bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra fast H+ Desorption from an Isolated NH3 Monolayer Adsorbed on a Xe Film Induced by a Resonant Core Electron Transition Studied by Auger Electron-Photoion Coincidence Spectroscopy
Authors: Nagasono Mitsuru , Mase Kazuhiko , Tanaka Shin-ichiro , Urisu Tsuneo
Published: March 2014

Mechanism of ion desorption from an isolated NH3 monolayer adsorbed on a Xe film (NH3/Xe) induced by a resonant core electron excitation is studied using Auger electron-photoion coincidence (AEPICO) spectroscopy. The total ion yield spectrum of NH3/Xe exhibits a threshold peak at the resonant excitation from N 1s to the 4a
1 N-H antibonding orbital. The Auger electron spectrum of the isolated NH3 at the 4a
1←N 1s resonant transition is found to be mainly due to spectator-Auger transitions. A series of AEPICO spectra at the 4a
1←N 1s resonance is measured for the electron kinetic energies corresponding to the spectator Auger transitions. The AEPICO spectra show that H+ is the only desorbed ion species. The electron kinetic energy dependence of the H+ AEPICO yield displays a structure similar to that of the spectator-Auger electron spectrum. This result indicates that the H+ desorption probabilities are independent of the final states of spectator-Auger transitions. Based on these results, we suggest that the repulsive potential surface of the (N 1s)-1(4a
1)1 state is responsible for the H+ desorption, that is, ultrafast H+ desorption mechanism is favorable in this system.
Change in Electronic Structure of C60 Molecules Adsorbed on a Si(001)-(2×1) Surface by Thermal Effect
Authors: Kondo Daiyu , Sakamoto Kazuyuki , Ushimi Yoshimitsu , Harada Masashi , Kimura Akio , Kakizaki Akito , Suto Shozo
Published: March 2014

We report here the temperature-dependent electronic structure of C60 molecules adsorbed on a Si(001)-(2×1) surface, measured by photoelectron spectroscopy. At room temperature, the valence spectra reveal that the interaction between a 1 monolayer (ML) C60 film and a Si(001)-(2×1) surface is mainly a physisorption. After annealing the 1 ML C60 film adsorbed on a Si(001)-(2×1) surface at 500 K, in the valence spectra the highest occupied molecular orbital (HOMO) of a C60 molecule splits into two peaks. The binding energies of the two peaks are 1.6 and 2.1 eV. We assign the 1.6-eV peak to the shifted HOMO and the 2.1-eV peak to the bonding state between C60 molecules and a Si(001)-(2×1) surface from the polarization-dependent measurement and the Si 2p core level spectrum. Moreover, the molecular orbitals and the C 1s core level of a C60 molecule shift to the lower binding energy side. These results indicate that the interaction between C60 molecules and the Si(001)-(2×1) surface changes from physisorption to chemisorption, which has both covalent and ionic characters, at 500 K.
Grazing Incidence X-Ray Fluorescence and Scattering Experiments at BL-39XU, SPring-8
Authors: Sakurai Kenji , Eba Hiromi , Goto Shunji
Published: March 2014

3rd-generation synchrotron radiation has enabled remarkable progress to be made in ultra trace analysis by total-reflection X-ray fluorescence as well as in surface/interface morphology study by specular and non-specular X-ray scattering. A new grazing incidence X-ray spectro-reflectometer has been recently installed at the undulator beamline BL-39XU, SPring-8. The present paper gives recent preliminary results obtained during commissioning.
Angle-Resolved UPS Study of Oriented Thin Film of Tetratetracontane (n-C44H90) on Cu(100) and Theoretical Simulation by IAC Approximation
Authors: Yoshimura D. , Ishii H. , Ouchi Y. , Ito E. , Miyamae T. , Hasegawa S. , Ueno N. , Seki K.
Published: March 2014

The electronic structure and molecular orientation of tetratetracontane (n-C44H90; TTC) ultra-thin film on Cu(100) were studied by angle-resolved UPS (ARUPS). We observed 2×1 like LEED pattern at room temperature. This indicates that the TTC molecule lies on the Cu(100) surface with its chain axis parallel to the Cu[110] direction. The application of the dipole selection-rule to normal emission spectrum revealed that the C-C-C plane of TTC is parallel to the surface (flat-on orientation). We also examined the dependence of the photoemission spectra on the take-off angle, and observed clear one-dimensional intramolecular energy-band dispersion. The simulated spectra for flat-on orientation based on independent-atomic-center (IAC) approximation combined with ab initio MO calculations are in good agreement with the observed spectra. These results verify the deduced molecular orientation and demonstrate the reliability of theoretical simulation with IAC approximati on.
Study of Magnetic Materials Using Spin-Resolved Circularly-Polarized Resonant Photoemission
Authors: Tjeng L. H. , Brookes N. B. , Goedkoop J. B. , Sinkovic B. , Groot F. M. F. De , Hesper R. , Altieri S. , Pellegrin E. , Tanaka Arata , Hulbert S. L. , Shekel E. , Hien N. T. , Menovsky A. A. , Sawatzky G. A.
Published: March 2014

We have recently demonstrated that it is possible to obtain spin-resolved valence band spectra with a very high degree of spin polarization from macroscopically non-magnetic transition metal materials if the excitation light is circularly polarized and has an energy close to the cation 2p3/2 (L3) white line. Using the layered compound Sr2CuO2Cl2 as a test system, we report in this paper that the degree of spin polarization is strongly dependent on the transition metal 3d orbital orientation relative to the Poynting vector of the light.
Theoretical Study of X-Ray Emission Spectroscopy on Magnetic Materials
Authors: Kotani Akio
Published: March 2014

