bluuebunny/crossref_metadata_2025 huggingface dataset:
Site Specific Photochemical Reaction of PMMA by Core Electron Excitation
Authors: Ueno N. , Komada M. , Morimoto Y. , Tinone M. C. K. , Kushda M. , Sugita K. , Honma K. , Tanaka K.
Published: March 2014

The photon energy dependence of photoion emission from solid films of poly(methyl methacrylate) was measured to investigate the primary steps in radiation induced decomposition following carbon and oxygen 1s electron excitations using monochromatic pulsed-synchrotron radiation. Various ions including the monomer ion were observed. Further it was clearly found that the decomposition depends on the nature of the electronic states created in the excitation process. Excitations of carbon 1s electrons to π* and σ* resonance states at 287.9 eV show remarkable enhancement of the ion emission for CH+ and CH2
+. In the energy region of oxygen 1s electron excitation, the increase of COOCH3
+ ion was not observed due to a fragmentation of the side chain by creating oxygen 1s hole.
DV-Xα Molecular Orbital Method for X-ray Absorption Near Edge Structure–Application to N2 and CrO4
2-
Authors: Nakamatsu Hirohide , Mukoyama Takeshi , Adachi Hirohiko
Published: March 2014

We have performed DV-Xα molecular orbital calculations for XANES of the N2 and CrO4
2- species to confirm our conclusions concerning the origin of shape resonances reported before. The theoretical spectra in the present work are in good agreement with the experimental spectra. Shape resonances for the N2 molecule are examined and, as well as the previous works, found to-be due to electron scattering by the attractive potential of molecule, neither due to centrifugal barrier nor another potential barrier.
XAFS Applied to Trace Element Analysis
Authors: Nomura Masaharu
Published: March 2014

The sensitivity of X-ray Absorption Edge Spectrometry has been improved by using synchrotron radiation as the light source and analytical method developed for EXAFS. Qualitative as well as quantitative information is obtained free from any interferences which are experienced in many physicochemical methods. This method does not need any empirical information except the thickness of sample cell and is nondestructive. Excellent linearity is shown on Ag-Cd (200 to 1 ppm Cd in 1000 ppm Ag). Minimum detection limit is 0.5 ppm for cadmium and no limitation for maximum concentration. This report also stress the importance of careful inspection of χ(k) data when analyzing EXAFS.
High Brilliance Beamline for Time Resolved X-ray Absorption Spectroscopy at ESRF
Authors: Hagelstein Michael , Fontaine Alain , Goulon José
Published: March 2014

Beamline 8 at the ESRF equipped with a low K undulator, coupling x-ray optics and an energy dispersive XAFS spectrometer is under construction and shall be in operation by 1995. Undulator gap tuning and tapering the magnetic field by a linear variation of the undulator gap will be provided to choose the spectral characteristics for experiments at defined absorption edges. A flux of 1012 photons per second on the sample within the total spectral range of 5 keV to 25 keV and a time resolution below 100 microseconds shall be reached. Small sample volumes can also be analyzed due to the high brilliance of the generated synchrotron radiation.
Sensitivity of Spectrometers and Optical Components to Floor Instability and Vibrations
Authors: Goulon José , Brookes Nicholas B. , Vettiher Christian
Published: March 2014

For the third generation of low emittance storage rings and high brilliance sources, one should not underestimate the troubles that can be caused by short (or long ) term instrumental instabilities, mechanical resonances, ground vibrations and local excitation of unwanted noise of any type. It is shown that the “Dragon” type spectrometer which we plan to install on the low energy side-branch of the ESRF BL#6 is critically sensitive to differential and angular instabilities which may cause a significant deterioration of the energy resolution unless the rms amplitude of vertical displacements is kept below : σδz (rms) ≤ 0.125 µm. Intensity fluctuations could also prevent us from detecting minute circular dichroism effects. In this perspective, we comment briefly the results of low frequency vibration test measurements carried out on repaired slabs in the ESRF Experimental Hall. Although the site stability is not quite as good as expected on the basis of the most optimistic reports, vibration noise should not have any dramatic consequence on the operation of the Spectroscopy BL#6, unless the slab repair deteriorates with time.
Comparison between XAS, AWAXS and DAFS Applied to Nanometer Scale Supported Metallic Clusters: Part II Bimetallic Clusters
Authors: Bazin Dominique , Sayers Dale
Published: March 2014

