

    Brief review is presented of the high energy polarization study including experimental data and the theoretical descriptions. The mostimportant proposals at the biggest accelerators and the crucial technical developments are also listed which may become a main-line of spin physics. 35 refs.; 10 figs.; 4 tabs

  13. Polar Stratigraphy

    Science.gov (United States)

    1999-01-01

    These three images were taken on three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough. The left and right images are separated by a distance of more than 100 kilometers (62 miles). Note the similar layers in each image.

  14. Diffractive DIS: Where are we?

    International Nuclear Information System (INIS)

    Nikolaev, N.N.

    2001-01-01

    A brief review of the modern QCD theory of diffractive DIS is given. The recent progress has been remarkably rapid, all the principal predictions from the color dipole approach to diffraction - the (Q 2 + m V 2 ) scaling, the pattern of SCHNC, shrinkage of the diffraction cone in hard diffractive DIS, the strong impact of longitudinal gluons in inclusive J/Ψ production at Tevatron - have been confirmed experimentally

  15. Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. II. Molecular-frame and recoil-frame photoelectron angular distributions

    DEFF Research Database (Denmark)

    Lebech, M.; Houver, J.C.; Raseev, G.

    2012-01-01

    Experimental and theoretical results for molecular-frame photoemission are presented for inner-valence shell photoionization of the CO molecule induced by linearly and circularly polarized light. The experimental recoil frame photoelectron angular distributions (RFPADs) obtained from dissociative...... photoionization measurements where the velocities of the ionic fragment and photoelectron were detected in coincidence, are compared to RFPADs computed using the multichannel Schwinger configuration interaction method. The formalism for including a finite lifetime of the predissociative ion state is presented...... for the case of general elliptically polarized light, to obtain the RFPAD rather than the molecular frame photoelectron angular distribution (MFPAD), which would be obtained with the assumption of instantaneous dissociation. We have considered photoionization of CO for the photon energies of 26.0 eV, 29.5 e...

  16. Ionization of oriented carbonyl sulfide molecules by intense circularly polarized laser pulses

    DEFF Research Database (Denmark)

    Dimitrovski, Darko; Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction of the molec......We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction......-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons. In the following article [Phys. Rev. A 83, 023406 (2011)] the focus is to understand strong-field ionization from three-dimensionally-oriented asymmetric top molecules, in particular the suppression of electron...

  17. Probing hot-electron effects in wide area plasmonic surfaces using X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ayas, Sencer; Cupallari, Andi; Dana, Aykutlu, E-mail: aykutlu@unam.bilkent.edu.tr [UNAM Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey)

    2014-12-01

    Plasmon enhanced hot carrier formation in metallic nanostructures increasingly attracts attention due to potential applications in photodetection, photocatalysis, and solar energy conversion. Here, hot-electron effects in nanoscale metal-insulator-metal (MIM) structures are investigated using a non-contact X-ray photoelectron spectroscopy based technique using continuous wave X-ray and laser excitations. The effects are observed through shifts of the binding energy of the top metal layer upon excitation with lasers of 445, 532, and 650 nm wavelength. The shifts are polarization dependent for plasmonic MIM grating structures fabricated by electron beam lithography. Wide area plasmonic MIM surfaces fabricated using a lithography free route by the dewetting of evaporated Ag on HfO{sub 2} exhibit polarization independent optical absorption and surface photovoltage. Using a simple model and making several assumptions about the magnitude of the photoemission current, the responsivity and external quantum efficiency of wide area plasmonic MIM surfaces are estimated as 500 nA/W and 11 × 10{sup −6} for 445 nm illumination.

  18. Stabilization of polar Mn3O4(001) film on Ag(001): Interplay between kinetic and structural stability

    Science.gov (United States)

    Kundu, Asish K.; Barman, Sukanta; Menon, Krishnakumar S. R.

    2017-10-01

    Stabilization processes of polar surfaces are often very complex and interesting. Understanding of these processes is crucial as it ultimately determines the properties of the film. Here, by the combined study of Low Energy Electron Diffraction (LEED), X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoemission Spectroscopy (UPS) techniques we show that, although there can be many processes involved in the stabilization of the polar surfaces, in case of Mn3O4(001)/Ag(001), it goes through different reconstructions of the Mn2O4 terminated surface which is in good agreements with the theoretical predictions. The complex surface phase diagram has been probed by LEED as a function of film thickness, oxygen partial pressure and substrate temperature during growth, while their chemical compositions have been probed by XPS. Below a critical film thickness of ∼ 1 unit cell height (8 sublayers or 3 ML) of Mn3O4 and oxygen partial pressure range of 2 × 10-8 mbar oxygen partial pressure (> 5 × 10-7 mbar) and higher temperature UHV annealing. The origin of these stripes has been explained with the help of UPS results.

  19. The PhotoElectron Boundary as observed by MAVEN instruments

    Science.gov (United States)

    Garnier, P.; Steckiewicz, M.; Mazelle, C. X.; Xu, S.; Mitchell, D. L.; Holmberg, M.; Halekas, J. S.; Andersson, L.; Brain, D.; Connerney, J. E. P.; Espley, J. R.; Lillis, R. J.; Luhmann, J. G.; Savaud, J. A.; Jakosky, B. M.

    2017-12-01

    Photoelectron peaks in the 20-30 eV energy range are commonly observed in planetary atmospheres (Earth, Mars, Titan...), produced by the intense photoionization from solar 30.4 nm photons. At Mars, these photoelectrons result from the ionization of CO2 and O atmospheric neutrals, and are known to escape the planet down its tail, making them tracers for the atmospheric escape (Frahm et al., 2006). Furthermore, their presence or absence allows us to define the so-called PhotoElectron Boundary (PEB), that separates the sunlit photoelectron-dominated ionosphere from the solar wind controlled environment, as initially observed by the Mars Global Surveyor (MGS) MAG/ER instrument (Mitchell et al. (2000, 2001). We provide here a detailed statistical analysis of the location and properties of the PEB based on the Mars Atmosphere and Volatile Evolution (MAVEN) mission electron and magnetic field data. Our dataset includes 1696 dayside PEB crossings obtained from September 2014 until May 2016 (the observations of escaping photoelectrons in the wake being not included). The PEB appears as mostly sensitive to the solar wind dynamic and crustal magnetic fields pressures, for which a quantitative dependance is derived and compared with two other important boundaries : the bow shock and magnetic pileup boundary. The PEB altitude is highly variable, leading to a variable wake cross section for escape (up to +- 50%), which is important for deriving global escape rates from in situ photoelectron escape rates. The PEB is not always sharp, and is, despite a strong variability, characterized on average by : a magnetic field topology typical for the edge of the Magnetic Pile Up Region above it, more field aligned fluxes above than below, and a clear change of the altitude dependence of both electron fluxes and total density (that appears different from the ionopause). The PEB thus appears as a transition region between two plasma and field configurations which is determined by the

  20. Diffraction anomalous fine structure using X-ray anomalous dispersion

    International Nuclear Information System (INIS)

    Soejima, Yuji; Kuwajima, Shuichiro

    1998-01-01

    A use of X-ray anomalous dispersion effects for structure investigation has recently been developed by using synchrotron radiation. One of the interesting method is the observation of anomalous fine structure which arise on diffraction intensity in energy region of incident X-ray at and higher than absorption edge. The phenomenon is so called Diffraction Anomalous Fine Structure (DAFS). DAFS originates in the same physical process an that of EXAFS: namely photoelectric effect at the corresponding atom and the interaction of photoelectron waves between the atom and neighboring atoms. In contrast with EXAFS, the method is available for only the crystalline materials, but shows effective advantages of the structure investigations by a use of diffraction: one is the site selectivity and the other is space selectivity. In the present study, demonstrations of a use of X-ray anomalous dispersion effect for the superstructure determination will be given for the case of PbZrO 3 , then recent trial investigations of DAFS in particular on the superlattice reflections will be introduced. In addition, we discuss about Forbidden Reflection near Edge Diffraction (FRED) which is more recently investigated as a new method of the structure analysis. (author)

  1. Diffraction and Unitarity

    Science.gov (United States)

    Dremin, I. M.

    I begin with a tribute to V.N. Gribov and then come to a particular problem which would be of interest for him. His first paper on reggeology was devoted to elastic scatterings of hadrons. Here, using the unitarity relation in combination with experimental data about the elastic scattering in the diffraction cone, I show how the shape and the darkness of the interaction region of colliding protons change with the increase of their energies. In particular, the collisions become fully absorptive at small impact parameters at LHC energies that results in some special features of inelastic processes as well. The possible evolution with increasing energy of the shape from the dark core at the LHC to the fully transparent one at higher energies is discussed. It implies that the terminology of the black disk would be replaced by the black torus.

  2. Nanoscale photoelectron ionisation detector based on lanthanum hexaboride

    International Nuclear Information System (INIS)

    Zimmer, C.M.; Kunze, U.; Schubert, J.; Hamann, S.; Doll, T.

    2011-01-01

    A nanoscale ioniser is presented exceeding the limitation of conventional photoionisation detectors. It employs accelerated photoelectrons that allow obtaining molecule specificity by the tuning of ionisation energies. The material lanthanum hexaboride (LaB 6 ) is used as air stable photo cathode. Thin films of that material deposited by pulsed laser deposition (PLD) show quantum efficiency (QE) in the range of 10 -5 which is comparable to laser photo stimulation results. A careful treatment of the material yields reasonable low work functions even after surface reoxidation which opens up the possibility of using ultraviolet light emitting diodes (UV LEDs) in replacement of discharge lamps. Schematic diagram of a photoelectron ionisation detector (PeID) operating by an electron emitter based on the photoelectric effect of lanthanum hexaboride. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Photoelectron spectroscopy via electronic spectroscopy of molecular ions

    International Nuclear Information System (INIS)

    Khan, Z.H.

    1990-01-01

    In this work, a new aspect of the correlation between optical and photoelectron spectra is discussed on the basis of which the first ionization potentials of condensed-ring aromatics can be estimated from certain features in the electronic spectra of their positive ions. Furthermore, it is noticed that the first IP's are very sensitive to molecular size as the latter's inclusion in the regression formulas improves the results considerably. Once the first ionization potential for a molecule is determined, its higher IP's may be computed if the lower-energy electronic bands for its cation are known. This procedure is especially useful for such systems whose uv photoelectron spectra are unknown. (author). 11 refs, 10 figs, 1 tab

  4. Recent trends in spin-resolved photoelectron spectroscopy

    Science.gov (United States)

    Okuda, Taichi

    2017-12-01

    Since the discovery of the Rashba effect on crystal surfaces and also the discovery of topological insulators, spin- and angle-resolved photoelectron spectroscopy (SARPES) has become more and more important, as the technique can measure directly the electronic band structure of materials with spin resolution. In the same way that the discovery of high-Tc superconductors promoted the development of high-resolution angle-resolved photoelectron spectroscopy, the discovery of this new class of materials has stimulated the development of new SARPES apparatus with new functions and higher resolution, such as spin vector analysis, ten times higher energy and angular resolution than conventional SARPES, multichannel spin detection, and so on. In addition, the utilization of vacuum ultra violet lasers also opens a pathway to the realization of novel SARPES measurements. In this review, such recent trends in SARPES techniques and measurements will be overviewed.

  5. High-order multiphoton ionization photoelectron spectroscopy of NO

    International Nuclear Information System (INIS)

    Carman, H.S. Jr.; Compton, R.N.

    1987-01-01

    Photoelectron energy 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 A 2 Σ + (v=O) level yielded a distribution of electron energies corresponding to all accessible vibrational levels (v + =O-6) of the nascent ion. Angular distributions of electrons corresponding to v + =O and v + =3 were significantly different. The 3 + 2 REMPI via the A 2 Σ + (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. 4 refs., 3 figs

  6. Effect of plasma instability on F region photoelectron distributions

    International Nuclear Information System (INIS)

    Bloomberg, H.W.

    1975-01-01

    Ionospheric suprathermal photoelectrons have relatively large cross sections for selected energies. In particular, electrons with energies of about 2.5 eV strongly excite nitrogen vibrational modes, while metastable states of oxygen are excited at about 5 eV. Thus an energy distribution based on chemical kinetic considerations give rise to a maximum at around 4 eV in the F region below 250 km. However, rocket experiments have shown that the expected peaks in the flux spectrum are relatively weak. This discrepancy is explained by the development of a linear instability leading to a wave-particle interaction. The linear mode is driven by the photoelectrons near the 4-eV maximum in the presence of a magnetic field. The effect is shown to be ineffective at sufficiently low altitudes, where collisionless theory fails. (auth)

  7. Effect of plasma instability on F region photoelectron distributions

    International Nuclear Information System (INIS)

    Bloomberg, H.W.

    1975-01-01

    Ionospheric suprathermal photoelectrons have relatively large cross sections for selected energies. In particular, electrons with energies of about 2.5 eV strongly excite nitrogen vibrational modes, while metastable states of oxygen are excited at about 5 eV. Thus an energy distribution based on chemical kinetic considerations gives rise to a maximum at around 4 eV in the F region below 250 km. However, rocket experiments have shown that the expected peaks in the flux spectrum are relatively weak. This discrepancy is explained by the development of a linear instability leading to a wave-particle interaction. the linear mode is driven by the photoelectrons near the 4-eV maximum in the presence of a magnetic field. The effect is shown to be ineffective at sufficiently low altitudes, where collisionless theory fails

  8. Effect of collisions on photoelectron sheath in a gas

    Science.gov (United States)

    Sodha, Mahendra Singh; Mishra, S. K.

    2016-02-01

    This paper presents a study of the effect of the collision of electrons with atoms/molecules on the structure of a photoelectron sheath. Considering the half Fermi-Dirac distribution of photo-emitted electrons, an expression for the electron density in the sheath has been derived in terms of the electric potential and the structure of the sheath has been investigated by incorporating Poisson's equation in the analysis. The method of successive approximations has been used to solve Poisson's equation with the solution for the electric potential in the case of vacuum, obtained earlier [Sodha and Mishra, Phys. Plasmas 21, 093704 (2014)], being used as the zeroth order solution for the present analysis. The inclusion of collisions influences the photoelectron sheath structure significantly; a reduction in the sheath width with increasing collisions is obtained.

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

    International Nuclear Information System (INIS)

    Wang, Lai-sheng; Niu, B.; Lee, Y.T.; Shirley, D.A.

    1989-07-01

    High resolution HeI (580 angstrom) photoelectron spectra of As 2 , As 4 , and P 4 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 2 E and 2 T 2 states of P 4 + and As 4 + . As a result of the Jahn-Teller effect, the 2 E state splits into two bands, and the 2 T 2 state splits into three bands, in combination with the spin-orbit effect. It was observed that the ν 2 normal vibrational mode was involved in the vibronic interaction of the 2 E state, while both the ν 2 and ν 3 modes were active in the 2 T 2 state. 26 refs., 5 figs., 3 tabs

  10. Boundary diffraction wave integrals for diffraction modeling of external occulters

    OpenAIRE

    Cady, E.

    2012-01-01

    An occulter is a large diffracting screen which may be flown in conjunction with a telescope to image extrasolar planets. The edge is shaped to minimize the diffracted light in a region beyond the occulter, and a telescope may be placed in this dark shadow to view an extrasolar system with the starlight removed. Errors in position, orientation, and shape of the occulter will diffract additional light into this region, and a challenge of modeling an occulter system is to accurately and quickly...

  11. Attosecond polarization control in atomic RABBITT-like experiments assisted by a circularly polarized laser

    Science.gov (United States)

    Boll, D. I. R.; Fojón, O. A.

    2017-12-01

    We study theoretically the single ionization of noble gas atoms by the combined action of an attosecond pulse train with linear polarization and an assistant laser field with circular polarization. We employ a non-perturbative model that under certain approximations gives closed-form expressions for the angular distributions of photoelectrons. Interestingly, our model allow us to interpret these angular distributions as two-centre interferences where the orientation and the modulus of the separation vector between the virtual emitters is governed by the assistant laser field. Additionally, we show that such a configuration of light fields is similar to the polarization control technique, where both the attosecond pulse train and the assistant laser field have linear polarizations whose relative orientation may be controlled. Moreover, in order to compare our results with the available experimental data, we obtain analytical expressions for the cross sections integrated over the photoelectron emission angles. By means of these expressions, we define the ‘magic time’ as the delay for which the total cross sections for atomic targets exhibit the same functional form as the one of the monochromatic photoionization of diatomic molecular targets.

  12. Operation of a Langmuir Probe in a Photoelectron Plasma

    International Nuclear Information System (INIS)

    Dove, Adrienne; Robertson, Scott; Horanyi, Mihaly; Poppe, Andrew; Wang Xu

    2011-01-01

    Dust transport on the lunar surface is likely facilitated by the variable electric fields that are generated by changing plasma conditions. We have developed an experimental apparatus to study lunar photoelectric phenomena and gain a better understanding of the conditions controlling dust transport. As an initial step, Langmuir probe measurements are used to characterize the photoelectron plasma produced above a Zr surface, and these techniques will be extended to CeO 2 and lunar simulant surfaces.

  13. Total reflection X-ray photoelectron spectroscopy: A review

    International Nuclear Information System (INIS)

    Kawai, Jun

    2010-01-01

    Total reflection X-ray photoelectron spectroscopy (TRXPS) is reviewed and all the published papers on TRXPS until the end of 2009 are included. Special emphasis is on the historical development. Applications are also described for each report. The background reduction is the most important effect of total reflection, but interference effect, relation to inelastic mean free path, change of probing depth are also discussed.

  14. Asymmetric photoelectron angular distributions from interfering photoionization processes

    International Nuclear Information System (INIS)

    Yin, Y.; Chen, C.; Elliott, D.S.; Smith, A.V.

    1992-01-01

    We have measured asymmetric photoelectron angular distributions for atomic rubidium. Ionization is induced by a one-photon interaction with 280 nm light and by a two-photon interaction with 560 nm light. Interference between the even- and odd-parity free-electron wave functions allows us to control the direction of maximum electron flux by varying the relative phase of the two laser fields

  15. Recent applications of hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weiland, Conan; Woicik, Joseph C., E-mail: Joseph.Woicik@NIST.gov [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Rumaiz, Abdul K. [National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973 (United States); Pianetta, Piero [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2016-05-15

    Recent applications of hard x-ray photoelectron spectroscopy (HAXPES) demonstrate its many capabilities in addition to several of its limitations. Examples are given, including measurement of buried interfaces and materials under in situ or in operando conditions, as well as measurements under x-ray standing-wave and resonant excitation. Physical considerations that differentiate HAXPES from photoemission measurements utilizing soft x-ray and ultraviolet photon sources are also presented.

  16. Time-resolved photoelectron spectrometry of a dephasing process in pyrazine

    International Nuclear Information System (INIS)

    Pavlov, R.L.; Pavlov, L.I.; Delchev, Ya.I.; Pavlova, S.I.