Theoretical analyses of resonant X-ray emission spectroscopy (RXES) in rare earth compounds and transition metal compounds are given with an impurity Anderson model using the coherent second order optical formula. RXES provides us with important information on the 4f and 3d electronic states in the ground state of these materials, as well as excited states with and without a core hole. For the analysis of RXES of rare earth systems, the impurity Anderson model (including a single rare earth ion) works well, but we need larger clusters in order to explain some aspects of RXES in transition metal compounds.
Characterization of Electrocatalysts by In Situ SAXS and XAS Investigations
Authors: Haubold H.-G. , Hiller P. , Jungbluth H. , Vad T.
Published: March 2014

Size distributions, oxidation states and surface coverage of Pt catalyst particles on carbon supports were studied by anomalous small angle scattering (ASAXS) and X-ray absorption (XANES) with X-ray energies near the Pt-L3 absorption edge. The measurements were performed in electrochemical cells to trace electrochemical reactions in situ as a function of the applied electrochemical potential. In potential sweep experiments combined in situ ASAXS and XAS measurements give direct information on the electrochemical processes of methanol oxidation and iodine adsorption on the catalyst surface.
Spin Resolved Photoemission Excited by VUV-Circularly Polarized Radiation: Application to Ferromagnetic Ni
Authors: Kimura Akio , Sawada Masahiro , Qiao Shan , Harasawa Ayumi , Kakizaki Akito
Published: March 2014

We have performed spin- and angle- resolved photoemission spectroscopy for the Ni 3d valence band using vuv-circularly polarized synchrotron radiation (hν = 60 - 80eV) from helical undulator of Photon Factory in KEK. The experiment was performed using our recently developed spin-resolving photoemission spectrometer with compact retarding type Mott detector and hemispherical analyzer. We have observed clear magnetic circular dichroism (MCD) especially in the minority spin bands.
Photoelectron Spectroscopy and Magnetic Properties of Manganese Pnictides Nanocrystals Formed on Passivated GaAs Substrates
Authors: Oshima Masaharu , Ono Kanta , Mizuguchi Masaki , Uragami Takeshi , Fujioka Hiroshi , Tanaka Masaaki , Watanabe Yoshio
Published: March 2014

We first report the formation and magnetic properties of MnAs and MnSb nanocrystals by “super Volmer-Weber epitaxy” utilizing very low surface energy substrates such as sulfur-passivated GaAs substrates. On the S-passivated GaAs surface, MnAs dots with the size of about 16 nm and the density of 2×1010 cm-2 were successfully grown. SQUID analysis of these dots showed partly vertical easy magnetization axis. However, on the Se-GaAs surface, no MnAs dots were grown. SRPES revealed that Se atoms were segregated to the MnAs surface, probably playing a role of surfactant for the layer growth mode.
5d and 4f Magnetic Profiles in Ce/Fe Multilayers Probed by XRMS
Authors: Sève L. , Jaouen N. , Tonnerre J. M. , Raoux D. , Arend M. , Felsch W. , Bartolome F. , Rogalev A. , Goulon J. , Chakarian V.
Published: March 2014

The element and electronic shell specificities of x-ray resonant magnetic scattering have been used to investigate the induced magnetization of the 5d and 4f electronic states of Ce in a [Ce(10Å)/Fe(30Å)]×100 multilayer. We show that the measurement of the magnetic contribution to the intensities diffracted at low angles at the L2 and M4 edge of the rare-earth allows to investigate the profile of the 5d and 4f magnetic polarisation across the rare-earth layer. The Ce 5d polarization is found to be oscillating across the Ce layer with a slow decrease from the interfaces with Fe towards the center of the layer. Preliminary results on the Ce 4f polarisation indicate a constant profile.
Anisotropic Arrangement of Mo Species Highly Dispersed on TiO2(110) Surface Demonstrated by Polarization Dependent Total Reflection Fluorescence EXAFS
Authors: Asakura Kiyotaka , Chun Wang-Jae , Iwasawa Yasuhiro
Published: March 2014

Mo species on TiO2(110) surface were studied by means of Polarization Dependent Total Reflection Fluorescence EXAFS. The structure and orientation of Mo species are strongly affected by the pretreatment conditions and impurity. Mo dimer oriented to [11̄0] direction and Mo chain structure along [001] are present when they are prepared under oxidative conditions and reductive conditions, respectively. On the other hand, Mo tetrahedral monomer is formed when Na+ and K+ are present on the surface.
Theory of Orbital Orderings and Excitations in Perovskite Manganites –Their Observation by Resonant X-ray Scattering–
Authors: Ishihara Sumio , Maekawa Sadamichi
Published: March 2014

The orbital orderings and excitations in perovskite manganites and experimental methods for their observation by resonant x-ray scattering are theoretically investigated. In the elastic scattering for the ordering, an origin of the orbital dependence of the atomic scattering factor is identified and a method to distinguish several types of the orbital ordering is considered. As a probe to detect the orbital excitation, a possible mechanism by the resonant inelastic x-ray scattering is proposed.
EXAFS Study on Local Structural Changes in Amorphous Fe–Zr–B Alloys
Authors: Nakata Yoshiyuki , Hara Naoyuki , Hirotsu Yoshihiko , Emura Shuichi , Makino Akihiro , Uruga Tomoya , Harada Makoto , Nishihata Yasuo , Yoneda Yasuhiro , Kubozono Yoshihiro
Published: March 2014

The EXAFS spectra on Zr K-edge are investigated for as-formed Fe-7at%Zr-3at%B amorphous alloys and annealed ones at 693K and 773K for an hour in order to reveal local structural changes due to annealing. The analysis shows that the atomic distances of Fe-Zr and Zr-Zr pairs increase during annealing and approach those in a Fe3Zr or/and Fe2Zr metallic compound. The change in the atomic distances suggests that medium range ordered clusters should be formed during annealing.
High-Pressure Mössbauer Study of FeS with Nuclear Forward Scattering of Synchrotron Radiation
Authors: Kobayashi Hisao , Yoda Yoshitaka , Kamimura Takashi
Published: March 2014