The structural information obtained using three techniques related to synchrotron radiation are compared. XAS (X-ray Absorption Spectroscopy), AWAXS (Anomalous Wide Angle X-ray Scattering) and DAFS (Diffraction Anomalous Fine Structure) are applied to the study of nanometer scale bimetallic clusters.
A Laboratory Scale Apparatus for the Time-Resolved X-ray Absorption Spectroscopy Using Laser Plasmas as an X-ray Source
Authors: Yoda Osamu , Miyashita Atsumi , Murakami Kouichi , Ohyanagi Takasumi , Aoki Sadao , Yamaguchi Naohiro
Published: March 2014

A time-resolved X-ray absorption spectroscopy apparatus in the laboratory scale has been set-up which utilizes laser plasmas as a soft X-ray source. One of the major objectives using this apparatus is to observe X-ray absorption fine structures (XAFS) of various materials during materials processing in an energy region between 100eV and 3keV. For this purpose, we have provided two sets of optical and detecting systems, i.e., a toroidal mirror, grazing incidence flat-field grating and MCP for lower energy region (100-1000eV), and a toroidal mirror, curved KAP crystal and MCP for higher energy region (1-3keV). The most intense X-rays are generated from Au plasma and the intensity reaches as high as 1016 photons/pulse in 2π steradian in the energy region below 300eV. In this case, the conversion efficiency of the laser energy to X-rays is 4.6%. The energy resolution of the spectrometer ΔE/E has been found to be 5×10-3. We show some examples of XAFS measurements on carbon during laser ablation.
Detection Limits for Natural Circular Dichroism of Chiral Complexes in the X-ray Range
Authors: Goulon José , Sette Francesco , Moise Claude , Fontaine Alain , Perey Dantele , Rudolf Petra , Baudelet Francois
Published: March 2014

Whereas both Magnetic Circular Dichroism and Faraday Rotation studies have been successfully carried out at the K-, L- and M-absorption edges of metal atoms in ferromagnetic systems, Natural optical activity of chiral complexes has not yet been detected quite unambiguously in the X-ray range. We review a number of theoretical arguments which confirm that the optical asymmetry factor gσ should be very small in the X-ray range for unoriented powdered samples, especially at the K-absorption edges. This stimulating challenge prompted us to start an intensive programme of measurements aimed at detecting natural circular dichroism in both the soft and “firm” X-ray ranges. Although some of our experiments look consistent with the presence of the expected effect, our conclusions cannot be taken yet as definitive due to the presence of a weak residual signal which, unfortunately, could not be eliminated.
Multiple Scattering Contributions at the L1 and L3 Barium EXAFS Spectra in Barium Fluoride
Authors: Chaboy Jesus , Garcia Joaquín , Marcelli Augusto
Published: March 2014

In this paper we present a detailed analysis of the barium L3 and L1 EXAFS spectra of barium fluoride at 10 K and room temperature. Single and multiple scattering contributions have been calculated in the frame of the multiple scattering theory for a cluster including up to eleven shells using the Hedin-Lundqvist complex potential. The results show that the L1 and L3 EXAFS spectra.can be well reproduced only if X3 and X4 multiple scattering contributions are included.
X-Ray Magnetic Circular Dichroism and XANES Spectra at Pt L2,3-edges in Fe–Pt Alloys
Authors: Maruyama Hiroshi , Koizumi Akihisa , Kobayashi Kenji , Yamazaki Hitoshi
Published: March 2014

X-ray magnetic circular dichroism and X-ray absorption near-edge structure have been measured at the Pt L
2,3-edges of Fe-Pt alloys in ordered and disordered phases. The intensity ratio between these spectra at the L
2- and L
3-edges substantially deviates from the predicted values, which indicating that orbital angular momentum exists on the unoccupied 5d-states of Pt atom. The orbital angular momentum calculated by new magneto-optical sum rule is compared with the results of band calculation.
XAFS of Tb.27Dy.73Fe1.95 as a Function of Magnetic Field
Authors: Bonin Y. R. , Crozier E. D.
Published: March 2014

Magnetostriction refers to the change in length of a ferromagnetic material when a magnetic field is applied. The largest known rnagnetostrictive effect occurs in the rare earth alloys, Tb1-x
Dy
x
Fe2. In fully magnetized Tb.27Dy.7Fe1.95 (Terfenol-D) the strain is Δ
l/l=1.2×10-3. Technologically, this material is an important candidate for various transducers. The aim of the present EXAFS study was to reveal the structural changes that occur when a magnetic field is applied. The Terfenol-D sample was a twinned crystal with growth axis along the <112̄> direction. The greatest magnetostriction occurs when the field is applied in the <111> direction, perpendicular to the growth axis and the <11̄0> direction. The thickness of the sample prevented the use of transmission or fluorescence techniques to measure the x-ray absorption fine structure (XAFS). Thus an electron yield detector was designed and built to fit between the poles of the magnet, which were only separated by 8.9mm. Magnetic fields up to 4800 Oersted were applied in the <111> direction. In this paper results for a polarization-dependent XAFS measurements at the Fe K edge to examine the atomic displacements parallel and perpendicular to the applied field are presented.
Ab-initio XAFS Calculation for a-As2S3
Authors: Pfeiffer G. , Rehr J. J. , Sayers D. E.
Published: March 2014