    2001-01-01

    The first femtosecond time-resolved photoelectron imaging (PEI) is presented. The method is characterized by photoionization of NO and further applied to ultrafast dephasing in pyrazine. Intermediate case behaviour in radiationless transition is clearly observed in time-resolved photoelectron kinetic energy distribution. Femtosecond PEI is with much improved efficiency than conventional photoelectron spectroscopies. It is anticipated that the unifield approach of time-resolved photoelectron and photoion imaging opens the possibility of observing photon-induced dynamics in real time

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

    International Nuclear Information System (INIS)

    Bodi, Andras; Johnson, Melanie; Gerber, Thomas; Gengeliczki, Zsolt; Sztaray, Balint; Baer, Tomas

    2009-01-01

    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 10 3 -10 7 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.

  18. Diffraction studies on the origin of giant magneto-electric effects in multiferroics

    International Nuclear Information System (INIS)

    Arima, Taka-hisa

    2009-01-01

    Magnetic ferroelectrics termed multiferroics often exhibit a giant magneto-electric response such as an appearance, disappearance, and rotation of ferroelectric polarization by the application of a magnetic field. In most multiferroics, long-wavelength spiral magnetic order arises from the competition among some magnetic exchange interactions. Spin-polarized neutron diffraction studies reveal that the ferroelectric polarization direction corresponds to the helicity of spiral magnetism. A change in magnetic order with the application of a magnetic field has been investigated for various multiferroics by means of synchrotron x-ray diffraction, because it can provide us some information about the periodicity and type of magnetic order. (author)

  19. Polarization holograms allow highly efficient generation of complex light beams.

    Science.gov (United States)

    Ruiz, U; Pagliusi, P; Provenzano, C; Volke-Sepúlveda, K; Cipparrone, Gabriella

    2013-03-25

    We report a viable method to generate complex beams, such as the non-diffracting Bessel and Weber beams, which relies on the encoding of amplitude information, in addition to phase and polarization, using polarization holography. The holograms are recorded in polarization sensitive films by the interference of a reference plane wave with a tailored complex beam, having orthogonal circular polarizations. The high efficiency, the intrinsic achromaticity and the simplicity of use of the polarization holograms make them competitive with respect to existing methods and attractive for several applications. Theoretical analysis, based on the Jones formalism, and experimental results are shown.

  20. Diffraction radiation from relativistic particles

    CERN Document Server

    Potylitsyn, Alexander Petrovich; Strikhanov, Mikhail Nikolaevich; Tishchenko, Alexey Alexandrovich

    2010-01-01

    This book deals with diffraction radiation, which implies the boundary problems of electromagnetic radiation theory. Diffraction radiation is generated when a charged particle moves in a vacuum near a target edge. Diffraction radiation of non-relativistic particles is widely used to design intense emitters in the cm wavelength range. Diffraction radiation from relativistic charged particles is important for noninvasive beam diagnostics and design of free electron lasers based on Smith-Purcell radiation which is diffraction radiation from periodic structures. Different analytical models of diffraction radiation and results of recent experimental studies are presented in this book. The book may also serve as guide to classical electrodynamics applications in beam physics and electrodynamics. It can be of great use for young researchers to develop skills and for experienced scientists to obtain new results.

  1. Diffraction radiation from relativistic particles

    International Nuclear Information System (INIS)

    Potylitsyn, Alexander Petrovich; Ryazanov, Mikhail Ivanovich; Strikhanov, Mikhail Nikolaevich; Tishchenko, Alexey Alexandrovich

    2010-01-01

    This book deals with diffraction radiation, which implies the boundary problems of electromagnetic radiation theory. Diffraction radiation is generated when a charged particle moves in a vacuum near a target edge. Diffraction radiation of non-relativistic particles is widely used to design intense emitters in the cm wavelength range. Diffraction radiation from relativistic charged particles is important for noninvasive beam diagnostics and design of free electron lasers based on Smith-Purcell radiation which is diffraction radiation from periodic structures. Different analytical models of diffraction radiation and results of recent experimental studies are presented in this book. The book may also serve as guide to classical electrodynamics applications in beam physics and electrodynamics. It can be of great use for young researchers to develop skills and for experienced scientists to obtain new results. (orig.)

  2. Gaussian beam diffraction in weakly anisotropic inhomogeneous media

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsov, Yu.A., E-mail: kravtsov@am.szczecin.p [Institute of Physics, Maritime University of Szczecin, Szczecin 70-500 (Poland); Space Research Institute, Russian Academy of Science, Moscow 117 997 (Russian Federation); Berczynski, P., E-mail: pawel.berczynski@ps.p [Institute of Physics, West Pomeranian University of Technology, Szczecin 70-310 (Poland); Bieg, B., E-mail: b.bieg@am.szczecin.p [Institute of Physics, Maritime University of Szczecin, Szczecin 70-500 (Poland)

    2009-08-10

    Combination of quasi-isotropic approximation (QIA) of geometric optics with paraxial complex geometric optics (PCGO) is suggested, which allows describing both diffraction and polarization evolution of Gaussian electromagnetic beams in weakly anisotropic inhomogeneous media. Combination QIA/PCGO reduces Maxwell equations to the system of the ordinary differential equations of the first order and radically simplifies solution of various problems, related to microwave plasma diagnostics, including plasma polarimetry, interferometry and refractometry in thermonuclear reactors. Efficiency of the method is demonstrated by the example of electromagnetic beam diffraction in a linear layer of magnetized plasma with parameters, modeling tokamak plasma in the project ITER.

  3. Gaussian beam diffraction in weakly anisotropic inhomogeneous media

    International Nuclear Information System (INIS)

    Kravtsov, Yu.A.; Berczynski, P.; Bieg, B.

    2009-01-01

    Combination of quasi-isotropic approximation (QIA) of geometric optics with paraxial complex geometric optics (PCGO) is suggested, which allows describing both diffraction and polarization evolution of Gaussian electromagnetic beams in weakly anisotropic inhomogeneous media. Combination QIA/PCGO reduces Maxwell equations to the system of the ordinary differential equations of the first order and radically simplifies solution of various problems, related to microwave plasma diagnostics, including plasma polarimetry, interferometry and refractometry in thermonuclear reactors. Efficiency of the method is demonstrated by the example of electromagnetic beam diffraction in a linear layer of magnetized plasma with parameters, modeling tokamak plasma in the project ITER.

  4. Polar Polygons

    Science.gov (United States)

    2005-01-01

    18 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-outlined polygons on a frost-covered surface in the south polar region of Mars. In summer, this surface would not be bright and the polygons would not have dark outlines--these are a product of the presence of seasonal frost. Location near: 77.2oS, 204.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  5. CMS results on hard diffraction

    CERN Document Server

    INSPIRE-00107098

    2013-01-01

    In these proceedings we present CMS results on hard diffraction. Diffractive dijet production in pp collisions at $\\sqrt{s}$=7 TeV is discussed. The cross section for dijet production is presented as a function of $\\tilde{\\xi}$, representing the fractional momentum loss of the scattered proton in single-diffractive events. The observation of W and Z boson production in events with a large pseudo-rapidity gap is also presented.

  6. Causal aspects of diffraction

    International Nuclear Information System (INIS)

    Crawford, G.N.

    1981-01-01

    The analysis is directed at a causal description of photon diffraction, which is explained in terms of a wave exerting real forces and providing actual guidance to each quantum of energy. An undulatory PSI wave is associated with each photon, and this wave is assumed to imply more than an informative probability function, so that it actually carries real energy, in much the same way as does an electro-magnetic wave. Whether or not it may be in some way related to the electromagnetic wave is left as a matter of on-going concern. A novel application of the concept of a minimum energy configuration is utilized; that is, a system of energy quanta seeks out relative positions and orientations of least mutual energy, much as an electron seeks its Bohr radius as a position of least mutual energy. Thus the concept implies more a guiding interaction of the PSI waves than an interfering cancellation of these waves. Similar concepts have been suggested by L. de Broglie and D. Bohm

  7. Study of optical Laue diffraction

    International Nuclear Information System (INIS)

    Chakravarthy, Giridhar; Allam, Srinivasa Rao; Satyanarayana, S. V. M.; Sharan, Alok

    2014-01-01

    We present the study of the optical diffraction pattern of one and two-dimensional gratings with defects, designed using desktop pc and printed on OHP sheet using laser printer. Gratings so prepared, using novel low cost technique provides good visual aid in teaching. Diffraction pattern of the monochromatic light (632.8nm) from the grating so designed is similar to that of x-ray diffraction pattern of crystal lattice with point defects in one and two-dimensions. Here both optical and x-ray diffractions are Fraunhofer. The information about the crystalline lattice structure and the defect size can be known

  8. Gluon radiation in diffractive electroproduction

    International Nuclear Information System (INIS)

    Buchmueller, W.; McDermott, M.F.; Hebecker, A.

    1996-07-01

    Order α s -correlations to the diffractive structure functions F L D and F 2 D at large Q 2 and small x are evaluated in the semiclassical approach, where the initial proton is treated as a classical colour field. The diffractive final state contains a fast gluon in addition to a quark-antiquark pair. Two of these partons may have large transverse momentum. Our calculations lead to an intuitive picture of deep-inelastic diffractive processes which is very similar to Bjorken's aligned-jet model. Both diffractive structure functions contain leading twist contributions from high-p perpendicular to jets. (orig.)

  9. Study of optical Laue diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Chakravarthy, Giridhar, E-mail: cgiridhar84@gmail.com, E-mail: aloksharan@email.com; Allam, Srinivasa Rao, E-mail: cgiridhar84@gmail.com, E-mail: aloksharan@email.com; Satyanarayana, S. V. M., E-mail: cgiridhar84@gmail.com, E-mail: aloksharan@email.com; Sharan, Alok, E-mail: cgiridhar84@gmail.com, E-mail: aloksharan@email.com [Department of Physics, Pondicherry University, Puducherry-605014 (India)

    2014-10-15

    We present the study of the optical diffraction pattern of one and two-dimensional gratings with defects, designed using desktop pc and printed on OHP sheet using laser printer. Gratings so prepared, using novel low cost technique provides good visual aid in teaching. Diffraction pattern of the monochromatic light (632.8nm) from the grating so designed is similar to that of x-ray diffraction pattern of crystal lattice with point defects in one and two-dimensions. Here both optical and x-ray diffractions are Fraunhofer. The information about the crystalline lattice structure and the defect size can be known.

  10. Radially Polarized Conical Beam from an Embedded Etched Fiber

    OpenAIRE

    Kalaidji , D.; Spajer , M.; Marthouret , N.; Grosjean , T.

    2009-01-01

    International audience; We propose a method for producing a conical beam based on the lateral refraction of the TM01 mode from a two-mode fiber after chemical etching of the cladding, and for controlling its radial polarization. The whole power of the guided mode is transferred to the refracted beam with low diffraction. Polarization control by a series of azimuthal detectors and a stress controller affords the transmission of a stabilized radial polarization through an optical fiber. A solid...

  11. Strategic Polarization.

    Science.gov (United States)

    Kalai, Adam; Kalai, Ehud

    2001-08-01

    In joint decision making, similarly minded people may take opposite positions. Consider the example of a marriage in which one spouse gives generously to charity while the other donates nothing. Such "polarization" may misrepresent what is, in actuality, a small discrepancy in preferences. It may be that the donating spouse would like to see 10% of their combined income go to charity each year, while the apparently frugal spouse would like to see 8% donated. A simple game-theoretic analysis suggests that the spouses will end up donating 10% and 0%, respectively. By generalizing this argument to a larger class of games, we provide strategic justification for polarization in many situations such as debates, shared living accommodations, and disciplining children. In some of these examples, an arbitrarily small disagreement in preferences leads to an arbitrarily large loss in utility for all participants. Such small disagreements may also destabilize what, from game-theoretic point of view, is a very stable equilibrium. Copyright 2001 Academic Press.

  12. Diffractive optics and nanophotonics resolution below the diffraction limit

    CERN Document Server

    Minin, Igor

    2016-01-01

    In this book the authors present several examples of techniques used to overcome the Abby diffraction limit using flat and 3D diffractive optical elements, photonic crystal lenses, photonic jets, and surface plasmon diffractive optics. The structures discussed can be used in the microwave and THz range and also as scaled models for optical frequencies. Such nano-optical microlenses can be integrated, for example, into existing semiconductor heterostructure platforms for next-generation optoelectronic applications. Chapter 1 considers flat diffractive lenses and innovative 3D radiating structures including a conical millimeter-wave Fresnel zone plate (FZP) lens proposed for subwavelength focusing. In chapter 2 the subwavelength focusing properties of diffractive photonic crystal lenses are considered and it is shown that at least three different types of photonic crystal lens are possible.  With the aim of achieving subwavelength focusing, in chapter 3 an alternative mechanism to produce photonic jets at Tera...

  13. p/n-Polarity of thiophene oligomers in photovoltaic cells: role of molecular vs. supramolecular properties.

    Science.gov (United States)

    Ghosh, Tanwistha; Gopal, Anesh; Saeki, Akinori; Seki, Shu; Nair, Vijayakumar C

    2015-04-28

    Molecular and supramolecular properties play key roles in the optoelectronic properties and photovoltaic performances of organic materials. In the present work, we show how small changes in the molecular structure affect such properties, which in turn control the intrinsic and fundamental properties such as the p/n-polarity of organic semiconductors in bulk-heterojunction solar cells. Herein, we designed and synthesized two acceptor-donor-acceptor type semiconducting thiophene oligomers end-functionalized with oxazolone/isoxazolone derivatives (OT1 and OT2 respectively). The HOMO-LUMO energy levels of both derivatives were found to be positioned in such a way that they can act as electron acceptors to P3HT and electron donors to PCBM. However, OT1 functions as a donor (with PCBM) and OT2 as an acceptor (with P3HT) in BHJ photovoltaic cells, and their reverse roles results in either no or poor performance of the cells. Detailed studies using UV-vis absorption and fluorescence spectroscopy, time-correlated single photon counting, UV-photoelectron spectroscopy, density functional theory calculations, X-ray diffraction, and thermal gravimetric analysis proved that both molecular and supramolecular properties contributed equally but in a contrasting manner to the abovementioned observation. The obtained results were further validated by flash-photolysis time-resolved microwave conductivity studies which showed an excellent correlation between the structure, property, and device performances of the materials.

  14. Electron diffraction from carbon nanotubes

    International Nuclear Information System (INIS)

    Qin, L-C

    2006-01-01

    The properties of a carbon nanotube are dependent on its atomic structure. The atomic structure of a carbon nanotube can be defined by specifying its chiral indices (u, v), that specify its perimeter vector (chiral vector), with which the diameter and helicity are also determined. The fine electron beam available in a modern transmission electron microscope (TEM) offers a unique probe to reveal the atomic structure of individual nanotubes. This review covers two aspects related to the use of the electron probe in the TEM for the study of carbon nanotubes: (a) to understand the electron diffraction phenomena for inter-pretation of the electron diffraction patterns of carbon nanotubes and (b) to obtain the chiral indices (u, v), of the carbon nanotubes from the electron diffraction patterns. For a nanotube of a given structure, the electron scattering amplitude from the carbon nanotube is first described analytically in closed form using the helical diffraction theory. From a known structure as given by the chiral indices (u, v), its electron diffraction pattern can be calculated and understood. The reverse problem, i.e. assignment of the chiral indices from an electron diffraction pattern of a carbon nanotube, is approached from the relationship between the electron scattering intensity distribution and the chiral indices (u, v). We show that electron diffraction patterns can provide an accurate and unambiguous assignment of the chiral indices of carbon nanotubes. The chiral indices (u, v) can be read indiscriminately with a high accuracy from the intensity distribution on the principal layer lines in an electron diffraction pattern. The symmetry properties of electron diffraction from carbon nanotubes and the electron diffraction from deformed carbon nanotubes are also discussed in detail. It is shown that 2mm symmetry is always preserved for single-walled carbon nanotubes, but it can break down for multiwalled carbon nanotubes under some special circumstances

  15. 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.

  16. Tolerance analysis on diffraction efficiency and polychromatic integral diffraction efficiency for harmonic diffractive optics

    Science.gov (United States)

    Shan, Mao

    2016-10-01

    In this dissertation, the mathematical model of effect of manufacturing errors including microstructure relative height error and relative width error on diffraction efficiency for the harmonic diffractive optical elements (HDEs) is set up. According to the expression of the phase delay and diffraction efficiency of the HDEs, the expression of diffraction efficiency of refraction and diffractive optical element with the microstructure height and periodic width errors in fabrication process is presented in this paper. Furthermore, the effect of manufacturing errors on diffraction efficiency for the harmonic diffractive optical elements is studied, and diffraction efficiency change is analyzed as the relative microstructure height-error in the same and in the opposite sign as well as relative width-error in the same and in the opposite sign. Example including infrared wavelength with materials GE has been discussed in this paper. Two kinds of manufacturing errors applied in 3.7 4.3um middle infrared and 8.7-11.5um far infrared optical system which results in diffraction efficiency and PIDE of HDEs are studied. The analysis results can be used for manufacturing error control in micro-structure height and periodic width. Results can be used for HDEs processing.

  17. Probing long-range structural order in SnPc/Ag(111) by umklapp process assisted low-energy angle-resolved photoelectron spectroscopy

    Science.gov (United States)

    Jauernik, Stephan; Hein, Petra; Gurgel, Max; Falke, Julian; Bauer, Michael

    2018-03-01

    Laser-based angle-resolved photoelectron spectroscopy is performed on tin-phthalocyanine (SnPc) adsorbed on silver Ag(111). Upon adsorption of SnPc, strongly dispersing bands are observed which are identified as secondary Mahan cones formed by surface umklapp processes acting on photoelectrons from the silver substrate as they transit through the ordered adsorbate layer. We show that the photoemission data carry quantitative structural information on the adsorbate layer similar to what can be obtained from a conventional low-energy electron diffraction (LEED) study. More specifically, we compare photoemission data and LEED data probing an incommensurate-to-commensurate structural phase transition of the adsorbate layer. Based on our results we propose that Mahan-cone spectroscopy operated in a pump-probe configuration can be used in the future to probe structural dynamics at surfaces with a temporal resolution in the sub-100-fs regime.

  18. Computer Simulation of Diffraction Patterns.

    Science.gov (United States)

    Dodd, N. A.

    1983-01-01

    Describes an Apple computer program (listing available from author) which simulates Fraunhofer and Fresnel diffraction using vector addition techniques (vector chaining) and allows user to experiment with different shaped multiple apertures. Graphics output include vector resultants, phase difference, diffraction patterns, and the Cornu spiral…

  19. Polarized secondary radioactive beams

    International Nuclear Information System (INIS)

    Zaika, N.I.

    1992-01-01

    Three methods of polarized radioactive nuclei beam production: a) a method nuclear interaction of the non-polarized or polarized charged projectiles with target nuclei; b) a method of polarization of stopped reaction radioactive products in a special polarized ion source with than following acceleration; c) a polarization of radioactive nuclei circulating in a storage ring are considered. Possible life times of the radioactive ions for these methods are determined. General schemes of the polarization method realizations and depolarization problems are discussed

  20. Polar crane

    International Nuclear Information System (INIS)

    Makosinski, S.