The delay-time spectra of the nuclear resonant forward scattering for FeS were measured at ambient conditions with the sample not–enriched in 57Fe and under high pressure using the sample with enriched about 10 at.% 57Fe. The quantum beat modulations in observed delay–time spectra under pressure change with two successive first–order phase transitions at 3.5 and 6.5 GPa. We have successfully analyzed the beat patterns in delay–time spectra using the maximum entropy method and extracted the frequencies in each phase. These frequencies are in good agreement with those expected form the hyperfine interactions which values were estimated by the analysis of Mössbauer absorption spectra. This is the first successful attempt to apply the maximum entropy method in this field.
Nuclear Resonant Scattering of Ferromagnetic Amorphous Ribbon
Authors: Kobayashi Yasuhiro , Nasu Saburo , Nakamichi Takashi , Sato Masayuki , Seto Makoto , Yoda Yoshitaka
Published: March 2014

We performed 57Fe nuclear forward scattering experiments using a ferromagnetic (Co0.94Fe0.06)74.5Si13.5B12 amorphous ribbon at BL09XU of SPring-8. The observed NFS spectra of the amorphous ribbon show quantum beats that decay faster than the expected from the lifetime. This fast decay is due to the distribution of the hyperfine magnetic fields. Decay rate determined from NFS in the amorphous is about 2.5 times shorter than that of isolated 57Fe nuclei. This value is similar to one expected from the apparent peak width of the ordinary transmission Mössbauer spectra.
M2,3 Edge Core-level Magnetic Circular Dichroism Measurements of Cu/Co Multilayers
Authors: Kawaguchi Shinichi , Ono Kanta , Horiba Koji , Mizuguchi Masaki , Hayakawa Shinjiro , Fujioka Hiroshi , Koide Tsuneharu , Miyauci Hiroshi , Nakajima Nobuo , Takenaka Hisataka , Oshima Masaharu
Published: March 2014

We have carried out the magnetic circular dichroism (MOD) measurements in the VUV region near M2,3 absorption edges of Cu and Co for Cu/Co multilayers in order to investigate the perpendicular magnetization of the system. Circularly polarized SR light was incident almost normal to the sample surface and the reflected light was detected, corresponding to the information about perpendicular magnetic moments. The MCD spectrum of the magnetic layers at Co M2,3 edges showed one negative peak. Although Cu is non-magnetic, a similar MCD profile was obtained for Cu M2,3 edges. These results indicate that the perpendicular magnetic moments of non-magnetic Cu are induced near the Cu/Co interfaces of multilayers and the directions of the magnetic moments in Cu and Co layers are parallel with each other along the direction of applied magnetic field.
X-ray Polarization Analysis of Orbital Ordered State in La0.88Sr0.12MnO3
Authors: Fukuda Tatsuo , Hirota Kazuma , Kimura Hiroyuki , Murakami Youichi , Nishizawa Akinori , Endoh Yasuo
Published: March 2014

Hole-doped lanthanum manganites La1-x
Sr
x
MnO3 have been revisited since the discovery of colossal magnetoresistance (CMR). In this system, orbital as well as spin and charge degrees of freedom have attracted much attention. However, direct observation of orbital ordering (OO) is very difficult and there have been few experiments. Recently, Murakami et al. [Phys. Rev. Lett. 80 (1998) 1932, Phys. Rev. Lett. 81 (1998) 582] observed the azimuthal-angle dependence of OO superlattice peaks in La0.5Sr1.5MnO4 and LaMnO3 by resonant x-ray diffraction, which is sensitive to the anisotropy of the structure factor. It is also known that the OO peak changes the polarization of photons from σ to π', which was also observed by Murakami et al. in LaMnO3. We confirmed that the (0 3 0) reflection of La0.88Sr0.12MnO3 is an OO superlattice peak using synchrotron resonant x-ray diffraction, and then carried out polarization analysis of the OO superlattice peak. While the azimuthal-angle dependence of (0 3 0) shows a clear two-fold dependence, the polarization dependence is somewhat obscure. We found that the peak consists of two parts, one of which shows a σ→π' polarization and the other shows a σ→σ' behaviour. We speculate the latter is an extrinsic contamination, though the origin is unknown.
XAFS Study on Nitrogenation of CoTiSn
Authors: Nobata Tatsuhito , Nakamoto Go , Kurisu Makio , Makihara Yoshikazu , Tokuyoshi Tetsuo , Nakai Ikuo
Published: March 2014

Gas-phase nitrogenation of CoTiSn compound with the MgAgAs-type structure has been examined by means of x-ray diffraction (XRD) and x-ray absorption fine structure (XAFS). The XRD suggests that the nitrogenation product is composed of the corresponding Cu2MnAl-type compound with expanded unit-cell volume comparable to that of Co2TiSn and subtle trace of Ti6Sn5 and Sn. Whereas the x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra for the Ti, Co and Sn K-edges clearly indicate the coexistence of TiN and Co1+yTiSn phases in the product. It is also revealed that more Co atoms than expected from the chemical formulas are introduced into the vacancy site of the MgAgAs structure in Co1+yTiSn with 0≤y≤0.4.
High Energy XAFS Study of Sm:K-edge in Sm2Fe17Nx
Authors: Kasatani Hirofumi , Ohmura Masashi , Yokoyama Katsumi , Kobayashi Kurima , Nishihata Yasuo , Yagi Kenichiro , Terauchi Hikaru
Published: March 2014

High energy XAFS studies of Sm:K-edge in Sm2Fe17N
x
with x=0.0, ≦0.1, 0.5, 2.0 and 3.0 were carried out at room temperature in order to clarify the relation between the local structure around the Sm-atom and the change of the magnetic property due to the absorption of nitrogen atom. In the XANES region, we firstly found the change of Sm electron state by nitriding because of the change of the shape in the absorption edge jump. In the result of the EXAFS spectra, we confirmed that the Sm-Fe distance was expanded monotonously due to the absorption of N-atom.
X-ray Magnetic Bragg Scattering of SmFe2
Authors: Miyagawa Hayato , Tominaga Teruo , Nakamura Tetsuya , Watanabe Yasuhiro , Ito Masahisa , Adachi Hiromichi , Kawata Hiroshi , Nakao Susumu
Published: March 2014