Ab initio calculations of the As K-edge XAFS of a-As2S3, encompassing both XANES and EXAFS, were performed using a curved-wave multiple-scattering (MS) approach applied to an atomic cluster representing the amorphous solid. The XAFS function obtained this way is combined with the calculated absorption cross section to simulate the experimental absorption spectrum. The experimental absorption edge structure is resolved into two components, one representing a bound excited state resonance and the second due to transitions to the continuum. The bound state resonance, represented by a Lorentzian, is located about 5.3 eV below the continuum threshold which in turn is simulated by an arctan function. The continuum structure is computed using χ and cross section data.
X-ray Resonance Exchange Scattering Study of Nd2Fe14B
Authors: Koizumi Akihisa , Namikawa Kazumichi , Maruyama Hiroshi , Mori Koichi , Yamazaki Hitoshi
Published: March 2014

The X-ray resonance exchange scattering (XRES) has been measured at the Nd L
2,3-edges on the 330, 440 and 550 Bragg reflections in a ferromagnetic Nd2Fe14B single crystal. The XRES results at the L
2-edge reflect the spin polarization of unoccupied 5d-bands of Nd due to electric dipole transitions. Those at the L
3-edge show the possibility of electric quadrupole transitions to the highly localized 4f-states. The temperature dependence of XRES confirms the sensitivity to the local magnetic moment of specific site. The magnetic moments of Nd 4f and 4g sites rotate from the c-axis with different angles below spin reorientation temperature.
Multiple Scattering Approach to the XANES of Co Amine Complexes
Authors: Akai Toshio , Koike Yasuo , Yimagawa Masaru , Fujikawa Takashi
Published: March 2014

The short-range order multiple scattering calculation is carried out for the Co K-edge XANES spectra of a new divalent complex N-N'-bis(3-aminopropyl)-1,3 propandiamine Co(II) complex (Co-APPD) and a reference trivalent complex [Co(NH3)6]Cl3. The calculated spectra are in good agreement with the experimental ones when we use the appropriate electron configurations of Co and N atoms for the phase shift calculation.
Adsorption of Thiophene on Ni(100) Studied by S K-edge XANES
Authors: Takata Yasutaka , Kitajima Yoshinori , Aga Hiroji , Yagi Shinya , Asahi Toshiyuki , Yokoyama Toshihiko , Tanaka Kenichiro , Ohta Toshiaki
Published: March 2014

Adsorption behavior of thiophene (C4H4S) molecule on clean and oxygen-precovered Ni(100) surface at ∼90K has been studied by polarization dependent S K-edge XANES. S1s→π* and σ*(S-C) transitions were symmetrically resolved in the polarizaton-dependent XANES spectra of the molecule with a specific orientation on O-precovered Ni(100), which could not be separated and assigned unambiguously in the spectrum of gaseous molecule. From the polarization dependence of those peaks, it is revealed that the C4H4S molecule does not decompose and lies nearly parallel to the surface on both clean and Oprecovered Ni(100) surface. Comparing the present results with those of thiophenol and carbon disulfide, interaction between adsorbed molecules and substrate metal is discussed.
Adsorption of CS2 on O-, S-, and C-Precovered Ni(100) Studied by S K-edge XANES
Authors: Yagi Shinya , Takata Yasutaka , Kitajima Yoshinori , Asahi Toshiyuki , Aga Hiroji , Yokoyama Toshihiko , Ohta Toshiaki
Published: March 2014

Adsorption behavior of CS2 molecule on O-, S- and C-precovered Ni(100) surfaces has been studied by polarization dependent S K-edge XANES. The adsorption behavior changes significantly with the precovered elements of O, S and C, though the adsorption site and coverage are the same; CS2 molecule does not dissociate on O- or S-precovered surface at 100K and lies nearly parallel to the surface even in the multilayer, and does dissociate on C-precovered surface. Both the electronic and geometric effects of precovered elements on the inhibition of dissociation are discussed.
Surface Structure of Low Coverage Chlorine Adsorbed on a Nickel Stepped Surface
Authors: Ishii Hideshi , Asakura Kiyotaka , Ohta Toshiaki , Kitajima Yoshinori , Kuroda Haruo
Published: March 2014