    1981-01-01

    In many applications polar cranes have to be repeatedly positioned with high accuracy. A guidance system is disclosed which has two pairs of guides. Each guide consists of two rollers carried by a sheave rotatable mounted on the crane bridge, the rollers being locatable one on each side of a guideway, e.g. the circular track on which the bridge runs. The pairs of guides are interconnected by respective rope loops which pass around and are locked to the respective pairs of sheaves in such a manner that movement of one guide results in equal movement of the other guide in a sense to maintain the repeatability of positioning of the centre of the bridge. A hydraulically-linked guide system is also described. (author)

  1. Time-resolved photoelectron spectroscopy using synchrotron radiation time structure

    International Nuclear Information System (INIS)

    Bergeard, N.; Silly, M.G.; Chauvet, C.; Guzzo, M.; Ricaud, J.P.; Izquierdo, M.; Sirotti, F.; Krizmancic, D.; Guzzo, M.; Stebel, L.; Pittana, P.; Sergo, R.; Cautero, G.; Dufour, G.; Rochet, F.

    2011-01-01

    Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photo emitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station. (authors)

  2. Stability and performance studies of the PITZ photoelectron gun

    International Nuclear Information System (INIS)

    Isaev, Igor

    2018-02-01

    The invention of free electron lasers (FELs) opened new opportunities for the investigation of natural phenomena. However, the operation of a FEL requires high energy, high peak current electron beams with very small transverse emittance which causes extreme requirements for the corresponding electron sources. Besides the high beam quality, the electron sources must have very high operational stability and reliability. One of the electron source types which satisfy FEL requirements is a photoelectron gun. Photoelectron guns combine photoemissive electron generation and direct acceleration in a Radio Frequency (RF) cavity. The Photo Injector Test facility at DESY, Zeuthen site (PITZ), was established as a test stand of the electron source for FELs like FLASH and the European XFEL in Hamburg. The studies of the beam emittance at PITZ showed that the gun is able to produce electron beams with emittance even smaller than it is required by XFEL specifications. But the experiments on the emittance revealed discrepancies between expected gun behavior and observation, such as the difference in optimal parameters for the smallest emittance value, asymmetry of the transverse beam profile and the phase spaces. The work performed at PITZ includes preparation of several RF guns for their subsequent operation at FLASH and the European XFEL. RF conditioning of a gun cavity is one of the major steps of the preparation of a high brightness electron source required for modern FELs. A thorough procedure is applied to increase the peak and average RF power in the gun cavity, including an increase of the repetition rate and RF pulse length combined with a gun solenoid current sweep. The main goals of this thesis are: (1) an attempt of deep understanding of physical processes taking place during operation of a photoelectron gun (conditioning process, parameters adjustments); (2) definition of operational problems sources and explanation of the experimentally obtained results in the gun

  3. Recent developments in photoelectron dynamics using synchrotron radiation

    International Nuclear Information System (INIS)

    Carlson, T.A.; Krause, M.O.; Taylor, J.W.; Keller, P.R.; Piancastelli, M.N.; Grimm, F.A.; Whitley, T.A.

    1982-01-01

    Through a collaborative effort of members of the Oak Ridge National Laboratory and Universities of Wisconsin and Tennessee, a comprehensive study of atoms and molecules using angle-resolved photoelectron spectroscopy and synchrotron radiation is underway at the Synchrotron Radiation Center, Stoughton, Wisconsin. Over 50 molecules and atoms have been investigated. These results, coupled with theory, aim at a better understanding of the dynamics of photoionization and of the wave functions that control these processes. In particular, attention is given to the following topics: metal atomic vapors, generalization of molecular orbital types, autoionization, shape resonances, core shell effects, satellite structure, and the Cooper minimum

  4. Time-resolved photoelectron spectroscopy of nitrobenzene and its aldehydes

    Science.gov (United States)

    Schalk, Oliver; Townsend, Dave; Wolf, Thomas J. A.; Holland, David M. P.; Boguslavskiy, Andrey E.; Szöri, Milan; Stolow, Albert

    2018-01-01

    We report the first femtosecond time-resolved photoelectron spectroscopy study of 2-, 3- and 4-nitrobenzaldehyde (NBA) and nitrobenzene (NBE) in the gas phase upon excitation at 200 nm. In 3- and 4-NBA, the dynamics follow fast intersystem crossing within 1-2 picoseconds. In 2-NBA and NBE, the dynamics are faster (∼ 0.5 ps). 2-NBA undergoes hydrogen transfer similar to solution phase dynamics. NBE either releases NO2 in the excited state or converts internally back to the ground state. We discuss why these channels are suppressed in the other nitrobenzaldehydes.

  5. Electronic structure and photoelectron spectra of boron beta-diketonates

    International Nuclear Information System (INIS)

    Borisenko, A.V.; Vovna, V.I.

    1990-01-01

    Photoelectron spectra and data of semiempirical (MNDO, CNDO/2, CNDO/S, INDO) and nonempirical (with STO-3G basis) methods of calculation were obtained to analyse the electronic structure of boron-containing diketonate cycle and the influence of substitution effect (aromatic substituents in particular) on it. The sequence and the character of upper occupied MO were determined; the nature of bond of the fragment X 2 B + and AA was established; charges of six-membered ion and influence of substituents on their values were determined. 13 refs.; 5 figs.; 4 tabs

  6. Geometry Optimization of DC/RF Photoelectron Gun

    CERN Document Server

    Chen Ping; Yu, David

    2005-01-01

    Pre-acceleration of photoelectrons in a pulsed, high voltage, short, dc gap and its subsequent injection into an rf gun is a promising method to improve electron beam emittance in rf accelerators. Simulation work has been performed in order to optimize the geometric shapes of a dc/rf gun and improve electron beam properties. Variations were made on cathode and anode shapes, dc gap distance, and inlet shape of the rf cavity. Simulations showed that significant improvement on the normalized emittance (< 1 mm-mrad), compared to a dc gun with flat cathode, could be obtained after the geometric shapes of the gun were optimized.

  7. Single-photoelectron noise reduction in scintillation detectors

    International Nuclear Information System (INIS)

    Marvin, T.P.

    1995-10-01

    The 1994--95 search at SLAC for mulicharged particles used four 21 x 21 x 130-cm 3 Bicron 408 scintillation counters to detect a signal at the single-photoelectron level. The competing noise requiring minimization was due to a combination of PM tube (8-inch Thorne EMI 9353KA) afterpulsing and ambient radiation-induced scintillator luminescence. A very slow decay (> 30 μs) component was observed and received particular attention. Efforts to reduce the SPE noise included photomultiplier tube base modifications, detector shielding and cooling, signal amplification, and veto procedures

  8. A photoelectron and TPEPICO investigation of the acetone radical cation.

    Science.gov (United States)

    Rennie, Emma E; Boulanger, Anne-Marie; Mayer, Paul M; Holland, David M P; Shaw, David A; Cooper, Louise; Shpinkova, Larisa G

    2006-07-20

    The valence shell photoelectron spectrum, threshold photoelectron spectrum, and threshold photoelectron photoion coincidence (TPEPICO) mass spectra of acetone have been measured using synchrotron radiation. New vibrational progressions have been observed and assigned in the X 2B2 state photoelectron bands of acetone-h6 and acetone-d6, and the influence of resonant autoionization on the threshold electron yield has been investigated. The dissociation thresholds for fragment ions up to 31 eV have been measured and compared to previous values. In addition, kinetic modeling of the threshold region for CH3* and CH4 loss leads to new values of 78 +/- 2 kJ mol(-1) and 75 +/- 2 kJ mol(-1), respectively, for the 0 K activation energies for these two processes. The result for the methyl loss channel is in reasonable agreement with, but slightly lower than, that of 83 +/- 1 kJ mol(-1) derived in a recent TPEPICO study by Fogleman et al. The modeling accounts for both low-energy dissociation channels at two different ion residence times in the mass spectrometer. Moreover, the effects of the ro-vibrational population distribution, the electron transmission efficiency, and the monochromator band-pass are included. The present activation energies yield a Delta(f)H298 for CH3CO+ of 655 +/- 3 kJ mol(-1), which is 4 kJ mol(-1) lower than that reported by Fogleman et al. The present Delta(f)H298 for CH3CO+ can be combined with the Delta(f)H298 for CH2CO (-47.5 +/- 1.6 kJ mol(-1)) and H+ (1530 kJ mol(-1)) to yield a 298 K proton affinity for ketene of 828 +/- 4 kJ mol(-1), in good agreement with the value (825 kJ mol(-1)) calculated at the G2 level of theory. The measured activation energy for CH4 loss leads to a Delta(f)H298 (CH2CO+*) of 873 +/- 3 kJ mol(-1).

  9. Stability and performance studies of the PITZ photoelectron gun

    Energy Technology Data Exchange (ETDEWEB)

    Isaev, Igor

    2018-02-15

    The invention of free electron lasers (FELs) opened new opportunities for the investigation of natural phenomena. However, the operation of a FEL requires high energy, high peak current electron beams with very small transverse emittance which causes extreme requirements for the corresponding electron sources. Besides the high beam quality, the electron sources must have very high operational stability and reliability. One of the electron source types which satisfy FEL requirements is a photoelectron gun. Photoelectron guns combine photoemissive electron generation and direct acceleration in a Radio Frequency (RF) cavity. The Photo Injector Test facility at DESY, Zeuthen site (PITZ), was established as a test stand of the electron source for FELs like FLASH and the European XFEL in Hamburg. The studies of the beam emittance at PITZ showed that the gun is able to produce electron beams with emittance even smaller than it is required by XFEL specifications. But the experiments on the emittance revealed discrepancies between expected gun behavior and observation, such as the difference in optimal parameters for the smallest emittance value, asymmetry of the transverse beam profile and the phase spaces. The work performed at PITZ includes preparation of several RF guns for their subsequent operation at FLASH and the European XFEL. RF conditioning of a gun cavity is one of the major steps of the preparation of a high brightness electron source required for modern FELs. A thorough procedure is applied to increase the peak and average RF power in the gun cavity, including an increase of the repetition rate and RF pulse length combined with a gun solenoid current sweep. The main goals of this thesis are: (1) an attempt of deep understanding of physical processes taking place during operation of a photoelectron gun (conditioning process, parameters adjustments); (2) definition of operational problems sources and explanation of the experimentally obtained results in the gun

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

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2009-01-01

    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 background and gain......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...

  11. Precise analysis of the metal package photomultiplier single photoelectron spectra

    International Nuclear Information System (INIS)

    Chirikov-Zorin, I.E.; Fedorko, I.; Sykora, I.; Tokar, S.; Menzione, A.

    2000-01-01

    A deconvolution method based on a sophisticated photomultiplier response function was used to analyse the compact metal package photomultiplier spectra taken in single photoelectron mode. The spectra taken by Hamamtsu R5600 and R5900 photomultipliers have been analysed. The detailed analysis shows that the method appropriately describes the process of charge multiplication in these photomultipliers in a wide range of working regimes and the deconvoluted parameters are established with about 1% accuracy. The method can be used for a detailed analysis of photomultiplier noise and for calibration purposes

  12. Automation of an X-ray photoelectron spectrometer

    International Nuclear Information System (INIS)

    Ashury, M.R.

    2003-02-01

    The Institute of Solid State Physics of the Vienna University of Technology is established with an X-ray Photoelectron Spectrometer Kratos XSAM 800. In its original state the instrument enables measurements of photoelectron spectra in a semiautomatical mode. After mounting of the specimen an eventual surface cleaning by argon ion sputtering is possible. Next steps are setting of x-ray tube high voltage and current, start energy and energy range of spectrum and time of measurement. Data are obtained by an x-t plotter and evaluations are performed from the registration charts. If necessary, measured spectra have to be digitized by means of a scanner. In the Introduction of this thesis the principle of X-ray photoelectron spectrometry is treated including a number of practical examples. It shows that an automation allows an extension of the performance of the instrument. Details are remote controlled experiments, wider energy ranges with improved energy resolution. Furthermore, the digitized data treatment enables background subtration, determination of line positions and integrated signal strengths, and is the detection of lowlevel of lines (the peak with lowamplitude) possible. A further advantage is the computer assisted documentation and comparison of results from different specimens. After this description of the essential requirements different possible solutions of an automation are discussed. Thus, it is decided to develop a completely new hardware for a perfect control of the spectrometer. A further decision is to be made on the most efficient kind of micro processor. From the considerations follows a completely new control board with a transputer as multi tasking processor. The complete control unit consists of a digital system, an analog system and a power unit. The digital system controls settings and spectra accumulation and includes the transputer board, the pc-link card, the i/o-card and the step scanning control board. The analog system controls the

  13. Accuracy of single photoelectron time spread measurement of fast photomultipliers

    International Nuclear Information System (INIS)

    Leskovar, B.

    1975-01-01

    The accuracy of time spread measurements of fast photomultipliers was investigated, using single photoelectrons. The effect of the finite light pulse width on the measurement accuracy was determined and discussed. Experimental data were obtained on a special measuring system for light pulse widths ranging from 200 psec to 10 nsec, using fast photomultipliers 8850 and C31024 with optimized operating conditions for minimum transit time spread. A modified exponential function expression and curve-fitting parameters are given, which fit closely the experimentally obtained data over a wide dynamic range of light pulse widths. (U.S.)

  14. Electron optics development for photo-electron spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Wannberg, Bjoern [VG Scienta AB, P.O. Box 15120, SE-750 15 Uppsala (Sweden); BW Particle Optics AB, P.O. Box 55, SE-822 22 Alfta (Sweden)], E-mail: bjorn@particleoptics.se

    2009-03-21

    The demand for simultaneous observation of photo-electron distributions in several dimensions has made the hemispherical deflection analyzer (HDA) and the time-of-flight (TOF) analyzer the dominating spectrometer types. Some common limiting factors for resolution and sensitivity are considered. Recent developments of the HDA and its lens system which increase the energy range and angular acceptance are described. The properties of a recently developed angle-resolving TOF system (AR-TOF) are also described. The possibility to avoid integration losses in energy or angular resolution by applying non-linear mappings of the primary data is discussed.

  15. Electron optics development for photo-electron spectrometers

    International Nuclear Information System (INIS)

    Wannberg, Bjoern

    2009-01-01

    The demand for simultaneous observation of photo-electron distributions in several dimensions has made the hemispherical deflection analyzer (HDA) and the time-of-flight (TOF) analyzer the dominating spectrometer types. Some common limiting factors for resolution and sensitivity are considered. Recent developments of the HDA and its lens system which increase the energy range and angular acceptance are described. The properties of a recently developed angle-resolving TOF system (AR-TOF) are also described. The possibility to avoid integration losses in energy or angular resolution by applying non-linear mappings of the primary data is discussed.

  16. Monochromatization of synchrotron radiation for studies in photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Murty, P.S.

    1981-01-01

    Synchrotron radiation provides a tunable photon source which bridges the wavelength gap between HeI and AlKsub(α) radiation sources in photoelectron spectroscopy. The essential component for using synchrotron radiation is a monochromator. Some design features of the monochromators fabricated at Stanford, U.S.A., and Orsay, France, are described. The Stanford monochromator is a silicon crystal monochromator yielding 8 keV X-ray beam and is used with SPEAR storage ring facility, while the Orsay monochromator is a grazing incidence grating monochromator used for UPS studies. (M.G.B.)

  17. Characterization of Colloidal Quantum Dot Ligand Exchange by X-ray Photoelectron Spectroscopy

    Science.gov (United States)

    Atewologun, Ayomide; Ge, Wangyao; Stiff-Roberts, Adrienne D.

    2013-05-01

    Colloidal quantum dots (CQDs) are chemically synthesized semiconductor nanoparticles with size-dependent wavelength tunability. Chemical synthesis of CQDs involves the attachment of long organic surface ligands to prevent aggregation; however, these ligands also impede charge transport. Therefore, it is beneficial to exchange longer surface ligands for shorter ones for optoelectronic devices. Typical characterization techniques used to analyze surface ligand exchange include Fourier-transform infrared spectroscopy, x-ray diffraction, transmission electron microscopy, and nuclear magnetic resonance spectroscopy, yet these techniques do not provide a simultaneously direct, quantitative, and sensitive method for evaluating surface ligands on CQDs. In contrast, x-ray photoelectron spectroscopy (XPS) can provide nanoscale sensitivity for quantitative analysis of CQD surface ligand exchange. A unique aspect of this work is that a fingerprint is identified for shorter surface ligands by resolving the regional XPS spectrum corresponding to different types of carbon bonds. In addition, a deposition technique known as resonant infrared matrix-assisted pulsed laser evaporation is used to improve the CQD film uniformity such that stronger XPS signals are obtained, enabling more accurate analysis of the ligand exchange process.

  18. X-ray photoelectron spectroscopy investigation of the carburization of 310 stainless steel

    International Nuclear Information System (INIS)

    Tabet, N.; Allam, I.; Yin, R.C.

    2003-01-01

    The surface of 310 stainless steel (310SS) samples was investigated by X-ray photoelectron spectroscopy (XPS) after 500 h cyclic exposure to two carburizing atmospheres: CH 4 (2%)-H 2 (98%) at 800 deg. C, and CH 4 (10%)-H 2 (90%) at 1100 deg. C. The depth distribution of various elements in the surface region was obtained by XPS after successive cycles of argon etching. The microstructure of the alloy was observed by scanning electron microscopy (SEM) and the phases formed during the exposure were analyzed by X-ray diffraction (XRD). The results showed that the major phases that were formed within few micrometer depth during exposure at 800 deg. C include both iron and chromium carbides. (Mn, Cr) oxide was also formed as a result of the reaction with the residual oxygen of the atmosphere. A region of few microns width that was relatively depleted of chromium was formed under the surface as a result of the outwards diffusion of chromium. The exposure to the reducing atmosphere at 1100 deg. C led to the formation of various iron and chromium carbides. No oxide was formed during exposure. In all exposed samples, the surface was Cr enriched while nickel remained buried under the surface region that reacted with the atmosphere

  19. Microscopic work function anisotropy and surface chemistry of 316L stainless steel using photoelectron emission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, N., E-mail: nick.barrett@cea.fr [CEA, IRAMIS, SPEC, LENSIS, F-91191 Gif-sur-Yvette (France); Renault, O. [CEA, LETI, Minatec Campus, F-38054 Grenoble Cedex 09 (France); Lemaître, H. [Université de Cergy-Pontoise, Rue d’Eragny, Neuville sur Oise, 95 031 Cergy-Pontoise (France); Surface Dynamics Laboratory, Institut for Fysik og Astronomi Aarhus Universitet, Ny Munkegade 120, 8000 Aarhus C (Denmark); Bonnaillie, P. [CEA, DEN, DANS, DMN, SRMP, F-91191 Gif-sur-Yvette (France); Barcelo, F. [CEA, DEN, DANS, DMN, SRMA, LA2M, F-91191 Gif-sur-Yvette (France); Miserque, F. [CEA, DEN, DANS, DPC, SCCME, LECA, F-91191 Gif-sur-Yvette (France); Wang, M.; Corbel, C. [Laboratoire des Solides Irradis, Ecole Polytechnique, route de Saclay, F-91128 Palaiseau (France)

    2014-08-15

    Highlights: • PEEM and EBSD study of spatial variations in local work function of 316L steel. • Correlation between work function and crystal grain orientation at the surface of 316L steel. • Spatially resolved chemistry of residual oxide layer. - Abstract: We have studied the variation in the work function of the surface of sputtered cleaned 316L stainless steel with only a very thin residual oxide surface layer as a function of grain orientation using X-ray photoelectron emission microscopy (XPEEM) and Electron Backscattering Diffraction. The grains are mainly oriented [1 1 1] and [1 0 1]. Four distinct work function values spanning a 150 meV energy window are measured. Grains oriented [1 1 1] have a higher work function than those oriented [1 0 1]. From core level XPEEM we deduce that all grain surfaces are Cr enriched and Ni depleted whereas the Cr/Fe ratio is similar for all grains. The [1 1 1] oriented grains show evidence for a Cr{sub 2}O{sub 3} surface oxide and a higher concentration of defective oxygen sites.