X-ray non-resonant magnetic Bragg scattering was measured for SmFe2 which magnetic structure has not yet been studied by neutron diffraction. The measurement was performed along the (h h 0) planes using white elliptically polarized synchrotron radiation at BL3C2 (KEK-PF). From the profiles at the reflections (4h+2 4h+2 0) to which only Sm atom contributes, the form factors of the spin and orbital magnetic moments of Sm3+ have been directly deduced.
Iron-Oxide Interlayer Existing in Ba-Ferrite/Sapphire(001) Films Grown by Sputtering
Authors: Cho Tae Sik , Doh Seok Joo , Je Jung Ho , Noh Do Young
Published: March 2014

We revealed the existence of a very thin (∼50 Å thick) epitaxial iron-oxide interlayer in amorphous Ba-ferrite thin films on sapphire(001) using synchrotron x-ray scattering. Depending on the sputtering gases used in radio frequency sputtering deposition, two different iron-oxide interlayers were formed; non-magnetic α-Fe2O3 interlayer by pure Ar gas and ferromagnetic Fe3O4 interlayer by Ar-10% O2 gas mixture. The α-Fe2O3 interlayer much more promoted the crystallization of amorphous Ba-ferrite, compared to the Fe3O4 interlayer. We suggest that the interlayer existing between amorphous Ba-ferrite and sapphire substrate greatly contributes to the reduction of the activation energy for the crystallization of amorphous Baferrite film.
Anomalous X-ray Scattering (AXS) Study on the Local Ordering Structure around Ni and Cu in Amorphous Pd40Ni10Cu30P20 Alloy
Authors: Park Changyong , Saito Masatoshi , Nishiyama Nobuyuki , Inoue Akihisa , Waseda Yoshio
Published: March 2014

The anomalous X-ray scattering (AXS) measurements have been made for determining the local ordering structure around Ni and Cu in amorphous Pd40Ni10Cu30P20 alloy, which exhibits wide supercooled liquid region and high reduced glass transition temperature, by using the synchrotron radiation at incident X-ray energies close to the K-absorption edge of Ni and Cu. The resultant structural functions indicate that the atomic arrangement around Cu differs from that around Ni in this particular amorphous alloy.
A Charge Density Study of MgCu2 and MgZn2 by the Maximum Entropy Method
Authors: Kubota Yoshiki , Takata Masaki , Sakata Makoto , Ohba Takuya , Kifune Kouichi , Tadaki Tsugio
Published: March 2014

The charge density distributions of the Mg-base Laves phase MgCu2 and MgZn2 were obtained from the synchrotron powder diffraction data by the Maximum Entropy Method (MEM). In the MEM charge density, the overlapped electron densities were found between Cu-Cu atoms in the case of MgCu2 and between Zn-Zn atoms. These covalent bonds form the electronic kagomé network for the both compounds. By the geometrical consideration, this characteristic feature can be interpreted as the existence of p3d3 hybridization of the Cu and Zn atoms. On the other hand, there were no such overlapped densities around Mg atoms, which denies any significant covalency between Mg and Cu or between Mg and Zn atoms. Furthermore, the peculiar distortion of the covalent bond network is found in the obtained MEM charge densities for the both compounds, that is, the covalent bonds are shifted towards the Mg atoms. This rather unusual bond nature should be due to the ionic interaction between the hybridized orbital and positively charged Mg ions. As for the MgZn2, the difference of the hybridized electron density was found related to the zigzag pattern of hexagonal stacking sequence.
Identification of Nature of Dislocation Loops Grown as Vacancy Source after Up-Quenching
Authors: Mizuno Kaoru , Nagai Shin-ya , Tamiya Atsuhiro , Noda Yasutoshi , Okitsu Kouhei , Hashimoto Eiji , Kino Takao
Published: March 2014

The dislocation loops grown as vacancy source after up-quenching in 99.9999 % aluminum single crystals with a low dislocation density were examined by synchrotron topography in order to determine the Burgers vector and the nature directly. The specimen crystal was heated to 295°C and hold for 15min. at the temperature, then cooled down to room temperature to freeze the loops in the specimen. Topographs were taken on the high-speed X-ray topographic station (BL-15B) at the Photon Factory (KEK-PF). White beam topographs were taken using four of symmetrically equivalent 111 and 220 reflections for the determination of the Burgers vector. Monochromatic section topographs were also taken with 111, 222, 333 and 444 reflections at a wavelength of 0.62Å. The image of the loops was simulated by numerical solution of the Takagi-Taupin equations. Burgers vector of the frozen loops was determined to be a/2<110>. And comparison between the observed loop image and the simulated one showed that the dislocation loop grown as a vacancy source was interstitial-type and the size ranged from 3 µ m to 10 µ m in radius.
Diffuse X-ray Scattering Studies on Defect Clusters in Ni Irradiated by High-Energy Ions and Electrons
Authors: Yuya Hideki , Matsui Tsuneo , Shigematsu Hirotake , Maeta Hiroshi , Ohtsuka Hideo , Sugai Hiroyuki , Iwase Akihiro
Published: March 2014

Pure Ni was irradiated with high-energy (150MeV Phosphorus) ions up to doses of 5.3×1013, 1.6×1014 and 4.1×1014 ions/cm2 and with 2MeV electrons up to 3×1018 e-/cm2. The resulting defect structures were studied at room temperature using diffuse X-ray scattering (DXS) methods. The size distribution of dislocation loops was analyzed by fitting the theoretical diffuse X-ray scattering intensities of the dislocation loops to the experimental ones. The number density of vacancy loops increased linearly with dose whereas their sizes did not increase. This implies that a vacancy-loop was formed by single cascade. On the other hand, the size of interstitial loops for the case of high-energy ion-irradiation was smaller than that for electron-irradiation, indicating the annihilation of free interstitials contributing to the formation of large interstitial-loops for high-energy ion-irradiation.
Local Structure of Liquid IVb–Te Mixtures
Authors: Yoshioka Shinya , Kawakita Yukinobu , Kanehira Makoto , Takeda Shin'ichi
Published: March 2014