The surface structure of Cl/Ni(7 9 11) was studied by means of SEXAFS. At the initial stage of chemisorption (∼0.1 ML), chlorine atoms adsorb mainly on the terrace 3-fold site in contrast to sulfur and phosphorus on Ni(7 9 11), where the adsorption on the step 4-fold site is predominant.
Multiple Scattering Cluster Approach to Oxygen and Carbon K-shell NEXAFS Spectra of HCOO-Cu(110)
Authors: Tang J. C. , Feng X. S.
Published: March 2014

We have calculated the oxygen and carbon K-shell near-edge X-ray absorption fine structure (NEXAFS) spectra of formate (HCOO) adsorbed on Cu(110) surface in terms of the multiple-scattering cluster method. The calculation shows that the molecular bond-length L
C-O
=1.26±0.01Å,the adsorption distance of oxygen L
O-C
u
=1.99±0.04Å. We have found the C-H resonance existing in the carbon K-shell NEXAFS spectra. The origin of the C-H resonance has been discussed.
Interfacial Reaction in a-Si/Au and a-Si/Cu Thin Film Bilayers
Authors: Heald Steve M. , Tan Zhengquan
Published: March 2014

We have studied the interdiffusion and compound formation at the a-Si/Au and a-Si/Cu thin film interfaces using x-ray reflectivity and grazing incidence EXAFS techniques. In the 0 °C as-deposited samples, reaction between Si and Au is minimal, but reaction between Si and Cu is significant. Upon annealing for ten minutes in argon, the a-Si crystallized and reacted quite extensively with Au at 160 °C. Further reaction between Si and Cu proceeded at 130 °C. The compounds formed appear to be metal-rich silicides in both the Si/Au and Si/Cu systems. For Au/Si the silicide is likely stabilized on the surface of the newly formed crystallites.
X-ray Absorption Study of the Reaction of Zirconium Thin Films on Silicon(111)
Authors: Dao Y. , Edwards A. M. , Nemanich R. J. , Sayers D. E.
Published: March 2014

X-ray absorption measurements of 100Å Zr thin films deposited on Si(111) substrates in UHV have been obtained by using a total electron yield detector. Experiments were performed on Zr/Si thin films in order to obtain structural information and find the optimum annealing temperature to produce uniform ZrSi2 epitaxial thin films on Si(111) substrates. A quantitative X-ray absorption fine structure analysis indicates that the films annealed above 650°C form ZiSi2 disilicides, which have the orthorhombic-base centered C49 structure.
Electron Yield XAFS Study of Evaporated Co/Pd Multilayers with Various Thickness Ratios of Co to Pd Sublayers: Simulations of the Co K-edge XAFS and Fourier Transforms
Authors: Choi M. , Joo J. H. , Kim S. K. , Kang J. S. , Lee Y.-P. , Shin S.-C. , Heald S. M.
Published: March 2014

Electron-yield XAFS measurements were made on e-beam evaporated Co/Pd multilayers with various sublayer thicknesses and different thickness ratios of Co to Pd sublayers. The Co K-edge and the Pd K-edge XAFS data were obtained for the Co/Pd multilayers with the sublayer thicknesses of 3Å/4Å, 15Å/4Å, 3Å/15Å, 2.1Å/13.5Å, and 2.2Å/4.5Å. The Fourier transforms of the Co K XAFS for most samples show a splitting of major peak, and the magnitude ratio of these split peaks varies systematically with the thickness ratio of the Pd sublayer to the Co sublayer, whereas the Fourier transforms of the Pd K XAFS for the same samples do not show a splitting of peaks. As a preliminary analysis, the Co K XAFS and the split peaks in the Fourier transform for the Co/Pd(3Å/4Å) case were simulated by using the FEFF calculations, and the Co K XAFS and the major peak in the fourier transform for the Co/Pd(15Å/4Å) case were also simulated consistently.
Polarized Total-Reflection Fluorescence EXAFS Studies on Asymmetric Surface Structures of Catalysts
Authors: Shirai Masayuki , Asakura Kiyotaka , Iwasawa Yasuhiro
Published: March 2014