  20. X-ray photoelectron spectroscopy study of the metal/cermet interface

    International Nuclear Information System (INIS)

    Lu Hua; Shen Dianhong; Xue Qikun

    2001-01-01

    Interfacial reactions between aluminium and polycrystalline cermet TiC 0.6 were investigated using x-ray photo-electron spectroscopy, Auger electron spectroscopy and x-ray diffraction. It was found that titanium exists in two chemical states. The carbide and oxide of titanium can be detected simultaneously, and the atomic ratio of Ti:C:O is 5:3:2. This suggests that TiC 0.6 is a Ti-oxycarbide or oxygenated Tic composite: Ti 5 C 3 O 2 (TiO 2 + 4TiC 0.75 ). When Al is deposited in vacuum on the Ti-oxycarbide surface, the active Al atoms react chemically only with TiO 2 at room temperature, but not with TiC 0.75 in Ti-oxycarbide. The reaction products are Al 2 O 3 and the intermetallic compound Al 3 Ti. Annealing the Al/TiC 0.6 interface at 750 degree C, Al reacts also with TiC 0.75 to form a brittle Al 4 C 3 phase

  1. Profiling pleural effusion cells by a diffraction imaging method

    Science.gov (United States)

    Al-Qaysi, Safaa; Hong, Heng; Wen, Yuhua; Lu, Jun Q.; Feng, Yuanming; Hu, Xin-Hua

    2018-02-01

    Assay of cells in pleural effusion (PE) is an important means of disease diagnosis. Conventional cytology of effusion samples, however, has low sensitivity and depends heavily on the expertise of cytopathologists. We applied a polarization diffraction imaging flow cytometry method on effusion cells to investigate their features. Diffraction imaging of the PE cell samples has been performed on 6000 to 12000 cells for each effusion cell sample of three patients. After prescreening to remove images by cellular debris and aggregated non-cellular particles, the image textures were extracted with a gray level co-occurrence matrix (GLCM) algorithm. The distribution of the imaged cells in the GLCM parameters space was analyzed by a Gaussian Mixture Model (GMM) to determine the number of clusters among the effusion cells. These results yield insight on textural features of diffraction images and related cellular morphology in effusion samples and can be used toward the development of a label-free method for effusion cells assay.

  2. Achieving optimum diffraction based overlay performance

    Science.gov (United States)

    Leray, Philippe; Laidler, David; Cheng, Shaunee; Coogans, Martyn; Fuchs, Andreas; Ponomarenko, Mariya; van der Schaar, Maurits; Vanoppen, Peter

    2010-03-01

    Diffraction Based Overlay (DBO) metrology has been shown to have significantly reduced Total Measurement Uncertainty (TMU) compared to Image Based Overlay (IBO), primarily due to having no measurable Tool Induced Shift (TIS). However, the advantages of having no measurable TIS can be outweighed by increased susceptibility to WIS (Wafer Induced Shift) caused by target damage, process non-uniformities and variations. The path to optimum DBO performance lies in having well characterized metrology targets, which are insensitive to process non-uniformities and variations, in combination with optimized recipes which take advantage of advanced DBO designs. In this work we examine the impact of different degrees of process non-uniformity and target damage on DBO measurement gratings and study their impact on overlay measurement accuracy and precision. Multiple wavelength and dual polarization scatterometry are used to characterize the DBO design performance over the range of process variation. In conclusion, we describe the robustness of DBO metrology to target damage and show how to exploit the measurement capability of a multiple wavelength, dual polarization scatterometry tool to ensure the required measurement accuracy for current and future technology nodes.

  3. Vectorial diffraction properties of THz vortex Bessel beams.

    Science.gov (United States)

    Wu, Zhen; Wang, Xinke; Sun, Wenfeng; Feng, Shengfei; Han, Peng; Ye, Jiasheng; Yu, Yue; Zhang, Yan

    2018-01-22

    A vortex Bessel beam combines the merits of an optical vortex and a Bessel beam, including a spiral wave front and a non-diffractive feature, which has immense application potentials in optical trapping, optical fabrication, optical communications, and so on. Here, linearly and circularly polarized vortex Bessel beams in the terahertz (THz) frequency range are generated by utilizing a THz quarter wave plate, a spiral phase plate, and Teflon axicons with different opening angles. Taking advantage of a THz focal-plane imaging system, vectorial diffraction properties of the THz vortex Bessel beams are comprehensively characterized and discussed, including the transverse (Ex, Ey) and longitudinal (Ez) polarization components. The experimental phenomena are accurately simulated by adopting the vectorial Rayleigh diffraction integral. By varying the opening angle of the axicon, the characteristic parameters of these THz vortex Bessel beams are exhibited and compared, including the light spot size, the diffraction-free range, and the phase evolution process. This work provides the precise experimental and theoretical bases for the comprehension and application of a THz vortex Bessel beam.

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

    CERN Document Server

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

    2003-01-01

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

  5. Analysis of the laser photoelectron spectrum of CH-2

    International Nuclear Information System (INIS)

    Bunker, P.R.; Sears, T.J.

    1985-01-01

    We have simulated the photoelectron spectrum of CH - 2 using the model described previously [Sears and Bunker, J. Chem. Phys. 79, 5265 (1983)]. The optimization of the fit of the simulated spectrum to the recently observed spectrum of Lineberger and co-workers [J. Chem. Phys. 81, 1048 (1984) and preceding paper] has enabled us to determine the rotation-bending energy levels of triplet CH 2 over an energy range of more than 1 eV. It has also enabled us to determine that the rotational temperature of the CH - 2 in the experiment is 220 K and that, for v 2 = 1, the vibrational temperature is 680 K. For CH - 2 we determine that a/sub e/ = 103 0 and that ν 2 = 1230 cm -1 . The singlet--triplet splitting in methylene is determined to be 3150 +- 30 cm -1 (0.3905 +- 0.004 eV, 9.01 +- 0.09 kcal/mol) from the photoelectron spectrum, in excellent agreement with the more accurate value previously obtained from LMR spectroscopy [McKellar et al., J. Chem. Phys. 79, 5251 (1983)] of 3165 +- 20 cm -1 (0.3924 +- 0.0025 eV, 9.05 +- 0.06 kcal/mol), and the electron affinity of triplet CH 2 is determined to be 0.652 +- 0.006 eV

  6. Interpretation of intensities in electron-momentum and photoelectron spectroscopies

    International Nuclear Information System (INIS)

    McCarthy, I.E.

    1984-06-01

    Relative intensities for the photoelectron reaction on atoms and molecules are not related to structure calculations in the same way as those for the noncoplanar symmetric (e,2e) reaction. The photoelectron dipole matrix element is dependent on recoil momentum only through its unique relationship to the photon energy and is much harder to calculate for chemically-interesting momenta. Relative intensities for binary (e,2e) reactions are independent of total energy at high enough energies and strongly dependent on symmetry and recoil momentum, for which an intensity profile can be measured for values starting at zero. In comparing with structure calculations, binary (e,2e) intensities for low recoil momentum may be compared directly with pole strengths in calculations of the one-electron Green's function or corresponding configuration-interaction calculations. In the case of states within a single symmetry manifold the relative intensities will be independent of recoil momentum up to some maximum, usually at least a few atomic units

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

    International Nuclear Information System (INIS)

    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 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

  8. Photoelectron Emission Studies in CsBr at 257 nm

    International Nuclear Information System (INIS)

    Maldonado, Juan R.; Liu, Zhi; Sun, Yun; Pianetta, Piero A.; Pease, Fabian W.

    2006-01-01

    CsBr/Cr photocathodes were found [1,2] to meet the requirements of a multi-electron beam lithography system operating with a light energy of 4.8 eV (257nm). The fact that photoemission was observed with a light energy below the reported 7.3 eV band gap for CsBr was not understood. This paper presents experimental results on the presence of intra-band gap absorption sites (IBAS) in CsBr thin film photo electron emitters, and presents a model based on IBAS to explain the observed photoelectron emission behavior at energies below band gap. A fluorescence band centered at 330 nm with a FWHM of about 0.34 eV was observed in CsBr/Cr samples under 257 nm laser illumination which can be attributed to IBAS and agrees well with previously obtained synchrotron photoelectron spectra[1] from the valence band of CsBr films

  9. Grazing incidence diffraction : A review

    Energy Technology Data Exchange (ETDEWEB)

    Gilles, B [LTPCM, ENSEEG. St. Martin d` Heres. (France)

    1996-09-01

    Different Grazing Incidence Diffraction (GID) methods for the analysis of thin films and multilayer structures are reviewed in three sections: the reflectivity is developed in the first one, which includes the non-specular diffuse scattering. The second one is devoted to the extremely asymmetric Bragg diffraction and the third one to the in-plane Bragg diffraction. Analytical formulations of the scattered intensities are developed for each geometry, in the framework of the kinetical analysis as well as the dynamical theory. Experimental examples are given to illustrate the quantitative possibility of the GID techniques.

  10. Diffraction dissociation at the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Jenkovszky, Laszlo [Bogolyubov Institute for Theoretical Physics (BITP), Ukrainian National Academy of Sciences 14-b, Metrolohichna str., Kiev, 03680, Ukraine and Wigner Research Centre for Physics, Hungarian Academy of Sciences 1525 Budapest, POB 49 (Hungary); Orava, Risto [Institute of Physics, Division of Elementary Particle Physics, P.O. Box 64 (Gustaf Haellstroeminkatu 2a), FI-00014 University of Helsinki, Finland and CERN, CH-1211 Geneva 23 (Switzerland); Salii, Andrii [Bogolyubov Institute for Theoretical Physics (BITP), Ukrainian National Academy of Sciences 14-b, Metrolohichna str., Kiev, 03680 (Ukraine)

    2013-04-15

    We report on recent calculations of low missing mass single (SD) and double (DD) diffractive dissociation at LHC energies. The calculations are based on a dual-Regge model, dominated by a single Pomeron exchange. The diffractively excited states lie on the nucleon trajectory N*, appended by the isolated Roper resonance. Detailed predictions for the squared momentum transfer and missing mass dependence of the differential and integrated single-and double diffraction dissociation in the kinematical range of present and future LHC measurements are given.

  11. Diffraction dissociation at the LHC

    International Nuclear Information System (INIS)

    Jenkovszky, László; Orava, Risto; Salii, Andrii

    2013-01-01

    We report on recent calculations of low missing mass single (SD) and double (DD) diffractive dissociation at LHC energies. The calculations are based on a dual-Regge model, dominated by a single Pomeron exchange. The diffractively excited states lie on the nucleon trajectory N*, appended by the isolated Roper resonance. Detailed predictions for the squared momentum transfer and missing mass dependence of the differential and integrated single-and double diffraction dissociation in the kinematical range of present and future LHC measurements are given.

  12. The diffractive achromat full spectrum computational imaging with diffractive optics

    KAUST Repository

    Peng, Yifan

    2016-07-11

    Diffractive optical elements (DOEs) have recently drawn great attention in computational imaging because they can drastically reduce the size and weight of imaging devices compared to their refractive counterparts. However, the inherent strong dispersion is a tremendous obstacle that limits the use of DOEs in full spectrum imaging, causing unacceptable loss of color fidelity in the images. In particular, metamerism introduces a data dependency in the image blur, which has been neglected in computational imaging methods so far. We introduce both a diffractive achromat based on computational optimization, as well as a corresponding algorithm for correction of residual aberrations. Using this approach, we demonstrate high fidelity color diffractive-only imaging over the full visible spectrum. In the optical design, the height profile of a diffractive lens is optimized to balance the focusing contributions of different wavelengths for a specific focal length. The spectral point spread functions (PSFs) become nearly identical to each other, creating approximately spectrally invariant blur kernels. This property guarantees good color preservation in the captured image and facilitates the correction of residual aberrations in our fast two-step deconvolution without additional color priors. We demonstrate our design of diffractive achromat on a 0.5mm ultrathin substrate by photolithography techniques. Experimental results show that our achromatic diffractive lens produces high color fidelity and better image quality in the full visible spectrum. © 2016 ACM.

  13. 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.

  14. Polarization singularities of the object field of skin surface

    International Nuclear Information System (INIS)

    Angelsky, O V; Ushenko, A G; Ushenko, Yu A; Ushenko, Ye G

    2006-01-01

    The paper deals with the investigation of formation mechanisms of laser radiation polarization structure scattered by an optically thin surface layer of human skin in two registration zones: a boundary field and a far zone of Fraunhofer diffraction. The conditions of forming polarization singularities by such an object in the scattered radiation field have been defined. Statistical and fractal polarization structure of object fields of physiologically normal and pathologically changed skin has been studied. It has been shown that polarization singularities of radiation scattered by physiologically normal skin samples have a fractal coordinate structure. It is characteristic for fields of pathologically changed skin to have a statistical coordinate structure of polarization singularities in all diffraction zones

  15. Polarization dependent effects in photo-fragmentation dynamics of free molecules

    International Nuclear Information System (INIS)

    Mocellin, A.; Marinho, R.R.T.; Coutinho, L.H.; Burmeister, F.; Wiesner, K.; Naves de Brito, A.

    2003-01-01

    We present multicoincidence spectra of nitrogen, formic acid and methyl methacrylate. We demonstrate how to probe the local symmetry of molecular orbitals from molecules core excited with linearly polarized synchrotron radiation. The intensity distribution of the photoelectron photo-ion photo-ion coincidence (PEPIPICO) spectrum reflects the selectivity and localization of core excitation by polarized light. By simulating the spectra the angular dependence of the fragmentation is determined

  16. Polarization dependent effects in photo-fragmentation dynamics of free molecules

    Energy Technology Data Exchange (ETDEWEB)

    Mocellin, A.; Marinho, R.R.T.; Coutinho, L.H.; Burmeister, F.; Wiesner, K.; Naves de Brito, A

    2003-04-01

    We present multicoincidence spectra of nitrogen, formic acid and methyl methacrylate. We demonstrate how to probe the local symmetry of molecular orbitals from molecules core excited with linearly polarized synchrotron radiation. The intensity distribution of the photoelectron photo-ion photo-ion coincidence (PEPIPICO) spectrum reflects the selectivity and localization of core excitation by polarized light. By simulating the spectra the angular dependence of the fragmentation is determined.

  17. Angle-resolved photoelectron spectroscopy of the chloro-substituted methanes

    Science.gov (United States)

    Keller, P. R.; Taylor, J. W.; Carlson, Thomas A.; Grimm, F. A.

    1983-09-01

    The angular distribution parameter, β, was determined for the valence orbitals (IP ' 21.2 eV) of CCl 4, CHCl 3, CH 2Cl 2, and CH 3Cl in the 10-30 eV photon energy range using dispersed polarized synchrotron radiation. The energy dependence of β in the photoelectron energy range of 2 to 10 eV for the non-bonding chlorine n(Cl) orbitals of these molecules was found to be similar for all n(Cl) orbitals investigated. The energy dependence of β for the σ orbitals in these molecules was similar to that observed previously for other σ orbitals. The experimental CCl 4 results were compared with theoretical CCl 4 results obtained using the Xα multiple scattering formalism. Theory predicts the existence of two strong shape resonances in each of the valence orbitals of CCl 4. The overall agreement between experiment and theory is evaluated along with the experimental evidence concerning the verification of the predicted shape resonances.

  18. Effects of spin-orbit activated interchannel coupling on dipole photoelectron angular distribution asymmetry parameters

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Baltenkov, A S [Arifov Institute of Electronics, Tashkent 70125 (Uzbekistan); Chernysheva, L V [A F Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Felfli, Z [Center for Theoretical Studies of Physics Systems, Clark Atlanta University, Atlanta, GA 30314 (United States); Manson, S T [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States); Msezane, A Z [Center for Theoretical Studies of Physics Systems, Clark Atlanta University, Atlanta, GA 30314 (United States)

    2004-02-28

    The effects of spin-orbit induced interchannel coupling on the dipole photoelectron angular asymmetry parameter {beta}{sub 3d} for Xe, Cs and Ba are explored using a modified version of the spin-polarized random phase approximation with exchange (SPRPAE) methodology. For Xe, {beta}{sub 3d{sub 5/2}} is modified somewhat by the interchannel coupling in the vicinity of the 3d{sub 3/2} {yields} {epsilon}f shape resonance, and this effect is significantly more pronounced in Cs where the resonance is larger. In Ba, however, where f-wave orbital collapse has occurred, the shape resonance has moved below threshold and the effect of interchannel coupling on {beta}{sub 3d{sub 5/2}} above the 3d{sub 3/2} threshold is negligible. But below the 3d{sub 3/2} threshold, {beta}{sub 3d{sub 5/2}} is dominated by the huge broad 3d{sub 3/2} {yields} 4f resonance.

  19. Diffraction by a grating made of a uniaxial dielectric-magnetic medium exhibiting negative refraction

    Energy Technology Data Exchange (ETDEWEB)

    Depine, Ricardo A [Grupo de Electromagnetismo Aplicado, Departamento de FIsica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); Lakhtakia, Akhlesh [CATMAS-Computational and Theoretical Materials Sciences Group, Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802-6812 (United States); Department of Physics, Imperial College, London SW7 2BZ (United Kingdom)

    2005-08-01

    Diffraction of linearly polarized plane electromagnetic waves at the periodically corrugated boundary of vacuum and a linear, homogeneous, uniaxial, dielectric-magnetic medium is formulated as a boundary-value problem and solved using the Rayleigh method. The focus is on situations where the diffracted fields maintain the same polarization state as the s- or p-polarized incident plane wave. Attention is paid to two classes of diffracting media: those with negative definite permittivity and permeability tensors, and those with indefinite permittivity and permeability tensors. For the situations investigated, whereas the dispersion equations in the diffracting medium turn out to be elliptic for the first class of diffracting media, they are hyperbolic for the second class. Examples are reported with the first class of diffracting media of instances when the grating acts either as a positively refracting interface or as a negatively refracting interface. For the second class of diffracting media, hyperbolic dispersion equations imply the possibility of an infinite number of refraction channels.