Liquid binary alloys between Te and IVb elements such as Ge, Sn and Pb show anomalous electrical properties around the equiatomic composition and have a tendency of compound forming effect in the liquid state. These alloy systems have also the eutectic region around 85 at. % Te. To make clear local structure around IVb and Te atoms, we have measured extended X-ray absorption fine structure (EXAFS) for liquid Ge15Te85 and Sn16Te84 mixtures. The results for liquid Ge15Te85 mixture suggest that bonding state between Ge and Te decreases and becomes weak abruptly with increasing temperature and has more ionic character at higher temperature. In contrast to liquid Ge15Te85 mixture, local structure of liquid Sn16Te84 doesn't show large temperature dependence.
Investigation of the Local Structure of Vanadium Silicalite Catalyst (VS-1) Using XAFS, FT-IR and Photoluminescence Spectroscopic Methods
Authors: Higashimoto Shinya , Matsuoka Masaya , Yamashita Hiromi , Anpo Masakazu
Published: March 2014

The in situ characterization of the vanadium silicalite catalyst (VS-1) was carried out using XAFS (XANES, EXAFS), FTIR and dynamic photoluminescence techniques. The FT-IR spectrum of the VS-1 catalyst at around 960 cm-1 showed the incorporation of vanadium atoms into the zeolite framework. Furthermore, XAFS measurements have indicated that the VS-1 catalyst consists of highly dispersed vanadium oxide species having a tetrahedral coordination. The VS-1 catalyst exhibited an absorption band at around 300 nm and an intense photoluminescence with a vibrational fine structure at around 450-550 nm which could be attributed to the charge transfer processes on the tetrahedral vanadium oxide species involving an electron transfer from O2- to V5+ and reverse radiative decay, respectively. These results have indicated that a highly dispersed vanadium oxide species is present within the zeolite framework as a tetrahedrally coordinated species and the charge transfer excited state of this oxide species can be well-localized in the shorter V=O bond.
Local Structure of Compound-Forming Liquid Alloys
Authors: Kawakita Yukinobu , Yoshioka Shinya , Hiraishi Ikuo , Kanehira Makoto , Takeda Sin'ichi
Published: March 2014

Liquid alloys between Te and multi-valent metals such as Ga, In and Sn alloys are classified as compound-forming liquid alloys since their electrical properties show anomalous compositional dependence around their stoichiometric composition. Their local structures have been determined from EXAFS analysis. Liquid Ga40Te60 and In40Te60 have a network strcuture just above the melting points which is composed of three-fold In atoms and two-fold Te atoms bonding to them, but this structure is unstable with increasing temperature. Liquid Sn50Te50 is expected to have a looser bonding between Sn and Te compared with liquid In-Te mixtures from EXAFS and neutron diffraction measurements.
XANES Spectra of Mechanically Alloyed YFe
Authors: Tokuyoshi Tetsuo , Nakai Ikuo
Published: March 2014

To investigate change in electronic states by phase transformation during the mechanical alloying, we measured X-ray absorption near edge structure (XANES) spectra for mechanically alloyed YFe (m-YFe). The m-YFe powders were synthesized from a mixture of pure element powders. The structure of m-YFe powders was characterized by X-ray diffraction. After 120 h of milling the pattern becomes a broad reflection, which means that the specimen is in an amorphous state. We have found that a peak in Fe edge XANES spectra increases with the milling time. The energy of the pre-edge also shifts to the lower energy.
XANES Study on Phase Transformation of Amorphous Y2Fe
Authors: Nakai Ikuo , Tokuyoshi Tetsuo
Published: March 2014

Phase transformation in mechanical alloying Y2Fe has been investigated by means of x-ray absorption near edge structure (XANES) and x-ray diffraction (XRD) measurements. Milling changes mixture of crystalline powders of Fe and Y to an inhomogeneous amorphous material Y2Fe, which is subsequently transformed into some crystalline phase with homogeneous amorphous matrix. The pre-edge of Fe K absorption grows during the crystalline to amorphous transformation and decays for changing from the amorphous phase to the amorphous-crystalline mixed state. The energy of the pre-edge also shifts in the sequential phase transformation.
XANES Spectra in the Solid State Reaction of Y2Ni
Authors: Nakai Ikuo , Tokuyoshi Tetsuo
Published: March 2014

X-ray absorption near edge structure (XANES) and x-ray diffraction (XRD) investigations for a mechanically alloyed Y2Ni system are presented. From XRD measurements we find a phase transformation from mixture of crystalline Ni and Y into a single phase of an amorphous state by mechanical alloying for 80 h. The XANES spectrum at the Ni K edge have a pre-peak, which increases remarkably with increasing the milling time and becomes as sharp as that of a melt spun amorphous Y67Ni33 alloy. The energy position of the pre-peak also shifts to the lower energy side with the milling time.
Pressure-Variation of Structure Factor of Liquid Rb
Authors: Chihara Junzo , Kahl Gerhard
Published: March 2014

We have calculated the atomic and the electronic structures of compressed liquid rubidium under high pressures up to 6 GPa on the basis of the quantal hypernetted chain equations in combination with the Rosenfeld bridge functional. The calculated structure factors are in reasonable agreement with the experimental results by Tsuji et al. under these high pressures using synchrotron radiation. All structure factors calculated for this pressure-variation coincide almost into a single curve if wavenumbers are scaled in units of the Wigner-Seitz radius; the compression in liquid rubidium is uniform with increasing pressures. The effective ion-ion interactions remains almost unchanged under this pressure-variation. Results of calculation on liquid lithium confirm that effective ion-ion potentials for alkali metals have the specific feature of scaling property in common. Furthermore, it is shown that the uniform compression of liquid Rb can be explained simply by the effective ion-ion interaction based on the Aschcroft pseudopotenital at the room pressure with use of the scaling property.
Photoemission Study of D03-related (Fe1-xVx)3Al Alloys
Authors: Soda Kazuo , Takeuchi Tsunehiro , Yanagida Yohei , Mizutani Uichiro , Kato Masaaki , Nishino Yoichi , Sekiyama Akira , Imada Shin , Suga Shigemasa , Matsushita Tomohiro , Saito Yuji
Published: March 2014