Asymmetric structures of active metal oxides (Cu oxide, Co oxide) on single crystal surfaces were determined by polarized total-reflection fluorescence XAFS spectroscopy (PTRF-XAFS). An asymmetric particle structure (or growth mode) of small spinel-like Co3O4 was directly demonstrated by this method.
Glancing Angle EXAFS Investigation of InGaAs/GaAs Strained Layer Multiple Quantum Wells: Strain and Bond Distances
Authors: Turchini Stefano , Proietti M. Grazia , Martelli Faustino , Alagna Lucilla , Bruni M. Rita , Prosperi Tommaso , Simeone M. Gabriella , Garcia Joaquin
Published: March 2014

The strain distribution in quantum wells of InxGa1-xAs/GaAs (x<0.25) is investigated by glancing-angle EXAFS. The measures have been performed at glancing angles below the critical angle for total reflection in order to avoid substrate contributions to the signal.
The results show that a number of Ga-As bond lengths are stretched. Indeed, two Ga-As bonds distances coexist: 2.43±0.01 Å and 2.62±0.04 Å, which correspond to the Ga-As and In-As bond distances in the binary compounds GaAs and InAs, respectively. This result is independent of the In molar fraction in the strained alloy layers.
In-situ Study of an Underpotential-Deposited Cu Layer on Pt
Authors: Pant J. , Pansewicz K. , Zhang J. , Hayes T. M. , Wang L. , Furtak T. E.
Published: March 2014

We have performed in-situ fluorescence-detection x-ray absorption spectroscopy studies of the Cu environment in a layer of Cu deposited electrochemically on a large polycrystalline Pt electrode. We report spectra acquired with x-ray electric field vector parallel and perpendicular to the surface. This is the first time that these two measurements have been done on the same layer.
Application of X-ray Absorption Near-Edge Spectroscopy at the S K-edge to the Structural Characterisation of Surface Reacted Metallic Alloys
Authors: Crabb T. A. , Roberts K. J. , Gibson P. N.
Published: March 2014

X-ray absorption spectroscopy has been used to study the interaction of H2S at 700°C with a protective oxide layer on a Ni-20Cr alloy. Both fluoresence and electron yield detection modes, applied simultaneously, enabled structural information from 100nm and 5nm respectively to be probed which allowed the processes at the air/oxide and oxide/alloy interfaces to be monitored as a function of corrosion time. The data revealed sulphur to be in a high 6+ oxidation state in the early stages of the corrosion process, changing to 2- with the formation of a thicker sulphide-like surface film.
XANES Spectroscopic Studies of Merocyanine Dyes and Their Adsorbed States on AgCl
Authors: Araki Tohru , Seki Kazuhiko , Narioka Satoru , Takata Yasutaka , Yokoyama Toshihiko , Ohta Toshiaki , Watanabe Satoko , Tani Tadaaki
Published: March 2014

We studied the sulfur K-edge XANES spectra of several merocyanine dyes and an antifoggant PMTZ (phenylmercaptotetrazole) in the form of neat powder and adsorbed state on AgCl. Reflecting the localized nature of core excitations, the spectra of merocyanine dyes can be interpreted as contributions from S atoms in three chemical environments. The spectra of these dyes adsorbed on AgCl show significant change when S atom is in the thione (=S) form, while little change was observed when S is in the thia (-S-) form in the aromatic ring. This indicates that the dye in the thione form is adsorbed at the C=S group, while the dye with thia form may be adsorbed at other site than S. The deposition of PMTZ on AgCl also caused significant spectral change, which corresponds to the strong interaction of PMTZ with AgCl at the S site.
The Structure of Well Defined SiO2 Supported MoO3 Clusters during Sulfidation. An in situ EXAFS-study
Authors: Boer Mark De , Dillen A. Jos Van , Koningsberger Diek C. , Geus John W.
Published: March 2014

The sulfidation of a well defined MoC3/SiO2 catalyst has been examined by means of TPS, EXAFS, and TEM. The oxidic clusters in a 5.6 wt% MoO3/SiO2 catalyst are transformed into almost completely sulfided particles (MoOxSy) by O-S exchange at RT. A molybdenum-sulfido particle that resembles the MoS3 structure is formed during sulfidation at 423 K. The MoS2 phase is formed at temperatures between 523 and 573 K. The transition of MoS3 into MoS2 can be monitored by evolution of H2S from the catalyst, with simultaneous consumption of H2. The twodimensional size of the MoS2 slabs can be derived from the EXAFS Mo-Mo coordination number by means of a theoretical model. The stacking height of the slabs must be elucidated by TEM.
Decomposition of Molybdenum Hexacarbonyl Deposited on Dehydroxylated Alumina
Authors: Lee Jae Sung , Boudart Michel
Published: March 2014