  20. Diffraction by a grating made of a uniaxial dielectric-magnetic medium exhibiting negative refraction

    International Nuclear Information System (INIS)

    Depine, Ricardo A; Lakhtakia, Akhlesh

    2005-01-01

    Diffraction of linearly polarized plane electromagnetic waves at the periodically corrugated boundary of vacuum and a linear, homogeneous, uniaxial, dielectric-magnetic medium is formulated as a boundary-value problem and solved using the Rayleigh method. The focus is on situations where the diffracted fields maintain the same polarization state as the s- or p-polarized incident plane wave. Attention is paid to two classes of diffracting media: those with negative definite permittivity and permeability tensors, and those with indefinite permittivity and permeability tensors. For the situations investigated, whereas the dispersion equations in the diffracting medium turn out to be elliptic for the first class of diffracting media, they are hyperbolic for the second class. Examples are reported with the first class of diffracting media of instances when the grating acts either as a positively refracting interface or as a negatively refracting interface. For the second class of diffracting media, hyperbolic dispersion equations imply the possibility of an infinite number of refraction channels

  1. Nuclear polarization and neutrons

    International Nuclear Information System (INIS)

    Glaettli, H.

    1985-01-01

    Different possibilities for the use of polarized nuclei in thermal neutron scattering on condensed matter are reviewed. Highly polarized nuclei are the starting point for studying dipolar magnetic order. Systematic measurement of spin-dependent scattering lengths is possible on samples with polarized nuclei. Highly polarized hydrogen should help to unravel complicated structures in chemistry and biology. The use of polarized proton targets as an energy-independent neutron polarizer in the thermal and epithermal region should be considered afresh. (author)

  2. Neutron diffraction studies of glasses

    International Nuclear Information System (INIS)

    Wright, A.C.

    1987-01-01

    A survey is given of the application of neutron diffraction to structural studies of oxide and halide glasses. As with crystalline materials, neutron and X-ray diffraction are the major structural probes for glasses and other amorphous solids, particularly in respect of intermediate range order. The glasses discussed mostly have structures which are dominated by a network in which the bonding is predominantly covalent. The examples discussed demonstrate the power of the neutron diffraction technique in the investigation of the structures of inorganic glasses. The best modern diffraction experiments are capable of providing accurate data with high real space resolution, which if used correctly, are an extremely fine filter for the various structural models proposed in the literature. 42 refs

  3. Diffraction at a Straight Edge

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 5. Diffraction at a Straight Edge: A Gem from Sommerfeld's Work in Classical Physics. Rajaram Nityananda. General Article Volume 20 Issue 5 May 2015 pp 389-400 ...

  4. Neutron Powder Diffraction in Sweden

    International Nuclear Information System (INIS)

    Tellgren, R.

    1986-01-01

    Neutron powder diffraction in Sweden has developed around the research reactor R2 in Studsvik. The article describes this facility and presents a historical review of research results obtained. It also gives some ideas of plans for future development

  5. Tomography with energy dispersive diffraction

    Science.gov (United States)

    Stock, S. R.; Okasinski, J. S.; Woods, R.; Baldwin, J.; Madden, T.; Quaranta, O.; Rumaiz, A.; Kuczewski, T.; Mead, J.; Krings, T.; Siddons, P.; Miceli, A.; Almer, J. D.

    2017-09-01

    X-ray diffraction can be used as the signal for tomographic reconstruction and provides a cross-sectional map of the crystallographic phases and related quantities. Diffraction tomography has been developed over the last decade using monochromatic x-radiation and an area detector. This paper reports tomographic reconstruction with polychromatic radiation and an energy sensitive detector array. The energy dispersive diffraction (EDD) geometry, the instrumentation and the reconstruction process are described and related to the expected resolution. Results of EDD tomography are presented for two samples containing hydroxyapatite (hAp). The first is a 3D-printed sample with an elliptical crosssection and contains synthetic hAp. The second is a human second metacarpal bone from the Roman-era cemetery at Ancaster, UK and contains bio-hAp which may have been altered by diagenesis. Reconstructions with different diffraction peaks are compared. Prospects for future EDD tomography are also discussed.

  6. Diffraction at a Straight Edge

    Indian Academy of Sciences (India)

    IAS Admin

    teaching and understanding physics. ... and mathematical footing, using electromagnetic theory and the proper ... this article, we will use the word diffraction to cover all experiments ..... PES Institute of Technology. Campus ... communication!)

  7. Experimental studies of diffractive phenomena

    International Nuclear Information System (INIS)

    Cool, R.L.

    1984-01-01

    The coherent inelastic scattering process, usually called inclusive diffraction dissociation, is discussed. Topics include: t and M/sub x/ dependence, factorization, finite mass sum rule and charged particle multiplicities. 6 references, 14 figures

  8. Interrogation of orbital structure by elliptically polarized intense femtosecond laser pulses

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We solve the three-dimensional time-dependent Schrödinger equation and present investigations of the imprint of the orbital angular node in photoelectron momentum distributions of an aligned atomic p-type orbital following ionization by an intense elliptically polarized laser pulse of femtosecond...

  9. Transparent thin film polarizing and optical control systems

    Directory of Open Access Journals (Sweden)

    Nelson V. Tabiryan

    2011-06-01

    Full Text Available We show that a diffractive waveplate can be combined with a phase retardation film for fully converting light of arbitrary polarization state into a polarized light. Incorporating a photonic bandgap layer into a system of such polarizers that unify different polarization states in the input light into a single polarization state at its output, rather than absorbing or reflecting half of it, we developed and demonstrated a polarization-independent optical controller capable of switching between transmittive and reflective states. The transition between those states is smoothly controlled with low-voltage and low-power sources. Using versatile fabrication methods, this “universally polarizing optical controller” can be integrated into a thin package compatible with a variety of display, spatial light modulation, optical communication, imaging and other photonics systems.

  10. Diffractive production and hadron structure

    International Nuclear Information System (INIS)

    Nussinov, S.; Szwed, J.

    1979-01-01

    Analysis of diffractive production on nuclei implied cross sections of the diffractively produced system on nucleons which are smaller than the corresponding projectile nucleon cross sections. A natural explanation for this feature is provided in the Good-Walker coherent production formalism. A specific realization of the Good-Walker formalism stated in terms of quarks and connecting electric flux tubes and some ensuing consequences are also discussed briefly. (Auth.)

  11. CONFERENCE: Elastic and diffractive scattering

    Energy Technology Data Exchange (ETDEWEB)

    White, Alan

    1989-09-15

    Elastic scattering, when particles appear to 'bounce' off each other, and the related phenomena of diffractive scattering are currently less fashionable than the study of hard scattering processes. However this could change rapidly if unexpected results from the UA4 experiment at the CERN Collider are confirmed and their implications tested. These questions were highlighted at the third 'Blois Workshop' on Elastic and Diffractive Scattering, held early in May on the Evanston campus of Northwestern University, near Chicago.

  12. Theoretical review of diffractive phenomena

    International Nuclear Information System (INIS)

    Golec-Biernat, K.

    2005-01-01

    We review QCD based descriptions of diffractive deep inelastic scattering emphasising the role of models with parton saturation. These models provide natural explanation of such experimentally observed facts as the constant ratio of σ diff /σ tot as a function of the Bjorken variable x, and Regge factorization of diffractive parton distributions. The Ingelman-Schlein model and the soft color interaction model are also presented

  13. The Diffraction Response Interpolation Method

    DEFF Research Database (Denmark)

    Jespersen, Søren Kragh; Wilhjelm, Jens Erik; Pedersen, Peder C.

    1998-01-01

    Computer modeling of the output voltage in a pulse-echo system is computationally very demanding, particularly whenconsidering reflector surfaces of arbitrary geometry. A new, efficient computational tool, the diffraction response interpolationmethod (DRIM), for modeling of reflectors in a fluid...... medium, is presented. The DRIM is based on the velocity potential impulseresponse method, adapted to pulse-echo applications by the use of acoustical reciprocity. Specifically, the DRIM operates bydividing the reflector surface into planar elements, finding the diffraction response at the corners...

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

    Science.gov (United States)

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

    2012-10-10

    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.

  15. Ultrafast photoelectron spectroscopy of small molecule organic films

    Science.gov (United States)

    Read, Kendall Laine

    As research in the field of ultrafast optics has produced shorter and shorter pulses, at an ever-widening range of frequencies, ultrafast spectroscopy has grown correspondingly. In particular, ultrafast photoelectron spectroscopy allows direct observation of electrons in transient or excited states, regardless of the eventual relaxation mechanisms. High-harmonic conversion of 800nm, femtosecond, Ti:sapphire laser pulses allows excite/probe spectroscopy down into atomic core level states. To this end, an ultrafast, X-UV photoelectron spectroscopic system is described, including design considerations for the high-harmonic generation line, the time of flight detector, and the subsequent data collection electronics. Using a similar experimental setup, I have performed several ultrafast, photoelectron excited state decay studies at the IBM, T. J. Watson Research Center. All of the observed materials were electroluminescent thin film organics, which have applications as the emitter layer in organic light emitting devices. The specific materials discussed are: Alq, BAlq, DPVBi, and Alq doped with DCM or DMQA. Alq:DCM is also known to lase at low photoexcitation thresholds. A detailed understanding of the involved relaxation mechanisms is beneficial to both applications. Using 3.14 eV excite, and 26.7 eV probe, 90 fs laser pulses, we have observed the lowest unoccupied molecular orbital (LUMO) decay rate over the first 200 picoseconds. During this time, diffusion is insignificant, and all dynamics occur in the absence of electron transport. With excitation intensities in the range of 100μJ/cm2, we have modeled the Alq, BAlq, and DPVBi decays via bimolecular singlet-singlet annihilation. At similar excitations, we have modeled the Alq:DCM decay via Förster transfer, stimulated emission, and excimeric formation. Furthermore, the Alq:DCM occupied to unoccupied molecular orbital energy gap was seen to shrink as a function of excite-to-probe delay, in accordance with the

  16. Attosecond photoelectron spectroscopy of electron transport in solids

    International Nuclear Information System (INIS)

    Magerl, Elisabeth

    2011-01-01

    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

  17. 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

  18. Spin-resolved photoelectron spectroscopy of Mn{sub 6}Cr single-molecule-magnets and of manganese compounds as reference layers

    Energy Technology Data Exchange (ETDEWEB)

    Helmstedt, Andreas; Gryzia, Aaron; Dohmeier, Niklas; Mueller, Norbert; Brechling, Armin; Sacher, Marc; Heinzmann, Ulrich [Faculty of Physics, Bielefeld University (Germany); Hoeke, Veronika; Glaser, Thorsten [Faculty of Chemistry, Bielefeld University (Germany); Fonin, Mikhail; Ruediger, Ulrich [Department of Physics, University of Konstanz (Germany); Neumann, Manfred [Department of Physics, Osnabrueck University (Germany)

    2011-07-01

    The properties of the manganese-based single-molecule-magnet (SMM) Mn{sub 6}Cr are studied. This molecule exhibits a large spin ground state of S{sub T}=21/2. It contains six manganese centres arranged in two bowl-shaped Mn{sub 3}-triplesalen building blocks linked by a hexacyanochromate. The Mn{sub 6}Cr complex can be isolated with different counterions which compensate for its triply positive charge. The spin polarization of photoelectrons emitted from the manganese centres in Mn{sub 6}Cr SMM after resonant excitation with circularly polarized synchrotron radiation has been measured at selected energies corresponding to the prominent Mn L{sub 3}VV and L{sub 3}M{sub 2,3}V Auger peaks. Spin-resolved photoelectron spectra of the reference substances MnO, Mn{sub 2}O{sub 3} and Mn(II)acetate recorded after resonant excitation at the Mn-L{sub 3}-edge around 640eV are presented as well. The spin polarization value obtained from MnO at room temperature in the paramagnetic state is compared to XMCD measurements of Mn(II)-compounds at 5K and a magnetic field of 5T.

  19. Neutron polarization in polarized 3He targets

    International Nuclear Information System (INIS)

    Friar, J.L.; Gibson, B.F.; Payne, G.L.; Bernstein, A.M.; Chupp, T.E.

    1990-01-01

    Simple formulas for the neutron and proton polarizations in polarized 3 He targets are derived assuming (1) quasielastic final states; (2) no final-state interactions; (3) no meson-exchange currents; (4) large momentum transfers; (5) factorizability of 3 He SU(4) response-function components. Numerical results from a wide variety of bound-state solutions of the Faddeev equations are presented. It is found that this simple model predicts the polarization of neutrons in a fully polarized 3 He target to be 87%, while protons should have a slight residual polarization of -2.7%. Numerical studies show that this model works very well for quasielastic electron scattering

  20. On the inversion problem of the plasma line intensity measurements in terms of photoelectron fluxes

    International Nuclear Information System (INIS)

    Lejeune, G.

    1979-01-01

    Assuming that the unidimensional distribution function of the photoelectron flux can be determined from plasma line intensity measurement, it is shown that the photoelectron flux distribution is not uniquely determined if additional hypotheses are not made. The limitations of the inversion procedure are shown: in particular, plasma line measurements cannot allow the determination of more than the first two Legendre components of the photoelectron flux. Experimental procedures for this determination are finally reviewed. (author)

  1. Measurement of the Photoelectron Detection Efficiency of the HPD Anode

    CERN Document Server

    Carson, L; Soler, P

    2009-01-01

    This paper reports on measurements carried out on the Hybrid Photon Detectors (HPDs) of the LHCb RICH detectors. The purpose of these tests is to determine the photoelectron detection efficiency $\\eta$ of the HPD anode. Knowledge of $\\eta$ is required for an accurate simulation of the RICH detectors. It is found that this efficiency is $(93.3\\pm0.7)\\%$ for a 50 ns digital readout window, and $(87.9\\pm1.4)\\%$ for a 25 ns digital readout window. The 25 ns result exceeds the LHCb-RICH requirement of 85\\%, and is in agreement both with direct $\\eta$ measurements using preseries HPDs, and with indirect measurements from testbeams using preseries and production HPDs.

  2. Theory of photoelectron spectroscopy for organic molecules and their crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fujikawa, Takashi, E-mail: tfujikawa@faculty.chiba-u.jp; Niki, Kaori; Sakuma, Hiroto

    2015-10-01

    Highlights: • Some specific features in photoemission theory from organic solids are reviewed. • Extrinsic and intrinsic effects are discussed. • Photoemission from extended levels is compared with that from core levels. • First principle many-body theories are discussed on the basis of nonequilibrium Green's functions. - Abstract: In this short review we discuss recent progress in photoemission theory for organic molecules and their crystals. We discuss some important features in Keldysh Green's function theory for the photoemission. We briefly discuss many-body aspects in photoemission from core and extended levels. In particular phonon effects are investigated in more detail since organic solids are typically soft where electron–phonon interaction is important. Debye–Waller factor suppresses the interference effects of photoelectron waves which makes ARPES analyses useless, particularly in high energy region.

  3. Negative ion photoelectron spectroscopy of SeO-

    International Nuclear Information System (INIS)

    Coe, J.V.; Snodgrass, J.T.; Freidhoff, C.B.; McHugh, K.M.; Bowen, K.H.

    1985-01-01

    Negative ion photoelectron spectroscopy (NIPES) involves a kinetic energy analysis of electrons which are photodetached when a mass selected beam of negative ions is crossed with a fixed frequency laser beam. The photodetachment spectra of SeO - displays transitions from the X 2 PI state of SeO - to both the X 3 Σ - and a 1 Δ states of SeO. The singlet-triplet splitting of SeO is readily observable since selection rules regarding spin do not apply in the bound to free state process of photodetachment. The electron affinity of SeO and the negative ion potential parameters of SeO - have been determined

  4. Selectivity in Ketenimine Cycloadditions. Photoelectron Hel Spectra of Ketenimines

    Science.gov (United States)

    Bernardi, Fernando; Bottoni, Andrea; Ballaglia, Arturo; Distefano, Giuseppe; Dondoni, Alessandro

    1980-05-01

    The first few bands in the photoelectron (Hel) spectra of ketenimines R1R2C-C=NR3(R1,R2=H, CH3, C5H6, CH2=CH; R3=alkyl or aryl group) are assigned to the corresponding molecular orbitals. The assignment is based on SCF-MO calculations made at three different levels (CNDO/2, ab-initio STO-3C and 4-31G) coupled with perturbational molecular orbital analyses. The π-orbitals of the unsaturated substituents are found to interact with one of the two perpendicular π-electron systems of the>C=C=N- residue, the critical factor being the position of attack of the substituent. The relevance of these results on the site selectivity observed in cycloaddition reactions of these species is discussed.

  5. DESIGN OF A DC/RF PHOTOELECTRON GUN

    International Nuclear Information System (INIS)

    YU, D.; NEWSHAM, Y.; SMIRONOV, A.; YU, J.; SMEDLEY, J.; SRINIVASAN RAU, T.; LEWELLEN, J.; ZHOLENTS, A.

    2003-01-01

    An integrated dc/rf photoelectron gun produces a low-emittance beam by first rapidly accelerating electrons at a high gradient during a short (∼1 ns), high-voltage pulse, and then injecting the electrons into an rf cavity for subsequent acceleration. Simulations show that significant improvement of the emittance appears when a high field (∼ 0.5-1 GV/m) is applied to the cathode surface. An adjustable dc gap ((le) 1 mm) which can be integrated with an rf cavity is designed for initial testing at the Injector Test Stand at Argonne National Laboratory using an existing 70-kV pulse generator. Plans for additional experiments of an integrated dc/rf gun with a 250-kV pulse generator are being made

  6. Photoelectron emission from metal surfaces by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Faraggi, M. N.; Gravielle, M. S.; Silkin, V. M.

    2006-01-01

    Electron emission from metal surfaces produced by short laser pulses is studied within the framework of the distorted-wave formulation. The proposed approach, named surface-Volkov (SV) approximation, makes use of the band-structure based (BSB) model and the Volkov phase to describe the interaction of the emitted electron with the surface and the external electric field, respectively. The BSB model provides a realistic representation of the surface, based on a model potential that includes the main features of the surface band structure. The SV method is applied to evaluate the photoelectron emission from the valence band of Al(111). Angular and energy distributions are investigated for different parameters of the laser pulse, keeping in all cases the carrier frequency larger than the plasmon one

  7. Slow photoelectron imaging spectroscopy of CCO- and CCS-.

    Science.gov (United States)

    Garand, Etienne; Yacovitch, Tara I; Neumark, Daniel M

    2008-08-21

    High-resolution photodetachment spectra of CCO(-) and CCS(-) using slow photoelectron velocity-map imaging spectroscopy are reported. Well-resolved transitions to the neutral X (3)Sigma(-), a (1)Delta, b (1)Sigma(+), and A (3)Pi states are seen for both species. The electron affinities of CCO and CCS are determined to be 2.3107+/-0.0006 and 2.7475+/-0.0006 eV, respectively, and precise term energies for the a (1)Delta, b (1)Sigma(+), and A (3)Pi excited states are also determined. The two low-lying singlet states of CCS are observed for the first time, as are several vibronic transitions within the four bands. Analysis of hot bands finds the spin-orbit orbit splitting in the X (2)Pi ground state of CCO(-) and CCS(-) to be 61 and 195 cm(-1), respectively.

  8. Photoelectron imaging, probe of the dynamics: from atoms... to clusters

    International Nuclear Information System (INIS)

    Lepine, F.