We have measured photoelectron spectra of D03-related pseudo-binary alloys (Fe1-x
V
x
)3Al with the excitation photon energy around their transition-metal M
2,3 and L
2,3 edges in order to clarify their electronic structures. The valence band spectrum for x=0.33, Fe2VAl, shows a peak at the binding energy E
B of 1.1 eV with a shoulder around E
B=3 eV, while the spectrum for x=0, Fe3Al, has a relatively narrow peak at E
B=1 eV. The resonance behavior across the M
2,3 edges suggests that the Fe 3d states in Fe2VAl are distributed over the whole main valence band, particularly near the Fermi level and the shoulder structure, and that the V 3d states contribute to the 1.1 eV peak. The s
p bands become observable around E
B=7 eV in the spectra measured with the photon energy near the L
2,3 edges. Comparison is made of the obtained spectra with available theoretical works for the band structure as well as of the resonance behaviors in the M
2,3 and L
2,3 edge regions.
Local Structures for Ni–Mn Alloys
Authors: Miyanaga T. , Okazaki T. , Babanov Yu. A. , Ryazhkin A. V.
Published: March 2014

A new method to determine of the nearest neighbor (1NN) coordination numbers for binary disordered alloys is proposed. The method is reduced to the solution of the system of linear algebraic equations for the partial coordination numbers. As input data we use 1NN partial interatomic distances obtained independently for each EXAFS spectrum in binary alloy and the Debye-Waller factors.
Coordination numbers and interatomic distances for 75 and 80 at.% Ni-Mn alloys in ordered and disordered states are presented.
Charge Densities and Chemical Bonding of CaSi2
Authors: Nishibori Eiji , Saso Daisuke , Takata Masaki , Sakata Makoto , Imai Motoharu
Published: March 2014

The charge density distribution map of CaSi2 was obtained by the Maximum Entropy Method(MEM) using synchrotron powder diffraction data. The MEM charge density map reveals that there are two types of Si layers in a unit cell. In both layers, Si atoms form rather strong covalent bond. However, they are not identical. Electron density at bond mid point are slightly different at each layer, i.e. 0.62[e/Å3] for one layer, and 0.52[e/Å3] for the other. These values shows covalent bond of the former layer is considerably stronger than that of the latter layer. As for the bond lengths, the Si-Si bond length of the former layer is 2.32 Å and that of the latter is 2.40 Å, respectively. The present direct observation of bond electrons gives one of the examples that the longer the bond length, the weaker the covalent bond. It is not recognized that there exists covalency between Ca-Ca atoms. Since the MEM charge density shows very slight overlap of electron clouds between Ca-Si, the nature of chemical bond of Ca in CaSi2 is almost ionic.
XAFS Study of Amorphous Aluminium Alloy Thin Films
Authors: Watanabe Takashi , Umesaki Norimasa , Wakita Hisanobu , Onishi Takashi
Published: March 2014

Al-Ta and Al-Nd alloy films are studied by x-ray absorption fine structure (XAFS) spectroscopy, x-ray diffraction (XRD) spectroscopy and the spectral simulations (EXCURV92, Cerius2) in order to make clear the relatinship between the metal content of Ta or Nd, the heat treatment temperature and the structure of intermetallic compounds (e.g. Al3Ta or Al4Nd) in the films. The experimental results indicate that the Al100-xTax (x>11) and/or Al100-yNdy (y>8) alloy films have amorphous structure, and that their intermetallic compounds are in the form of crystallite or quasi-compound structures.
Damaging Effect on K-shell Photoionization Process in InP
Authors: Jin Tao
Published: March 2014

It was studied that radiation effect induced by monochromatic X-rays around K-shell absorption edge of intracrystalline phosphorus or indium in InP. The samples of InP were irradiated by monochromatic synchrotron X-rays above (2.153 or 27.97keV) and below (2.140 or 27.85keV) the K-shell binding energy (BE) of phosphorus or indium. Variation of electronic states on InP [100] surface was analyzed with X-ray photoelectron spectroscopy (XPS). The experimental results showed that the shapes of In3d XPS peak changed little and P2p peak changed greatly, whether the photon absorption of the InP samples occurred at K-shell of phosphorus atom or that of indium. The enhancement effects of K-shell absorption were 4.2×10-6kg C-1 and 3.0×10-5kg C-1 respectively with K-shell photoionization process of phosphorus and indium in InP.
Section Topography in Bragg-case Used for Kinematical Imaging of Microdefects in Si Crystals
Authors: Iida Satoshi , Kitamura Ryuji , Abe Takao , Kawata Hiroshi
Published: March 2014

X-ray topographic study on grown-in microdefects in silicon crystals has been performed. In order to obtain a sharp and high-contrast image of the microdefects, the section topography in the Bragg-case was used and compared with that in the Laue-case. Short wave length synchrotron radiation (0.2A) was used in order to satisfy a condition that the penetration depth of the x-rays was much larger than the extinction distance. Grown-in microdefects in a slowly pulled Czochralski(CZ) grown silicon crystal and in an in situ annealed CZ-Si crystal were investigated. The microdefect images in the section topographs of the Bragg-case were clearer than in those of the Laue-case. This was explained from the fact that, in the Laue-case, defect images overlap with x-ray beams diffracted from nearly perfect regions in the crystal (the Pendellosung fringes), however, they were recorded separately on a photographic plate in the Bragg-case. Besides the strong black contrast of the microdefect images (kinematical images), dynamical diffraction images, x-ray intensity oscillations in tail parts of the defect images, were also observed. The intensity distributions of the dynamical diffraction images of the defects were compared with the dynamical theory of the x-ray diffraction in the perfect crystal in the Bragg-Laue case of type II, and qualitative agreement was obtained.
Inelastic Nuclear Resonant Scattering of FeCl3-Graphite Intercalation Compounds
Authors: Kitao Shinji , Mitsui Takaya , Harami Taikan , Yoda Yoshitaka , Seto Makoto
Published: March 2014