Deposition and decomposition of Mo(CO)6 on dehydroxylated alumina was studied by XAFS. The rate of deposition and the structure of deposited species depended on deposition temperature. In the deposition at 320 K, the rate was slow and the species on the support was found to be Mo(CO)5. The species formed at 360 K had an average stoichiometry of Mo(CO)2.5 without well-defined structure. Heating of the deposited subcarbonyls in flowing H
2 caused first simple decarbonylation and then methanation above 450 K. Around 930 K, highly carbon deficient Mo
2
C was formed which was converted to metallic Mo upon further heating to 970 K.
A New Fast Spherical Approximation (FSA) for Calculation of Multiple-Scattering Contributions in XAFS
Authors: Kuzmin Alexei , Purans Juris
Published: March 2014

A new Fast Spherical Approximation (FSA) for the calculation of the multiple-scattering contributions in the X-ray-absorption fine structure is suggested. The analysis of the XAFS-spectra of the Re L
3-edge in ReO3, the W L
3-edge in NaWO3, the Ir L
3-edge in IrO2 and the Mo K-edge in MoO3 is considered. It is shown that the theoretical spectra, calculated using the FSA, are in good agreement with the experimental data both in the low and high energy ranges.
EXAFS and XANES on Ti-Containing Zeolite Y
Authors: Schultz E. , Ferrini C. , Prins R.
Published: March 2014

X-ray absorption experiments were carried out on titanium containing zeolites. The edge- and EXAFS-regions proved that the Ti-sites in TS-1 and [Ti]ZSM-5 are similar and well separated from each other. In contrast, EXAFS analysis of a [Li,Ti]Y zeolite, containing 12 % Ti, showed that small rutile-like TiO2 particles are present in this zeolite, probably in the supercages of the faujasite structure.
EXAFS and XANES Investigation of the Structure of TiCl4 and TiCl4-Filodiene Reaction Intermediates in Solution
Authors: Sanchez M. Concepción , Garcia Joaquín , Mayoral Jose Antonio , Proietti M. Grazia , Chaboy Jesus , Ruiz-Lopez Manuel. F.
Published: March 2014

The local structure around TiCl4 and TiCl4- -Filodiene compexes in solution has been studied by means of x-ray absorption spectroscopy. Analysis of the EXAFS spectra shows that TiCl4 coordinate to two oxygen atoms belonging to the organic counterpart Theoretical XANES spectra have been calculated and compared with the experimental data and the features present in the spectra interpreted in terms of multiple scattering contributions.
A Structural Model for the Photosynthetic Oxygen Evolving Manganese Complex
Authors: Yachandra V. K. , DeRose V. J. , Latimer M. J. , Mukerji I. , Sauer K. , Klein M. P.
Published: March 2014

EXAFS and XANES spectra of photosystem II preparations from spinach and Synechococcus in the S1 and S2 states are presented. The structure, oxidation state, and the role of the cofactors calcium and chloride are discussed. A structural model for the Mn complex in photosystem II is proposed.
Characterization of the Mn Site in the Photosynthetic Oxygen Evolving Complex: The Effect of Hydroxylamine and Hydroquinone on the X-ray Absorption Spectra
Authors: Riggs Pamela J. , Mei Rui , Yocum Charles F. , Penner-Hahn James E.
Published: March 2014

X-ray absorption spectroscopy has been used to characterize the Mn site in the photosynthetic oxygen evolving complex (OEC) reaction center core complex. Treatment in the dark with hydroxylamine or with dihydroquinone results in a shift of the XANES spectra to lower energy, consistent with reduction at the Mn site. Structural changes are seen in the EXAFS as well. In both cases, the structural changes are completely reversible on illumination.
Mn K-edge XANES Spectroscopy of Photosynthetic Water Oxidation Enzyme in the S0-, S1-, S2- and S3-States Induced by Flash Excitation
Authors: Ono Taka-aki , Noguchi Takumi , Inoue Yorinao , Kusunoki Masami , Matsushita Tadashi , Oyanagi Hiroyuki
Published: March 2014

Electronic and structural rearrangement of the Mn-cluster during the four step oxidation of water in photosynthetic oxygen evolution was studied by XANES spectroscopy. The Mn K-edge energy of the spectrum was changed with flash number to show a clear quadruple oscillation, indicating a periodic change in oxidation and electronic state of the Mn-cluster depending on Joliot and Kok's oxygen clock.
Rapid-Freeze XAFS Characterization of Kinetic Intermediates of Metalloproteins
Authors: Saigo Satoshi , Hashimoto Hideki , Shibayama Naoya , Nomura Masaharu , Nagamura Toshihiko
Published: March 2014