    2003-06-01

    This thesis concerns the study of the deexcitation of clusters and atoms by photoelectron imaging. The first part is dedicated to thermionic emission of a finite size system. A 3-dimensional imaging setup allows us to measure the time evolution of the kinetic energy spectrum of electrons emitted from different clusters (W n - , C n - , C 60 ). Then we have a direct access to the fundamental quantities which characterize this statistical emission: the temperature of the finite heat bath and the decay rate. The second part concerns the ionization of atomic Rydberg states placed in a static electric field. We performed the first experiment of photoionization microscopy which allows us to obtain a picture which is the macroscopic projection of the electronic wave function. Then we have access to the detail of the photoionization and particularly to the quantum properties of the electron usually confined at the atomic scale. (author)

  9. X-ray photoelectron spectra of γ-irradiated perfluorobenzene

    International Nuclear Information System (INIS)

    Sunder, S.; Sagert, N.H.; Wood, D.D.; Miller, N.H.

    1990-01-01

    The effect of γ-radiolysis on perfluorobenzene (PFB) was investigated using low-temperature X-ray photoelectron spectroscopy (XPS). PFB was irradiated in fluorine-passivated nickel cells using Co 60 γ-rays in an Atomic Energy of Canada Limited Gammacell at a dose rate of about 2.6 Gy·s -1 and for a total dose of about 50 kGy. The γ-radiolysis of PFB not only results in cross-linkage but also in the formation of saturated carbon centers in the PFB, as indicated by the presence of CF 2 and CF 3 groups. The relative abundance of CF, CF 2 and CF 3 groups, in the irradiated PFB, was estimated to be about 86, 9 and 5%, respectively

  10. Study of transition metal oxides by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Rao, C.N.R.; Sarma, D.D.; Vasudevan, S.; Hegde, M.S.

    1979-01-01

    Systematics in the X-ray photoelectron spectra (X.p.e.s.) of Ti, V, Cr, Mn and Nb oxides with the metal ion in different oxidation states as well as of related series of mono-, sesqui- and di-oxides of the first row of transition metals have been investigated in detail. Core level binding energies, spin-orbit splittings and exchange splittings are found to exhibit interesting variations with the oxidation state of the metal or the nuclear charge. The 3d binding energies of the monoxides show a proportionality to Goodenough's (R - RC). Other aspects of interest in the study are the satellite structure and final state effects in the X.p.e.s. of the oxides, and identification of different valence states in oxides of the general formulae Mn02n-1 and M304. The nature of changes in the 3d bands of oxides undergoing metal-insulator transitions is also indicated. (author)

  11. Theory of photoelectron spectroscopy for organic molecules and their crystals

    International Nuclear Information System (INIS)

    Fujikawa, Takashi; Niki, Kaori; Sakuma, Hiroto

    2015-01-01

    Highlights: • Some specific features in photoemission theory from organic solids are reviewed. • Extrinsic and intrinsic effects are discussed. • Photoemission from extended levels is compared with that from core levels. • First principle many-body theories are discussed on the basis of nonequilibrium Green's functions. - Abstract: In this short review we discuss recent progress in photoemission theory for organic molecules and their crystals. We discuss some important features in Keldysh Green's function theory for the photoemission. We briefly discuss many-body aspects in photoemission from core and extended levels. In particular phonon effects are investigated in more detail since organic solids are typically soft where electron–phonon interaction is important. Debye–Waller factor suppresses the interference effects of photoelectron waves which makes ARPES analyses useless, particularly in high energy region.

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

    International Nuclear Information System (INIS)

    Wang, Lai-Sheng; Reutt-Robey, J.E.; Niu, B.; Lee, Y.T.; Shirley, D.A.

    1989-07-01

    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, As 2 , As 4 , and ZnCl 2 are shown to demonstrate the performance of the new source. 25 refs., 8 figs., 1 tab

  13. Introduction to x-ray photoelectron spectroscopy (XPS)

    International Nuclear Information System (INIS)

    Liesegang, J.; Pigram, P.J.

    1999-01-01

    Full text: XPS is one of several important surface analytical tools. Developed in Sweden in the 1960s, it was originally named by Kai Siegbahn as Electron Spectroscopy for Chemical Analysis or ESCA; and although it is the best method for non-invasively determining the elemental composition of the first 10 nm of any surface, modern XPS systems are capable of much more than elemental chemical analysis. High resolution photoelectron energy analysis (c. 0.2 eV) now permits easy identification of chemical state as well as concentration; angular variation of detection and depth profiling allow quantitative analysis as a function of depth below a sample surface; energy loss mechanisms may be studied; Auger peaks can be measured in an XPS system; and developments in the area of photoelectron imaging allow high resolution (c. 7 μm) mapping of the distribution of elements and their chemical states to be determined spatially on non-homogeneous surfaces. The workshop sessions will outline the link between the physics and chemistry of surfaces and the process of photoemission. The presentation will illustrate the features and capabilities of a newly acquired Kratos (UK) Axis Ultra XPS and Imaging System recently installed in the Centre for Materials and Surface Science at La Trobe University, and its capabilities regarding the foregoing issues. The first part of the presentation will outline the basics of XPS and the second part will illustrate its usefulness, and in particular, will illustrate the power of the instrumentation through the presentation of several applications of both fundamental and industrial significance. Copyright (1999) Australian X-ray Analytical Association Inc

  14. Design of a Binary Grating with Subwavelength Features that Acts as a Polarizing Beam Splitter.

    Science.gov (United States)

    Pajewski, L; Borghi, R; Schettini, G; Frezza, F; Santarsiero, M

    2001-11-10

    A binary diffractive optical element, acting as a polarizing beam splitter, is proposed and analyzed. It behaves like a transmissive blazed grating, working on the first or the second diffraction order, depending on the polarization state of the incident radiation. The grating-phase profile required for both polarization states is obtained by means of suitably sized subwavelength groups etched in an isotropic dielectric medium. A rigorous electromagnetic analysis of the grating is presented, and numerical results concerning its performances in terms of diffraction efficiency as well as frequency and angular bandwidths are provided.

  15. Effects of polarization of polar semiconductor on electrical properties of poly(vinylidene fluoride-trifluoroethylene)/ZnO heterostructures

    International Nuclear Information System (INIS)

    Yamada, Hiroaki; Yoshimura, Takeshi; Fujimura, Norifumi

    2015-01-01

    The electrical properties of heterostructures composed of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and ZnO with different crystallographic polarities, i.e., O- and Zn-polar ZnO, were investigated. Distinct differences in the capacitance-voltage and polarization-voltage characteristics between the P(VDF-TrFE)/O- and Zn-polar ZnO were obtained in the depletion regions of ZnO. The band configurations were determined by X-ray photoelectron spectroscopy (XPS) using a synchrotron radiation beam to analyze the differences in the electrical properties of the P(VDF-TrFE)/O- and Zn-polar ZnO. The XPS spectra indicated that the valence band maximum of P(VDF-TrFE) is 2.9 and 2.7 eV higher than Zn- and O-polar ZnO, respectively. Thus, both structures have staggered band configurations with large valence band offsets, and the spontaneous polarization of ZnO is less effective on the band lineup. The electrical properties of the P(VDF-TrFE)/ZnO heterostructures are modulated through carrier generation because of the polarization-mediated interface charges and the staggered band alignments of the P(VDF-TrFE)/ZnO with a large valence band offset

  16. Neutron diffraction and oxide research

    International Nuclear Information System (INIS)

    Hunter, B.; Howard, C.J.; Kennedy, B.J.

    1999-01-01

    Oxide compounds form a large class of interesting materials that have a diverse range of mechanical and electronic properties. This diversity and its commercial implications has had a significant impact on physics research. This is particularly evident in the fields of superconductivity magnetoresistivity and ferroelectricity, where discoveries in the last 15 years have given rise to significant shifts in research activities. Historically, oxides have been studied for many years, but it is only recently that significant effort has been diverted to the study of oxide materials for their application to mechanical and electronic devices. An important property of such materials is the atomic structure, for the determination of which diffraction techniques are ideally suited. Recent examples of structure determinations using neutron diffraction in oxide based systems are high temperature superconductors, where oxygen defects are a key factor. Here, neutron diffraction played a major role in determining the effect of oxygen on the superconducting properties. Similarly, neutron diffraction has enjoyed much success in the determination of the structures of the manganate based colossal magnetoresistive (CMR) materials. In both these cases the structure plays a pivotal role in determining theoretical models of the electronic properties. The neutron scattering group at ANSTO has investigated several oxide systems using neutron powder diffraction. Two such systems are presented in this paper; the zirconia-based materials that are used as engineering materials, and the perovskite-based oxides that include the well known cuprate superconductors and the manganate CMR materials

  17. Polarized electron sources

    International Nuclear Information System (INIS)

    Prepost, R.

    1994-01-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented

  18. Polarized electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Prepost, R. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented.

  19. High-energy particle diffraction

    International Nuclear Information System (INIS)

    Barone, V.; Predazzi, E.

    2002-01-01

    This monograph gives a comprehensive and up-to-date overview of soft and hard diffraction processes in strong interaction physics. The first part covers the general formalism (the optical analogy, the eikonal picture, high-energy kinematics, S-matrix theory) and soft hadron-hadron scattering (including the Regge theory) in a complete and mature presentation. It can be used as a textbook in particle physics classes. The remainder of the book is devoted to the 'new diffraction': the pomeron in QCD, low-x physics, diffractive deep inelastic scattering and related processes, jet production etc. It presents recent results and experimental findings and their phenomenological interpretations. This part addresses graduate students as well as researchers. (orig.)

  20. Diffraction of high energy electrons

    International Nuclear Information System (INIS)

    Bourret, A.

    1981-10-01

    The diffraction of electrons by a crystal is examined to study its structure. As the electron-substance interaction is strong, it must be treated in a dynamic manner. Using the N waves theory and physical optics the base equations giving the wave at the outlet are deduced for a perfect crystal and their equivalence is shown. The more complex case of an imperfect crystal is then envisaged in these two approaches. In both cases, only the diffraction of high energy electrons ( > 50 KeV) are considered since in the diffraction of slow electrons back scattering cannot be ignored. Taking into account an increasingly greater number of beams, through fast calculations computer techniques, enables images to be simulated in very varied conditions. The general use of the Fast Fourier Transform has given a clear cut practical advantage to the multi-layer method [fr

  1. Hard diffraction and rapidity gaps

    International Nuclear Information System (INIS)

    Brandt, A.

    1995-09-01

    The field of hard diffraction, which studies events with a rapidity gap and a hard scattering, has expanded dramatically recently. A review of new results from CDF, D OE, H1 and ZEUS will be given. These results include diffractive jet production, deep-inelastic scattering in large rapidity gap events, rapidity gaps between high transverse energy jets, and a search for diffractive W-boson production. The combination of these results gives new insight into the exchanged object, believed to be the pomeron. The results axe consistent with factorization and with a hard pomeron that contains both quarks and gluons. There is also evidence for the exchange of a strongly interacting color singlet in high momentum transfer (36 2 ) events

  2. Light diffraction through a feather

    Directory of Open Access Journals (Sweden)

    Pérez García, Hugo;

    2012-01-01

    Full Text Available We have used a feather to study light diffraction, in a qualitative as well as in a quantitative manner. Experimental measurement of the separation between the bright spots obtained with a laser pointer allowed the determination of the space between feather's barbs and barbules. The results we have obtained agree satisfactorily with those corresponding to a typical feather. Due to the kind of materials, the related concepts and the experimental results, this activity becomes an excellent didactic resource suitable for studying diffraction, both in introductory undergraduate as well as in secondary school physics courses.

  3. CONFERENCE: Elastic and diffractive scattering

    International Nuclear Information System (INIS)

    White, Alan

    1989-01-01

    Elastic scattering, when particles appear to 'bounce' off each other, and the related phenomena of diffractive scattering are currently less fashionable than the study of hard scattering processes. However this could change rapidly if unexpected results from the UA4 experiment at the CERN Collider are confirmed and their implications tested. These questions were highlighted at the third 'Blois Workshop' on Elastic and Diffractive Scattering, held early in May on the Evanston campus of Northwestern University, near Chicago

  4. Dynamical theory of neutron diffraction

    International Nuclear Information System (INIS)

    Sears, V.F.

    1978-01-01

    We present a review of the dynamical theory of neutron diffraction by macroscopic bodies which provides the theoretical basis for the study of neutron optics. We consider both the theory of dispersion, in which it is shown that the coherent wave in the medium satisfies a macroscopic one-body Schroedinger equation, and the theory of reflection, refraction, and diffraction in which the above equation is solved for a number of special cases of interest. The theory is illustrated with the help of experimental results obtained over the past 10 years by a number of new techniques such as neutron gravity refractometry. Pendelloesung interference, and neutron interferometry. (author)

  5. Diffractive dissociation and new quarks

    International Nuclear Information System (INIS)

    White, A.R.

    1983-04-01

    We argue that the chiral limit of QCD can be identified with the strong (diffractive dissociation) coupling limit of reggeon field theory. Critical Pomeron scaling at high energy must then be directly related to an infra-red fixed-point of massless QCD and so requires a large number of flavors. This gives a direct argument that the emergence of diffraction-peak scaling, KNO scaling etc. at anti p-p colliders are evidence of a substantial quark structure still to be discovered

  6. Photoemission of Bi_{2}Se_{3} with Circularly Polarized Light: Probe of Spin Polarization or Means for Spin Manipulation?

    Directory of Open Access Journals (Sweden)

    J. Sánchez-Barriga

    2014-03-01

    Full Text Available Topological insulators are characterized by Dirac-cone surface states with electron spins locked perpendicular to their linear momenta. Recent theoretical and experimental work implied that this specific spin texture should enable control of photoelectron spins by circularly polarized light. However, these reports questioned the so far accepted interpretation of spin-resolved photoelectron spectroscopy. We solve this puzzle and show that vacuum ultraviolet photons (50–70 eV with linear or circular polarization indeed probe the initial-state spin texture of Bi_{2}Se_{3} while circularly polarized 6-eV low-energy photons flip the electron spins out of plane and reverse their spin polarization, with its sign determined by the light helicity. Our photoemission calculations, taking into account the interplay between the varying probing depth, dipole-selection rules, and spin-dependent scattering effects involving initial and final states, explain these findings and reveal proper conditions for light-induced spin manipulation. Our results pave the way for future applications of topological insulators in optospintronic devices.

  7. 75 FR 63810 - Grant of Authority for Subzone Status; SICK, Inc. (Photo-Electronic Industrial Sensors...

    Science.gov (United States)

    2010-10-18

    ... Status; SICK, Inc. (Photo- Electronic Industrial Sensors); Bloomington, MN Pursuant to its authority... to establish a special- purpose subzone at the photo-electronic industrial sensor manufacturing and... manufacturing and distribution of photo-electronic industrial sensors at the SICK, Inc., facility located in...

  8. Interrogation of orbital structure by elliptically polarized intense femtosecond laser pulses

    International Nuclear Information System (INIS)

    Abu-samha, M.; Madsen, L. B.

    2011-01-01

    We solve the three-dimensional time-dependent Schroedinger equation and present investigations of the imprint of the orbital angular node in photoelectron momentum distributions of an aligned atomic p-type orbital following ionization by an intense elliptically polarized laser pulse of femtosecond duration. We investigate the role of light ellipticity and the alignment angle of the major polarization axis of the external field relative to the probed orbital by studying radial and angular momentum distributions, the latter at a fixed narrow interval of final momenta close to the peak of the photoelectron momentum distribution. In general only the angular distributions carry a clear signature of the orbital symmetry. Our study shows that circular polarization gives the most clear imprints of orbital nodes. These findings are insensitive to pulse duration.

  9. Recording polarization gratings with a standing spiral wave

    Science.gov (United States)

    Vernon, Jonathan P.; Serak, Svetlana V.; Hakobyan, Rafik S.; Aleksanyan, Artur K.; Tondiglia, Vincent P.; White, Timothy J.; Bunning, Timothy J.; Tabiryan, Nelson V.

    2013-11-01

    A scalable and robust methodology for writing cycloidal modulation patterns of optical axis orientation in photosensitive surface alignment layers is demonstrated. Counterpropagating circularly polarized beams, generated by reflection of the input beam from a cholesteric liquid crystal, direct local surface orientation in a photosensitive surface. Purposely introducing a slight angle between the input beam and the photosensitive surface normal introduces a grating period/orientation that is readily controlled and templated. The resulting cycloidal diffractive waveplates offer utility in technologies requiring diffraction over a broad range of angles/wavelengths. This simple methodology of forming polarization gratings offers advantages over conventional fabrication techniques.

  10. Recording polarization gratings with a standing spiral wave

    Energy Technology Data Exchange (ETDEWEB)

    Vernon, Jonathan P.; Tondiglia, Vincent P.; White, Timothy J.; Bunning, Timothy J. [Air Force Research Laboratory, Materials and Manufacturing Directorate, 3005 Hobson Way, Suite 1, Wright-Patterson Air Force Base, Ohio 45433 (United States); Serak, Svetlana V.; Hakobyan, Rafik S.; Aleksanyan, Artur K.; Tabiryan, Nelson V., E-mail: nelson@beamco.com [BEAM Engineering for Advanced Measurements Company, 809 South Orlando Avenue, Suite I, Winter Park, Florida 32789 (United States)

    2013-11-11

    A scalable and robust methodology for writing cycloidal modulation patterns of optical axis orientation in photosensitive surface alignment layers is demonstrated. Counterpropagating circularly polarized beams, generated by reflection of the input beam from a cholesteric liquid crystal, direct local surface orientation in a photosensitive surface. Purposely introducing a slight angle between the input beam and the photosensitive surface normal introduces a grating period/orientation that is readily controlled and templated. The resulting cycloidal diffractive waveplates offer utility in technologies requiring diffraction over a broad range of angles/wavelengths. This simple methodology of forming polarization gratings offers advantages over conventional fabrication techniques.

  11. Recording polarization gratings with a standing spiral wave

    International Nuclear Information System (INIS)

    Vernon, Jonathan P.; Tondiglia, Vincent P.; White, Timothy J.; Bunning, Timothy J.; Serak, Svetlana V.; Hakobyan, Rafik S.; Aleksanyan, Artur K.; Tabiryan, Nelson V.

    2013-01-01

    A scalable and robust methodology for writing cycloidal modulation patterns of optical axis orientation in photosensitive surface alignment layers is demonstrated. Counterpropagating circularly polarized beams, generated by reflection of the input beam from a cholesteric liquid crystal, direct local surface orientation in a photosensitive surface. Purposely introducing a slight angle between the input beam and the photosensitive surface normal introduces a grating period/orientation that is readily controlled and templated. The resulting cycloidal diffractive waveplates offer utility in technologies requiring diffraction over a broad range of angles/wavelengths. This simple methodology of forming polarization gratings offers advantages over conventional fabrication techniques

  12. On the polarization mixing of X-rays

    International Nuclear Information System (INIS)

    Ohkawa, T.; Hashimoto, H.

    1984-01-01

    Relativistic quantum field theory is applied to discuss the process of interference of white X-rays and the mechanism of rotation of the polarization of X-rays in crystals. A two-photon state is studied theoretically for analyzing the mechanism of the polarization mixing. Diffracted X-ray photons are produced by two successive stages of interaction between incident X-rays and electrons in a crystal. A dispersion relation of diffracted X-rays similar to Laue's dynamic theory is shown by use of the S-matrix. A dynamical structure factor is defined on the base of Dirac's γ-matrix. (author)

  13. Polarized targets and beams

    International Nuclear Information System (INIS)

    Meyer, W.