Anisotropic phonon modes of stage-1 FeCl3-graphite intercalation compounds were studied by inelastic nuclear resonant scattering. Partial phonon modes concerning Fe atoms were measured with incident x-rays either parallel or perpendicular to graphite layers. The observed spectra well show the character of the phonon density of state weighted by the projection of phonon polarization vector to the incident x-ray.
Fluorescence EXAFS Study on Local Structures around Bi Atoms in InAs1-xBix Grown by Low-pressure MOVPE
Authors: Ofuchi Hironori , Kubo Toshihiko , Tabuchi Masao , Takeda Yoshikazu , Okamoto Hiroshi , Oe Kunishige
Published: March 2014

We have investigated local structures around Bi in metalorganic-vapor-phase epitaxy (MOVPE)-grown InAs1-xBix (x=0.007, 0.016 and 0.028) by fluorescence extended X-ray absorption fine structure (EXAFS). The EXAFS analysis revealed that even in higher-Bi-concentration InAs1-xBix (x=0.028) the majority of Bi atoms substituted the As sites in the zincblende-type InAs lattice. Obtained Bi-In bond length was 2.81-2.82Å, which was 7% longer than the In-As bond length (2.623Å) in the InAs bulk. Such a long Bi-In bond causes local distortion in the InAs lattice and hence disorder. The degree of the distortion and disorder was observed to increase with the Bi concentration.
Characterisation of Ion-Implantation-Induced Disorder in GaAs by EXAFS
Authors: Glover C. J. , Yu K. M. , Ridgway M. C. , Foran G. J.
Published: March 2014

The Ga and As local atomic environments in ion-implanted GaAs have been characterised with extended x-ray absorption fine structure spectroscopy. The accumulation of disorder prior to the onset of amorphisation has been investigated. For implantation at -188 °C, a heterogenous amorphisation process was identified and an increase in bondlength and Debye-Waller factor and a decrease in first-shell coordination number were observed. Analysis of the EXAFS data using the cumulant method revealed a monotonic increase in asymmetry in the interatomic distance distribution as a function of dose. Amorphised samples implanted to ion doses two orders of magnitude beyond the amorphisation threshold have also been studied and the structural parameters of amorphous GaAs were shown to be independent of implant conditions.
Chemical States of Piled-up Phosphorus and Arsenic Atoms at the SiO2/Si Interface
Authors: Yoshimura Yusuke , Ono Kanta , Fujioka Hiroshi , Hayakawa Shinjiro , Sato Yoshiyuki , Uematsu Masashi , Baba Yuji , Hirose Kazuyuki , Oshima Masaharu
Published: March 2014

We have investigated the positions of the piled-up phosphorus atoms at the SiO2/Si interface using the extended X-ray absorption fine structure (EXAFS) and X-ray photoelectron spectroscopy (XPS). The EXAFS and XPS data can be well explained on the assumption that the piled-up arsenic atoms exist at the tetrahedral sites. On the contrary, phosphorus atoms exist not at the tetrahedral sites but at the denser sites. The depth profile measurements of XPS have revealed that the piled-up arsenic and phosphorus atoms exist within 20Å from the interface.
EXAFS Studies of Liquid Arsenic Chalcogenides
Authors: Miyanaga T. , Hoshino H. , Ikemoto H. , Yamamoto I. , Endo H.
Published: March 2014

EXAFS measurements for liquid As-Se and As-Te mixtures have been carried out on the As, Se and Te K-edges. For liquid As4Te60 it is found by curve fitting analysis that there exist homopolar As-As and Te-Te bonds. This is in contrast with liquid As40Se6 in which the full chemical order is preserved. The coordination numbers around As and chalcogen atoms for both liquid As-Se and As-Te mixtures decrease as temperature increases. At high temperature the network structure formed by threefold coordinated As atoms and two-fold coordinated chalcogen atoms transforms into a chain-like structure, where the semiconducting mixtures show metallic behaviors.
X-ray Absorption Near Edge Structure of Selenium Free Clusters
Authors: Yao Makoto , Hayakawa Tetsuichiro , Nagaya Kiyonobu , Ohmasa Yoshinori , Hamada Koichi , Tai Mitsuharu , Yamamoto Itsuro , Nomura Masaharu
Published: March 2014

Selenium clusters have been produced in the free space and their X-ray Absorption Near Edge Structure (XANES) have been measured in situ on the Se K-edge in the Total-Ion-Yield (TIY) mode by utilizing the beam line BL-12C of Photon Factory in KEK. From the observed TIY intensities, the XANES spectrum of Se dimer and that of larger clusters such as a pentamer have been deduced. The first peak in the XANES spectrum of the Se dimer is smaller and broader than that of the larger clusters, suggesting that the first peak of the dimer is a superposition of the 1s-π* and 1s-σ* bound-state resonances.
Circular Dichroism in Photoemission from Non-Magnetic Materials
Authors: Fecher Gerhard H.
Published: March 2014

Circular dichroism in the angular distribution (CDAD) of photoelectrons is a unique feature appearing if the emission is excited by circularly polarised Synchrotron Radiation. It was first predicted to appear in emission from oriented molecules. Therefore, first experiments on adsorbed molecules have been done in restricted geometries. Later it was found in experiments that the solid surface itself implies the break of symmetry that is needed to observe CDAD in emission from non-magnetic materials. The CDAD in emission from adsorbates or surfaces is a direct consequence of photoelectron diffraction. The distribution of the CDAD in the hemisphere above the sample can be interpreted as hologram. It will be shown how this type of dichroic hologram can be used to reconstruct the real space distribution of the atoms in a solid, or in an adsorbate - substrate system. Different elements can be identified in compounds or alloys due to the elemental sensitivity of X-ray photoemission. As further application it will be shown how CDAD can be used in photoemission microscopy as a contrast giving mechanism.
XAFS Investigation of Mercury Sorption on Carbon-based and Other Sorbent Materials
Authors: Huggins Frank E. , Yap Nora , Huffman Gerald P.
Published: March 2014