The reaction of cyanomet myoglobin (Mb+CN-) with dithionite follows biphasic kinetics with formation of an unstable intermediate, supposed to be cyanide-bound ferrous myoglobin. The Fe K-edge X-ray absorption spectrum of the intermediate has been measured by using newly-developed rapid-freezing apparatus and compared with the spectra of Mb+CN- and deoxy myoglobin (Mb). Except for changes in the preedge peaks and a shift of the edge position, no significant changes are observed between the XANES spectra of Mb+CN- and the intermediate. This indicates that CN- remains bound linearly in the intermediate similarly as in Mb+CN-. The EXAFS of the intermediate is almost identical to that of Mb+CN- but different from that of deoxy Mb. Analysis of the EXAFS has shown that the average iron-nearest neighbor atom distance is 1.99±0.01 Å for both Mb+CN- and the intermediate and 2.05±0.01 Å for deoxy Mb. These results show that the local structure around the heme iron does not change upon reduction until the cyanide ligand is released.
XANES Study of the Modified Myoglobin with Distal N-tetrazolylhistidine E7
Authors: Kato Minoru , Iwata Takashi , Iizuka Tetsutaro , Oyanagi Hiroyuki , Shiro Yoshitsugu
Published: March 2014

Tetrazole-myoglobin (Tet-Mb), which is the chemically modified myoglobin having distal N-tetrazolylhistidine E7, exhibited physically and biologically unique properties1,2. We have measured XANES spectra for carboxyforms of Tet-Mb and native Mb by using Synchrotron Radiation of Photon Factory (Tsukuba) to investigate the local structure around the heme iron. The features at the fine structure termed C1 and D show that the Fe-C-O angle increases by the chemical modification. Infrared spectra of the CO stretching mode of Tet-MbCO support this result. The structure and function of Tet-Mb are discussed on the basis of the spectroscopic results.
XAS Study of the Heme Iron Coordination in HIS64(E7)TYR Synthetic Sperm Whale Myoglobin
Authors: Cortes Robert , Ascone Isabella , Pin Serge , Alpert Bernard , Chiu Mark L. , Sligar Stephen G.
Published: March 2014

By using site-directed mutagenesis of the synthetic sperm whale myoglobin, the native distal histidine residue, at position 64 (the helical position E7), was substituted with a tyrosine. The heme iron coordination in wild-type myoglobin and in His(E7)Tyr mutant was studied by X-ray Absorption Spectroscopy (XANES and EXAFS). Data show that the iron is bound to the OH group of tyrosine.
XAS Study of the Copper Glutathione and of Its Interaction with Copper-Free, Zn Superoxide Dismutase
Authors: Ascone Isabella , Longo Antonella , Dexpert Hervé , Rotilio Giuseppe , Desideri Alessandro
Published: March 2014

The reconstitution of Cu,Zn superoxide dismutase from the copper-free protein and Cu(I) GSH complex has been studied by X-ray absorption spectroscopy. The results indicate a direct transfer of the copper as Cu(I) from the GSH complex into the native copper site of the protein. The copper is then slowly oxidized to give the spectrum typical of the Cu(II),Zn(II) protein.
Full Multiple-Scattering Approach to K-Edge XANES of SeTe Mixture
Authors: Yimagawa Masaru , Fujikawa Takashi , Miyanaga Takafumi
Published: March 2014

The Se K-edge XANES spectra of SeTe mixture are studied by use of a full multiple-scattering approach. We calculate the Se K-edge XANES of Se50Te50 mixture crystal, in particular we study various atomic arrangements in the spiral chains. As a result of the comparison between these calculated and experimental spectra, we can grasp an image of the substitution in these mixtures; the homogeneously mixed model, –SeTeSeTe– is ruled out.
A Structural Model for the Soybean Lipoxygenase-1 Iron Site
Authors: Heijdt Lambertus M. van Der , Guillot-Edelheit Geneviève , Mulliez Etienne , Navaratnam Suppiah , Feiters Martinus C. , Nolting Hans-Friedrich , Hermes Christoph , Veldink Gerrit A. , Vliegenthart Johannes F. G. , Chottard Jean-Claude
Published: March 2014