    1985-01-01

    First the experimental situation of the single-pion photoproduction and the photodisintegration of the deuteron is briefly discussed. Then a description of the Bonn polarization facilities is given. The point of main effort is put on the polarized target which plays a vital role in the program. A facility for photon induced double polarization experiments at ELSA will be presented in section 4. Properties of a tensor polarized deuteron target are discussed in section 5. The development in the field of polarized targets, especially on new target materials, enables a new generation of polarized target experiments with (polarized) electrons. Some comments on the use of a polarized target in combination with electron beams will be discussed in section 6. Electron deuteron scattering from a tensor polarized deuteron target is considered and compared with other experimental possibilities. (orig./HSI)

  14. CMS results on soft diffraction

    CERN Document Server

    INSPIRE-00086121

    2013-01-01

    We present measurements of soft single- and double-diffractive cross sections, as well as of forward rapidity gap cross sections at 7 TeV at the LHC, and compare the results to other measurements and to theoretical predictions implemented in various Monte Carlo simulations.

  15. LEED (Low Energy Electron Diffraction)

    International Nuclear Information System (INIS)

    Aberdam, M.

    1973-01-01

    The various types of systems studied by LEED, and for which the geometry of diffraction patterns is exploited, are reviewed, intensity profiles being another source of information. Two representative approaches of the scattering phenomenon are examined; the band structure theory and the T matrix approach [fr

  16. A QCD analysis of ZEUS diffractive data

    Energy Technology Data Exchange (ETDEWEB)

    Chekanov, S.; Derrick, M.; Magill, S. [Argonne National Laboratory, Argonne, IL (US)] (and others)

    2009-11-15

    ZEUS inclusive diffractive cross-section measurements have been used in a DGLAP next-to-leading-order QCD analysis to extract the diffractive parton distribution functions. Data on diffractive dijet production in deep inelastic scattering have also been included to constrain the gluon density. Predictions based on the extracted parton densities are compared to diffractive charm and dijet photoproduction data. (orig.)

  17. A QCD analysis of ZEUS diffractive data

    International Nuclear Information System (INIS)

    Chekanov, S.; Derrick, M.; Magill, S.

    2009-11-01

    ZEUS inclusive diffractive cross-section measurements have been used in a DGLAP next-to-leading-order QCD analysis to extract the diffractive parton distribution functions. Data on diffractive dijet production in deep inelastic scattering have also been included to constrain the gluon density. Predictions based on the extracted parton densities are compared to diffractive charm and dijet photoproduction data. (orig.)

  18. Electro-optic diffraction grating tuned laser

    International Nuclear Information System (INIS)

    Hughes, R.S.

    1975-01-01

    An electro-optic diffraction grating tuned laser comprising a laser medium, output mirror, retro-reflective grating and an electro-optic diffraction grating beam deflector positioned between the laser medium and the reflective diffraction grating is described. An optional angle multiplier may be used between the electro-optic diffraction grating and the reflective grating. (auth)

  19. Polarization effects in above-threshold ionization with a mid-infrared strong laser field

    Science.gov (United States)

    Kang, Hui-Peng; Xu, Song-Po; Wang, Yan-Lan; Yu, Shao-Gang; Zhao, Xiao-Yun; Hao, Xiao-Lei; Lai, Xuan-Yang; Pfeifer, Thomas; Liu, Xiao-Jun; Chen, Jing; Cheng, Ya; Xu, Zhi-Zhan

    2018-05-01

    Using a semiclassical approach, we theoretically study the above-threshold ionization of magnesium by intense, mid-infrared laser pulses. The formation of low-energy structures in the photoelectron spectrum is found to be enhanced by comparing with a calculation based on the single-active electron approximation. By performing electron trajectory and recollision-time distribution analysis, we demonstrate that this phenomenon is due to the laser-induced ionic core polarization effects on the recolliding electrons. We also show that the polarization effects should be experimentally detectable. Our finding provides new insight into ultrafast control of strong-field photoionization and imaging of polar molecules.

  20. Conical diffraction as a versatile building block to implement new imaging modalities for superresolution in fluorescence microscopy

    Science.gov (United States)

    Fallet, Clément; Caron, Julien; Oddos, Stephane; Tinevez, Jean-Yves; Moisan, Lionel; Sirat, Gabriel Y.; Braitbart, Philippe O.; Shorte, Spencer L.

    2014-08-01

    We present a new technology for super-resolution fluorescence imaging, based on conical diffraction. Conical diffraction is a linear, singular phenomenon taking place when a polarized beam is diffracted through a biaxial crystal. The illumination patterns generated by conical diffraction are more compact than the classical Gaussian beam; we use them to generate a super-resolution imaging modality. Conical Diffraction Microscopy (CODIM) resolution enhancement can be achieved with any type of objective on any kind of sample preparation and standard fluorophores. Conical diffraction can be used in multiple fashion to create new and disruptive technologies for super-resolution microscopy. This paper will focus on the first one that has been implemented and give a glimpse at what the future of microscopy using conical diffraction could be.

  1. Angular distributions of photoelectrons from free Na clusters

    International Nuclear Information System (INIS)

    Wopperer, P.; Dinh, P. M.; Faber, B.; Reinhard, P.-G.; Suraud, E.

    2010-01-01

    We explore, from a theoretical perspective, photoelectron angular distributions (PADs) of the Na clusters Na 8 , Na 10 , Na 12 , Na 18 , Na 3 + , Na 11 + , Na 13 + , and Na 19 + . The basis of the description is the time-dependent local-density approximation (TDLDA), augmented by a self-interaction correction (SIC) to describe ionization properties correctly. The scheme is solved on a numerical grid in coordinate space with absorbing bounds. We assume for each cluster system an isotropic ensemble of free clusters and develop for the case of one-photon emission analytical formulas for computing the orientation-averaged PAD on the basis of a few TDLDA-SIC calculations for properly chosen reference orientations. It turns out that all the information in the averaged PAD is contained in one anisotropy parameter. We find that this parameter varies very little with system size, but as a whole is crucially influenced by the detailed ionic structure. We also make comparisons with direct orientation averaging and consider one example reaching outside the perturbative regime.

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

    International Nuclear Information System (INIS)

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

    1988-11-01

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

  3. Core level photoelectron spectroscopy probed heterogeneous xenon/neon clusters

    International Nuclear Information System (INIS)

    Pokapanich, Wandared; Björneholm, Olle; Öhrwall, Gunnar; Tchaplyguine, Maxim

    2017-01-01

    Binary rare gas clusters; xenon and neon which have a significant contrariety between sizes, produced by a co-expansion set up and have been studied using synchrotron radiation based x-ray photoelectron spectroscopy. Concentration ratios of the heterogeneous clusters; 1%, 3%, 5% and 10% were controlled. The core level spectra were used to determine structure of the mixed cluster and analyzed by considering screening mechanisms. Furthermore, electron binding energy shift calculations demonstrated cluster aggregation models which may occur in such process. The results showed that in the case of low mixing ratios of 3% and 5% of xenon in neon, the geometric structures exhibit xenon in the center and xenon/neon interfaced in the outer shells. However, neon cluster vanished when the concentration of xenon was increased to 10%. - Highlights: • Co-expansion setup is suitable for producing binary Xe/Ne clusters. • Appropriate temperature, pressure, and mixing ratios should be strictly controlled. • Low mixing ratio, Xe formed in the core and Xe/Ne interfacing in the outer shell. • High mixing ratio, only pure Xe clusters were detected.

  4. Depth-profiling using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Pijolat, M.; Hollinger, G.

    1980-12-01

    The possibilities of X-ray photoelectron spectroscopy (or ESCA) for depth-profiling into shallow depths (approximately 10-100 A) have been studied. The method of ion-sputtering removal has first been investigated in order to improve its depth-resolution (approximately 50-150 A). A procedure which eliminates the effects due to the resolution function of the instrumental probe (analysed depth approximately 50 A) has been settled; but it is not yet sufficient, and the sputter - broadening due to the ion-induced damages must be taken into account (broadening function approximately 50 A for approximately 150 A removal). Because of serious difficulties in estimating the broadening function an alternative is to develop non destructive methods, so a new method based on the dependence of the analysed depth with the electron emission angle is presented. The extraction of the concentration profile from angular distribution experiments is achieved, in the framework of a flat-layer model, by minimizing the difference between theoretical and experimental relative intensities. The applicability and limitations of the method are discussed on the basis of computer simulation results. The depth probed is of the order of 3 lambda (lambda being the value of the inelastic mean free path, typically 10-20 A) and the depth-resolution is of the order of lambda/3 [fr

  5. X-ray-excited Auger and photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Weightman, P.

    1982-01-01

    This article reviews developments in the understanding of x-ray-excited Auger and photoelectron spectra in the light of theoretical developments in atomic, molecular and solid-state physics. After reviewing progress in XPS and AES separately emphasis is placed on the inter-relationship between the two fields: Auger rates, for example, are the dominant contribution to core-level XPS linewidths and by combining XPS and AES it is possible to deduce information about Coster-Kronig processes which are difficult to study directly. An account is given of how the combination of measurements of environmentally dependent shifts in XPS and AES energies allows one to isolate initial- and final-state contributions which can then be related to the results of other experimental techniques. There is a brief discussion of many-electron effects and a discussion of how the combination of XPS and AES spectra involving valence levels enables the effects of hole-state localisation to be studied. (author)

  6. Widespread spin polarization effects in photoemission from topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, C.; Chen, Y. L.; Fedorov, A. V.; Analytis, J. G.; Rotundu, C. R.; Schmid, A. K.; Denlinger, J. D.; Chuang, Y.-D.; Lee, D.-H.; Fisher, I. R.; Birgeneau, R. J.; Shen, Z.-X.; Hussain, Z.; Lanzara, A.

    2011-06-22

    High-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES) was performed on the three-dimensional topological insulator Bi{sub 2}Se{sub 3} using a recently developed high-efficiency spectrometer. The topological surface state's helical spin structure is observed, in agreement with theoretical prediction. Spin textures of both chiralities, at energies above and below the Dirac point, are observed, and the spin structure is found to persist at room temperature. The measurements reveal additional unexpected spin polarization effects, which also originate from the spin-orbit interaction, but are well differentiated from topological physics by contrasting momentum and photon energy and polarization dependencies. These observations demonstrate significant deviations of photoelectron and quasiparticle spin polarizations. Our findings illustrate the inherent complexity of spin-resolved ARPES and demonstrate key considerations for interpreting experimental results.

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

    Science.gov (United States)

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

    2014-03-11

    Broken-symmetry density functional theory (BS-DFT) calculations are assessed for redox energetics [Cu(SCH 3 ) 2 ] 1-/0 , [Cu(NCS) 2 ] 1-/0 , [FeCl 4 ] 1-/0 , and [Fe(SCH 3 ) 4 ] 1-/0 against vertical detachment energies (VDE) from valence photoelectron spectroscopy (PES), as a prelude to studies of metalloprotein analogs. The M06 and B3LYP hybrid functionals give VDE that agree with the PES VDE for the Fe complexes, but both underestimate it by ∼400 meV for the Cu complexes; other hybrid functionals give VDEs that are an increasing function of the amount of Hartree-Fock (HF) exchange and so cannot show good agreement for both Cu and Fe complexes. Range-separated (RS) functionals appear to give a better distribution of HF exchange since the negative HOMO energy is approximately equal to the VDEs but also give VDEs dependent on the amount of HF exchange, sometimes leading to ground states with incorrect electron configurations; the LRC- ω PBEh functional reduced to 10% HF exchange at short-range give somewhat better values for both, although still ∼150 meV too low for the Cu complexes and ∼50 meV too high for the Fe complexes. Overall, the results indicate that while HF exchange compensates for self-interaction error in DFT calculations of both Cu and Fe complexes, too much may lead to more sensitivity to nondynamical correlation in the spin-polarized Fe complexes.

  8. Exploring the aqueous vertical ionization of organic molecules by molecular simulation and liquid microjet photoelectron spectroscopy.

    Science.gov (United States)

    Tentscher, Peter R; Seidel, Robert; Winter, Bernd; Guerard, Jennifer J; Arey, J Samuel

    2015-01-08

    To study the influence of aqueous solvent on the electronic energy levels of dissolved organic molecules, we conducted liquid microjet photoelectron spectroscopy (PES) measurements of the aqueous vertical ionization energies (VIEaq) of aniline (7.49 eV), veratrole alcohol (7.68 eV), and imidazole (8.51 eV). We also reanalyzed previously reported experimental PES data for phenol, phenolate, thymidine, and protonated imidazolium cation. We then simulated PE spectra by means of QM/MM molecular dynamics and EOM-IP-CCSD calculations with effective fragment potentials, used to describe the aqueous vertical ionization energies for six molecules, including aniline, phenol, veratrole alcohol, imidazole, methoxybenzene, and dimethylsulfide. Experimental and computational data enable us to decompose the VIEaq into elementary processes. For neutral compounds, the shift in VIE upon solvation, ΔVIEaq, was found to range from ≈-0.5 to -0.91 eV. The ΔVIEaq was further explained in terms of the influence of deforming the gas phase solute into its solution phase conformation, the influence of solute hydrogen-bond donor and acceptor interactions with proximate solvent molecules, and the polarization of about 3000 outerlying solvent molecules. Among the neutral compounds, variability in ΔVIEaq appeared largely controlled by differences in solute-solvent hydrogen-bonding interactions. Detailed computational analysis of the flexible molecule veratrole alcohol reveals that the VIE is strongly dependent on molecular conformation in both gas and aqueous phases. Finally, aqueous reorganization energies of the oxidation half-cell ionization reaction were determined from experimental data or estimated from simulation for the six compounds aniline, phenol, phenolate, veratrole alcohol, dimethylsulfide, and methoxybenzene, revealing a surprising constancy of 2.06 to 2.35 eV.

  9. Digital diffractive optics: Have diffractive optics entered mainstream industry yet?

    Science.gov (United States)

    Kress, Bernard; Hejmadi, Vic

    2010-05-01

    When a new technology is integrated into industry commodity products and consumer electronic devices, and sold worldwide in retail stores, it is usually understood that this technology has then entered the realm of mainstream technology and therefore mainstream industry. Such a leap however does not come cheap, as it has a double edge sword effect: first it becomes democratized and thus massively developed by numerous companies for various applications, but also it becomes a commodity, and thus gets under tremendous pressure to cut down its production and integration costs while not sacrificing to performance. We will show, based on numerous examples extracted from recent industry history, that the field of Diffractive Optics is about to undergo such a major transformation. Such a move has many impacts on all facets of digital diffractive optics technology, from the optical design houses to the micro-optics foundries (for both mastering and volume replication), to the final product integrators or contract manufacturers. The main causes of such a transformation are, as they have been for many other technologies in industry, successive technological bubbles which have carried and lifted up diffractive optics technology within the last decades. These various technological bubbles have been triggered either by real industry needs or by virtual investment hype. Both of these causes will be discussed in the paper. The adjective ""digital"" in "digital diffractive optics" does not refer only, as it is done in digital electronics, to the digital functionality of the element (digital signal processing), but rather to the digital way they are designed (by a digital computer) and fabricated (as wafer level optics using digital masking techniques). However, we can still trace a very strong similarity between the emergence of micro-electronics from analog electronics half a century ago, and the emergence of digital optics from conventional optics today.

  10. MAX: Development of a Laue diffraction lens for nuclear astrophysics

    International Nuclear Information System (INIS)

    Barriere, N.; Ballmoos, P. von; Skinner, G.; Smither, B.; Bastie, P.; Hinglais, E.; Abrosimov, N.; Alvarez, J.M.; Andersen, K.; Courtois, P.; Halloin, H.; Harris, M.; Isern, J.; Jean, P.; Knoedlseder, J.; Ubertini, P.; Vedrenne, G.; Weidenspointner, G.; Wunderer, C.

    2006-01-01

    The next generation of instrumentation for nuclear astrophysics will have to achieve an improvement in sensitivity by a factor of 10-100 over present technologies. With the focusing gamma-ray telescope MAX we take up this challenge and propose to combine the required sensitivity with high spectral and angular resolution, and the capability to measure the polarization of the photons. MAX is a space-borne crystal diffraction telescope, featuring a broad-band Laue lens optimized for the observation of compact sources in two wide energy bands of high astrophysical relevance. Gamma rays will be focused from the large collecting area of a crystal diffraction lens onto a very small detector volume. As a consequence, the signal to background ratio is greatly enhanced, leading to unprecedented sensitivities

  11. Scattering with polarized neutrons

    International Nuclear Information System (INIS)

    Schweizer, J.

    2007-01-01

    In the history of neutron scattering, it was shown very soon that the use of polarized neutron beams brings much more information than usual scattering with unpolarized neutrons. We shall develop here the different scattering methods that imply polarized neutrons: 1) polarized beams without polarization analysis, the flipping ratio method; 2) polarized beams with a uniaxial polarization analysis; 3) polarized beams with a spherical polarization analysis. For all these scattering methods, we shall give examples of the physical problems which can been solved by these methods, particularly in the field of magnetism: investigation of complex magnetic structures, investigation of spin or magnetization densities in metals, insulators and molecular compounds, separation of magnetic and nuclear scattering, investigation of magnetic properties of liquids and amorphous materials and even, for non magnetic material, separation between coherent and incoherent scattering. (author)

  12. Polarized Light Corridor Demonstrations.

    Science.gov (United States)

    Davies, G. R.

    1990-01-01

    Eleven demonstrations of light polarization are presented. Each includes a brief description of the apparatus and the effect demonstrated. Illustrated are strain patterns, reflection, scattering, the Faraday Effect, interference, double refraction, the polarizing microscope, and optical activity. (CW)

  13. Shaping the spatial and spectral emissivity at the diffraction limit

    International Nuclear Information System (INIS)

    Makhsiyan, Mathilde; Bouchon, Patrick; Jaeck, Julien; Pelouard, Jean-Luc; Haïdar, Riad

    2015-01-01

    Metasurfaces have attracted a growing interest for their ability to artificially tailor an electromagnetic response on various spectral ranges. In particular, thermal sources with unprecedented abilities, such as directionality or monochromaticity, have been achieved. However, these metasurfaces exhibit homogeneous optical properties whereas the spatial modulation of the emissivity up to the wavelength scale is at the crux of the design of original emitters. In this letter, we study an inhomogeneous metasurface made of a nonperiodic set of optical nano-antennas that spatially and spectrally control the emitted light up to the diffraction limit. Each antenna acts as an independent deep subwavelength emitter for given polarization and wavelength. Their juxtaposition at the subwavelength scale encodes far field multispectral and polarized images. This opens up promising breakthroughs for applications such as optical storage, anti-counterfeit devices, and multispectral emitters for biochemical sensing

  14. Shaping the spatial and spectral emissivity at the diffraction limit

    Energy Technology Data Exchange (ETDEWEB)

    Makhsiyan, Mathilde [MiNaO, ONERA, The French Aerospace Lab, 91761 Palaiseau (France); MiNaO, Laboratoire de Photonique et de Nanostructures (LPN), CNRS, Université Paris-Saclay, route de Nozay, F-91460 Marcoussis (France); Bouchon, Patrick, E-mail: patrick.bouchon@onera.fr; Jaeck, Julien [MiNaO, ONERA, The French Aerospace Lab, 91761 Palaiseau (France); Pelouard, Jean-Luc [MiNaO, Laboratoire de Photonique et de Nanostructures (LPN), CNRS, Université Paris-Saclay, route de Nozay, F-91460 Marcoussis (France); Haïdar, Riad [MiNaO, ONERA, The French Aerospace Lab, 91761 Palaiseau (France); École Polytechnique, Département de Physique, 91128 Palaiseau (France)

    2015-12-21

    Metasurfaces have attracted a growing interest for their ability to artificially tailor an electromagnetic response on various spectral ranges. In particular, thermal sources with unprecedented abilities, such as directionality or monochromaticity, have been achieved. However, these metasurfaces exhibit homogeneous optical properties whereas the spatial modulation of the emissivity up to the wavelength scale is at the crux of the design of original emitters. In this letter, we study an inhomogeneous metasurface made of a nonperiodic set of optical nano-antennas that spatially and spectrally control the emitted light up to the diffraction limit. Each antenna acts as an independent deep subwavelength emitter for given polarization and wavelength. Their juxtaposition at the subwavelength scale encodes far field multispectral and polarized images. This opens up promising breakthroughs for applications such as optical storage, anti-counterfeit devices, and multispectral emitters for biochemical sensing.