The sorption of mercury from simulated coal combustion flue gases on coal-derived chars, activated carbons, and zeolites has been examined using mercury LIII XAFS spectroscopy. The energy difference between the two inflection points (IPD) in the mercury XANES spectra has been shown to be a sensitive indicator of the local structure around the mercury adsorbed on the sorbent. The value of the IPD appears to reflect the form of mercury added to the flue gas and to be sensitive to acidic gaseous species such as HCl and H2SO4 that may be present in the flue gas, whether from addition to the flue gas or from the sulfur and chlorine in the coal. The data suggest that well-defined mercury species are not formed on carbon-based sorbents, but rather the structure and chemistry of the sorbed mercury species reflect the different anionic species present in the flue gas, as well as any activating element on the sorbent itself.
XAFS Study on the Structure of Ytterbium(III) Trifluoromethanesulfonates as a New Type Catalyst
Authors: Yoshida Tomoko , Tanaka Tsunehiro , Yamamoto Takashi , Yoshida Satohiro , Ishitani Harurou , Kobayashi Shu
Published: March 2014

Yb L3-edge XAFS spectroscopy was applied to study on the local structures around Yb atoms in ytterbium(III) trifluoromethanesulfonates (Yb(OTf)3) catalysts dissolved in various solution and those in Yb(OTf)3 chiral catalysts prepared by a choice of two types of achiral ligands. XAFS analyses showed the difference in the coordination number of oxygen atoms between Yb(OTf)3 catalysts dissolved in aqueous and nonaqueous solutions, suggesting the activation of the Yb(OTf)3 catalyst by the hydration. For the two Yb(OTf)3 chiral catalysts, both the catalysts were found to be present as trivalent ytterbium oligomer. Curve-fitting analysis of EXAFS showed that the Yb-Yb distance of two catalyst complexes is fairly different from each other, i.e., one is 3.68 Å and the other 4.04 Å, which is expected to explain the difference of the catalytic performance of the two chiral catalysts.
Resonant Inelastic X-Ray Scattering in Ni Componds
Authors: Shoji Hironobu , Kobayashi Kenji , Iwazumi Toshiaki , Katano Rintaro , Isozumi Yasuhito , Kisnimoto Shunji , Nanao Susumu
Published: March 2014

Resonant inelastic x-ray scattering was measured at the Ni K-edge in NiO, NiSO4, NiF2, NiCl2 and NiBr2. The charge-transfer energies from a ligand field to the Ni 3d states of these compounds are obtained directly from the energy differences between the elastic and the 4p→1s inelastic scattering. The sample dependence of the energy shift agrees roughly with the result of a fitting calculation of the 2p-x-ray photoelectron spectroscopy. We observed a negative correlation between the energy shift and the intensity ratio of the shoulder to the main peak of the Ni Kβ1,3 emission spectra. Because this spectral ratio refers to the number of 3d electrons, the charge-transfer to the 3d states is depressed with increasing charge-transfer energy.
Sulfur Behavior in Rapid Pyrolysis of Coals with Chemical Pretreatments
Authors: Sugawara Katsuyasu , Sugawara Takuo , Shirai Masayuki
Published: March 2014

Lignite, subbituminous, and bituminous coals were pyrolyzed rapidly in a free-fall reactor under a nitrogen stream at 1253 K in order to clarify pyrolysis desulfurization behavior. Chemical pretreatments were carried out to search the efficient desulfurization. X-ray absorption near edge structure (XANES) was applied to the direct determination of the sulfur forms. XANES analysis indicated that lignite contained disulfide, which could contribute to the high extent of organic sulfur removal. Sulfone and sulfoxide formed by the pretreatments might also contribute to efficient desulfurization.
Characterization of Diamond Single Crystals for Synchrotron Radiation Monochromators
Authors: Tsusaka Yoshiyuki , Takeda Shingo , Takai Kengo , Yokoyama Kazushi , Kagoshima Yasushi , Matsui Junji , Sato Shuichi , Toda Naohiro , Kimura Shigeru
Published: March 2014

The diamond crystals with a (100) or a (111) surface are characterized by the uses of rocking curve measurements, reciprocal lattice mapping and Lang topography method. The full widths at the half maxima of the rocking curves at the X-ray energy of 8.04 keV have been measured to be 6.5 arcsec and 6.3 arcsec for 400 and 111 Bragg reflection, respectively. While the value for 400 reflection is 1.3 times larger than the theoretical value, that for 111 reflection is almost the same as the theoretical one. A sub-peak of about 15 arcsec leaning to the main peak is clearly seen in the reciprocal lattice maps of (100) crystals. No sub-peak can be seen in those of (111) crystal. In addition, some streaky intensity distribution due to a dynamical effect of the X-ray diffraction, being elongated in the radial direction from the reflection point, is clearly seen. This means that crystallinity of (111) planes is more perfect. From the (100) Lang's topographs, it has also been clarified that the diamond crystals include some defect bundles inside the crystals.
Multiple-Energy X-ray Holography with Atomic Resolution
Authors: Gog Thomas
Published: March 2014

Multiple-energy x-ray holography (MEXH) is a particular implementation of an x-ray holographic method capable of directly imaging atomic structures in the bulk, at surfaces and interfaces of solids. It utilizes an interference field generated by incident and scattered x-rays within the sample, then determines its strength at specific atomic sites from integral fluorescence yields. Scanning large portions of reciprocal space, a hologram is recorded, which can be converted to a real space image by Fourier transformation. Image aberrations that adversely affect results in single-energy techniques are successfully avoided in this novel multi-energy version.