  15. Techniques in polarization physics

    International Nuclear Information System (INIS)

    Clausnitzer, G.

    1974-01-01

    A review of the current status of the technical tools necessary to perform different kinds of polarization experiments is presented, and the absolute and relative accuracy with which data can be obtained is discussed. A description of polarized targets and sources of polarized fast neutrons is included. Applications of polarization techniques to other fields is mentioned briefly. (14 figures, 3 tables, 110 references) (U.S.)

  16. Neutron diffraction on pulsed sources

    International Nuclear Information System (INIS)

    Aksenov, V.L.; Balagurov, A.M.

    2016-01-01

    The possibilities currently offered and major scientific problems solved by time-of-flight neutron diffraction are reviewed. The reasons for the rapid development of the method over the last two decades has been mainly the emergence of third generation pulsed sources with a MW time-averaged power and advances in neutron-optical devices and detector systems. The paper discusses some historical aspects of time-of-flight neutron diffraction and examines the contribution to this method by F.L.Shapiro whose 100th birth anniversary was celebrated in 2015. The state of the art with respect to neutron sources for studies on output beams is reviewed in a special section. [ru

  17. Industrial applications of neutron diffraction

    International Nuclear Information System (INIS)

    Felcher, G.P.

    1989-01-01

    Neutron diffraction (or, to be more general, neutron scattering) is a most versatile and universal tool, which has been widely employed to probe the structure, the dynamics and the magnetism of condensed matter. Traditionally used for fundamental research in solid state physics, this technique more recently has been applied to problems of immediate industrial interest, as illustrated in examples covering the main fields of endeavour. 14 refs., 14 figs

  18. Neutron diffraction and Vitamin E

    Energy Technology Data Exchange (ETDEWEB)

    Harroun, T A; Marquardt, D; Katsaras, J; Atkinson, J, E-mail: tharroun@brocku.ca

    2010-11-01

    It is generally accepted that neutron diffraction from model membrane systems is an effective biophysical technique for determining membrane structure. Here we describe an example of how deuterium labelling can elucidate the location of specific membrane soluble molecules, including a brief discussion of the technique itself. We show that deuterium labelled {alpha}-tocopherol sits upright in the bilayer, as might be expected, but at very different locations within the bilayer, depending on the degree of lipid chain unsaturation.

  19. Diffraction dissociation and elastic scattering

    International Nuclear Information System (INIS)

    Verebryusov, V.S.; Ponomarev, L.A.; Smorodinskaya, N.Ya.

    1987-01-01

    In the framework of Regge scheme with supercritical pomeron a model is suggested for the NN-scattering amplitude which takes into account the contribution introduced to the intermediate state by diffraction dissociation (DD) processes. The DD amplitude is written in terms of the Deck model which has been previously applied to describing the main DD features. The calculated NN cross sections are compared with those obtained experimentally. Theoretical predictions for higher energy are presented

  20. Polarized Moessbauer transitions

    International Nuclear Information System (INIS)

    Barb, D.

    1975-01-01

    Theoretical aspects of the emission, absorption and scattering of polarized gamma rays are reviewed for a general case of combined magnetic and electric hyperfine interactions; various possibilities of obtaining polarized gamma sources are described and examples are given of the applications of Moessbauer spectroscopy with polarized gamma rays in solving problems of solid state physics. (A.K.)

  1. Geographical Income Polarization

    DEFF Research Database (Denmark)

    Azhar, Hussain; Jonassen, Anders Bruun

    inter municipal income inequality. Counter factual simulations show that rising property prices to a large part explain the rise in polarization. One side-effect of polarization is tendencies towards a parallel polarization of residence location patterns, where low skilled individuals tend to live...

  2. Calculation of polarization effects

    International Nuclear Information System (INIS)

    Chao, A.W.

    1983-09-01

    Basically there are two areas of accelerator applications that involve beam polarization. One is the acceleration of a polarized beam (most likely a proton beam) in a synchrotron. Another concerns polarized beams in an electron storage ring. In both areas, numerical techniques have been very useful

  3. Submicron X-ray diffraction

    International Nuclear Information System (INIS)

    MacDowell, Alastair; Celestre, Richard; Tamura, Nobumichi; Spolenak, Ralph; Valek, Bryan; Brown, Walter; Bravman, John; Padmore, Howard; Batterman, Boris; Patel, Jamshed

    2000-01-01

    At the Advanced Light Source in Berkeley the authors have instrumented a beam line that is devoted exclusively to x-ray micro diffraction problems. By micro diffraction they mean those classes of problems in Physics and Materials Science that require x-ray beam sizes in the sub-micron range. The instrument is for instance, capable of probing a sub-micron size volume inside micron sized aluminum metal grains buried under a silicon dioxide insulating layer. The resulting Laue pattern is collected on a large area CCD detector and automatically indexed to yield the grain orientation and deviatoric (distortional) strain tensor of this sub-micron volume. A four-crystal monochromator is then inserted into the beam, which allows monochromatic light to illuminate the same part of the sample. Measurement of diffracted photon energy allows for the determination of d spacings. The combination of white and monochromatic beam measurements allow for the determination of the total strain/stress tensor (6 components) inside each sub-micron sized illuminated volume of the sample

  4. Diffraction Techniques in Structural Biology

    Science.gov (United States)

    Egli, Martin

    2016-01-01

    A detailed understanding of chemical and biological function and the mechanisms underlying the molecular activities ultimately requires atomic-resolution structural data. Diffraction-based techniques such as single-crystal X-ray crystallography, electron microscopy, and neutron diffraction are well established and they have paved the road to the stunning successes of modern-day structural biology. The major advances achieved in the last 20 years in all aspects of structural research, including sample preparation, crystallization, the construction of synchrotron and spallation sources, phasing approaches, and high-speed computing and visualization, now provide specialists and nonspecialists alike with a steady flow of molecular images of unprecedented detail. The present unit combines a general overview of diffraction methods with a detailed description of the process of a single-crystal X-ray structure determination experiment, from chemical synthesis or expression to phasing and refinement, analysis, and quality control. For novices it may serve as a stepping-stone to more in-depth treatises of the individual topics. Readers relying on structural information for interpreting functional data may find it a useful consumer guide. PMID:27248784

  5. Neutron diffraction and lattice defects

    International Nuclear Information System (INIS)

    Hamaguchi, Yoshikazu

    1974-01-01

    Study on lattice defects by neutron diffraction technique is described. Wave length of neutron wave is longer than that of X-ray, and absorption cross-section is small. Number of defects observed by ESR is up to several defects, and the number studied with electron microscopes is more than 100. Information obtained by neutron diffraction concerns the number of defects between these two ranges. For practical analysis, several probable models are selected from the data of ESR or electron microscopes, and most probable one is determined by calculation. Then, defect concentration is obtained from scattering cross section. It is possible to measure elastic scattering exclusively by neutron diffraction. Minimum detectable concentration estimated is about 0.5% and 10 20 - 10 21 defects per unit volume. A chopper and a time of flight system are used as a measuring system. Cold neutrons are obtained from the neutron sources inserted into reactors. Examples of measurements by using similar equipments to PTNS-I system of Japan Atomic Energy Research Institute are presented. Interstitial concentration in the graphite irradiated by fast neutrons is shown. Defects in irradiated MgO were also investigated by measuring scattering cross section. Study of defects in Ge was made by measuring total cross section, and model analysis was performed in comparison with various models. (Kato, T.)

  6. Development of a superconducting radio frequency photoelectron injector

    International Nuclear Information System (INIS)

    Arnold, A.; Buettig, H.; Janssen, D.; Kamps, T.; Klemz, G.; Lehmann, W.D.; Lehnert, U.; Lipka, D.; Marhauser, F.; Michel, P.; Moeller, K.; Murcek, P.; Schneider, Ch.; Schurig, R.; Staufenbiel, F.; Stephan, J.; Teichert, J.; Volkov, V.; Will, I.; Xiang, R.

    2007-01-01

    A superconducting radio frequency (RF) photoelectron injector (SRF gun) is under development at the Research Center Dresden-Rossendorf. This project aims mainly at replacing the present thermionic gun of the superconducting electron linac ELBE. Thereby the beam quality is greatly improved. Especially, the normalized transverse emittance can be reduced by up to one order of magnitude depending on the operating conditions. The length of the electron bunches will be shortened by about two orders of magnitude making the present bunchers in the injection beam line dispensable. The maximum obtainable bunch charge of the present thermionic gun amounts to 80pC. The SRF gun is designed to deliver also higher bunch charge values up to 2.5nC. Therefore, this gun can be used also for advanced facilities such as energy recovery linacs (ERLs) and soft X-ray FELs. The SRF gun is designed as a 312 cell cavity structure with three cells basically TESLA cells supplemented by a newly developed gun cell and a choke filter. The exit energy is projected to be 9.5MeV. In this paper, we present a description of the design of the SRF gun with special emphasis on the physical and technical problems arising from the necessity of integrating a photocathode into the superconducting cavity structure. Preparation, transfer, cooling and alignment of the photocathode are discussed. In designing the SRF gun cryostat for most components wherever possible the technical solutions were adapted from the ELBE cryostat in some cases with major modifications. As concerns the status of the project the design is finished, most parts are manufactured and the gun is being assembled. Some of the key components are tested in special test arrangements such as cavity warm tuning, cathode cooling, the mechanical behavior of the tuners and the effectiveness of the magnetic screening of the cavity

  7. 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.

  8. Role of quantum-confined stark effect on bias dependent photoluminescence of N-polar GaN/InGaN multi-quantum disk amber light emitting diodes

    KAUST Repository

    Tangi, Malleswararao; Mishra, Pawan; Janjua, Bilal; Prabaswara, Aditya; Zhao, Chao; Priante, Davide; Min, Jung-Wook; Ng, Tien Khee; Ooi, Boon S.

    2018-01-01

    to be nitrogen polar (N-polar) verified using KOH wet chemical etching and valence band spectrum analysis of high-resolution X-ray photoelectron spectroscopy. The crystal structure and quality of the NWs were investigated by high-angle annular dark field

  9. Subcycle interference dynamics of time-resolved photoelectron holography with midinfrared laser pulses

    International Nuclear Information System (INIS)

    Bian Xuebin; Yuan, Kai-Jun; Bandrauk, Andre D.; Huismans, Y.; Smirnova, O.; Vrakking, M. J. J.

    2011-01-01

    Time-resolved photoelectron holography from atoms using midinfrared laser pulses is investigated by solving the corresponding time-dependent Schroedinger equation (TDSE) and a classical model, respectively. The numerical simulation of the photoelectron angular distribution of Xe irradiated with a low-frequency free-electron laser source agrees well with the experimental results. Different types of subcycle interferometric structures are predicted by the classical model. Furthermore with the TDSE model it is demonstrated that the holographic pattern is sensitive to the shape of the atomic orbitals. This is a step toward imaging by means of photoelectron holography.

  10. Scattering of polarized low-energy electrons by ferromagnetic metals

    International Nuclear Information System (INIS)

    Helman, J.S.

    1981-01-01

    A source of spin polarized electrons with remarkable characteristics based on negative electron affinity (NEA) GaAs has recently been developed. It constitutes a unique tool to investigate spin dependent interactions in electron scattering processes. The characteristics and working principles of the source are briefly described. Some theoretical aspects of the scattering of polarized low-energy electrons by ferromagnetic metals are discussed. Finally, the results of the first polarized low-energy electron diffraction experiment using the NEA GaAs source are reviewed; they give information about the surface magnetization of ferromagnetic Ni (110). (Author) [pt

  11. Characterization of a microfocused circularly polarized x-ray probe

    International Nuclear Information System (INIS)

    Pollmann, J.; Srajer, G.; Maser, J.; Lang, J. C.; Nelson, C. S.; Venkataraman, C. T.; Isaacs, E. D.

    2000-01-01

    We report on the development of a circularly polarized x-ray microprobe in the intermediate energy range from 5 to 10 keV. In this experiment linearly polarized synchrotron radiation was circularly polarized by means of a Bragg-diffracting diamond phase retarder and subsequently focused down to a spot size of about 4x2 μm 2 by a Fresnel zone plate. The properties of the microprobe were characterized, and the technique was applied to the two-dimensional mapping of magnetic domains in HoFe 2 . (c) 2000 American Institute of Physics

  12. Polarized neutron study of TbNi2

    International Nuclear Information System (INIS)

    Givord, D.; Givord, F.; Gignoux, D.; Koehler, W.C.; Moon, R.M.

    1976-01-01

    Neutron diffraction experiments have been carried out on a TbNi 2 single crystal. Below the Curie temperature, 42 K, a magnetic contribution is observed only on nuclear scattering peaks. Therefore, the terbium atoms form a ferromagnetic structure. Polarized neutron measurements performed in the paramagnetic state, in an applied magnetic field of 57 kOe, reveal a non-uniform polarization of the conduction band. Within the experimental accuracy, no 3d magnetic moment is observed on nickel atoms. This result is consistent with the assumption of rare earth magnetic ordering occurring through the polarization of conduction electrons. (author)

  13. Radially polarized conical beam from an embedded etched fiber.

    Science.gov (United States)

    Kalaidji, Djamel; Spajer, Michel; Marthouret, Nadège; Grosjean, Thierry

    2009-06-15

    We propose a method for producing a conical beam based on the lateral refraction of the TM(01) mode from a two-mode fiber after chemical etching of the cladding, and for controlling its radial polarization. The whole power of the guided mode is transferred to the refracted beam with low diffraction. Polarization control by a series of azimuthal detectors and a stress controller affords the transmission of a stabilized radial polarization through an optical fiber. A solid component usable for many applications has been obtained.

  14. Acceleration of polarized particles

    International Nuclear Information System (INIS)

    Buon, J.

    1992-05-01

    The spin kinetics of polarized beams in circular accelerators is reviewed in the case of spin-1/2 particles (electrons and protons) with emphasis on the depolarization phenomena. The acceleration of polarized proton beams in synchrotrons is described together with the cures applied to reduce depolarization, including the use of 'Siberian Snakes'. The in-situ polarization of electrons in storage rings due to synchrotron radiation is studied as well as depolarization in presence of ring imperfections. The applications of electron polarization to accurately calibrate the rings in energy and to use polarized beams in colliding-beam experiments are reviewed. (author) 76 refs., 19 figs., 1 tab

  15. New structural studies of liquid crystal by reflectivity and resonant X-ray diffraction; Nouvelles etudes structurales de cristaux liquides par reflectivite et diffraction resonante des rayons X

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, P

    2007-04-15

    This memory presents three structural studies of smectic Liquid Crystals by reflectivity and resonant diffraction of X-rays. It is divided in five chapters. In the first a short introduction to Liquid Crystals is given. In particular, the smectic phases that are the object of this study are presented. The second chapter is consecrated to the X-ray experimental techniques that were used in this work. The three last chapters present the works on which this thesis can be divided. Chapter three demonstrates on free-standing films of MHPOBC (historic liquid crystal that possesses the antiferroelectric sub-phases) the possibility to extend the technique of resonant X-ray diffraction to liquid crystals without resonant element. In the fourth chapter the structure of the B{sub 2} liquid crystal phase of bent-core molecules (or banana molecules) is elucidated by using resonant X-ray diffraction combined with polarization analysis of the diffracted beam. A model of the polarization of the resonant beam diffracted by four different structures proposed for the B{sub 2} phase is developed in this chapter. In the fifth chapter a smectic binary mixture presenting a very original critical point of phase separation is studied by X-ray reflectivity and optical microscopy. A concentration gradient in the direction perpendicular to the plane of the film seems to be induced by the free-standing film geometry. The results of a simplified model of the system are compatible with this interpretation.

  16. Polarization effects. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    Courant, E.

    1981-01-01

    The use of polarized proton beams in ISABELLE is important for several general reasons: (1) With a single longitudinally polarized proton beam, effects involving parity violation can be identified and hence processes involving weak interactions can be separated from those involving strong and electromagnetic interactions. (2) Spin effects are important in the strong interactions and can be useful for testing QCD. The technique for obtaining polarized proton beams in ISABELLE appears promising, particularly in view of the present development of a polarized proton beam for the AGS. Projections for the luminosity in ISABELLE for collisions of polarized protons - one or both beams polarized with longitudinal or transverse polarization - range from 1/100 to 1 times the luminosity for unpolarized protons.

  17. The Physics of Polarization

    Science.gov (United States)

    Landi Degl'Innocenti, Egidio

    2015-10-01

    The introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.

  18. Photoelectron angular distribution parameters for elements Z=55 to Z=100 in the photoelectron energy range 100-5000 eV

    CERN Document Server

    Trzhaskovskaya, M B; Yarzhemsky, V G

    2002-01-01

    Presented here are parameters of the angular distribution of photoelectrons along with the subshell photoionization cross sections for all atoms with 55<=Z<=100 and for atomic shells with binding energies lower than 2000 eV. The parameters are given for nine photoelectron energies in the range 100-5000 eV. Relativistic calculations have been carried out within the quadrupole approximation by the use of the central Dirac-Fock-Slater potential. The effect of the hole resulting in the atomic subshell after photoionization has been taken into account in the framework of the frozen orbital approximation.

  19. Diffractive dijet and W production in CDF

    International Nuclear Information System (INIS)

    Goulianos, K.

    1998-01-01

    Results on diffractive dijet and W-boson production from CDF are reviewed and compared with predictions based on factorization of the diffractive structure function of the proton measured in deep inelastic scattering at HERA

  20. A theoretical overview on single hard diffraction

    International Nuclear Information System (INIS)

    Wuesthoff, M.

    1996-01-01

    The concept of the Pomeron structure function and its application in Single Hard Diffraction at hadron colliders and in diffractive Deep Inelastic Scattering is critically reviewed. Some alternative approaches are briefly surveyed with a focus on QCD inspired models