In this communication the striking similarity between the EXAFS of soybean lipoxygenase-1 and that of a methanol-solution of a well-characterized iron-polyimidazole model compound is reported. This similarity is a strong corroboration of the structure proposed earlier for the non-heme iron active site in lipoxygenase (S. Navaratnam, M.C. Feiters, M. Al-Hakim, J.C. Allen, G.A. Veldink, J.F.G. Vliegenthart, Biochim. Biophys. Acta, 1988, 956, 70)
XAFS Studies of Vanadium in the Polychaete Worm Pseudopotamilla Occelata, a New Vanadium Accumulator
Authors: Nakai Izumi , Numako Chiya , Okoshi Kenji , Ishii Toshiaki
Published: March 2014

High accumulation of vanadium in P. occelata was recently discovered by the authors. The animal is a polychaete worm living in a clean sea and is the second vanadium accumulator in the Animal Kingdom, the ascidians being the first. XAFS analysis of the living animal disclosed that the vanadium was present as V(III) ions in a highly symmetrical octahedral coordination environment. This low oxidation state was stable only in a living state and it was easily oxidized in air to the V(IV) state if the sample was homogenized in an agate mortar or it was dried.
The Local Structure of High-Temperature Superconductors
Authors: Leon José Mustre De , Conradson Steven D. , Bishop Alan R. , Raistrick Ian D.
Published: March 2014

We show how XAFS has been successfully used in the determination of the local crystal structure of high-temperature superconductors, with advantages over traditional diffraction techniques. We review the experimental results that yielded the first evidence for an axial-oxygen-centered lattice instability connected with the superconductivity transition. The interpretation of this instability in terms of a dynamical tunneling model suggests the presence of polarons in these materials. XAFS on Tl2Ba2CuO6 and other Tl-based superconductors indicate the presence of local instabilities in the CuO2 planes of these materials, in addition to axial-oxygen instabilities.
Polarization-Dependent EXAFS Study on Superconducting YBa2Cu3O7-δ Thin Film
Authors: Kimura Hidekazu , Oyanagi Hiroyuki , Terashima Takahito , Yamaguchi Hirotaka , Bando Yoshichika , Mizuki Jun'ichiro
Published: March 2014

The temperature dependence of polarization-dependent EXAFS of a superconducting YBa2Cu3O7-δ thin film has been studied. The measurements were done on the Cu K-edge in the fluorescent mode over the temperature range 30-300K with the a
b plane and the c axis parallel to the X-ray polarization vector, ε. The results indicate that the the values of mean square relative displacement σ(2) of the nearest neighbor Cu-O pairs increase near T

c
in the axial Cu-O bonds.
Theoretical Analysis of Oxygen K-edge in La2-xSrxCuO4 Compounds Based on Multiple-Scattering Theory
Authors: Benfatto M. , Wu Z. Y. , Natoli C. R.
Published: March 2014

In this paper we present a theoretical analysis of the oxygen K-edge in La2-x Srx CuC4 materials based on one-electron multiple scattering theory using a complex optical potential and self-consistent charge density and potential. We obtain good agreement with experimental data both in energy separation and relative intensity between peaks.
XANES Study of Doping and Redox Mechanisms for Hole Creation in Bi(2212) Superconducting System
Authors: Garg K. B. , Saini N. L. , Srivastava P. , Saini B. R. , Merrien N. , Studer F. , Durcok S.
Published: March 2014

A complete set of polarised XAS spectra at Cu L3 and Bi L3- edges have been recorded on a well characterised single crystals of Bi2Sr2CaCu2O8+ superconductor. The Cu L3 spectra shows an energy difference of 400 meV between z(3d3z2-r2
) and x,y(3dx2-y2
) components, with a significant intensity in E ∥ c polarisation. The Bi L3-edges show clearly the energy shift of superconductor spectra towards low energy with respect to Bi(III) references confirming again the Bi-O layers as electron reservoir.
Site of Sulfur Impurities in Silicate Glasses and ReflEXAFS Studies around the Si K-edge
Authors: Lagarde P. , Delaunay R. , Flank A.-M. , Jupille J.
Published: March 2014

The ReflEXAFS technique is used to compare the local order of the silicon-oxygen network close to the surface and in the bulk in doped silica. The structure around the dopant atom (sulfur) is described.
Crystallinity Analysis of Amorphous-Crystalline Mixed Phase Silicon Films Using EXAFS Method
Authors: Wakagi Masatoshi , Kaneko Toshiki , Ogata Kiyoshi , Nakano Asao
Published: March 2014

The crystalline phase fraction (Xc) of amorphous-crystalline mixed phase Si films prepared by thermal annealing of a-Si:H films and by plasma CVD and chemical annealing methods was investigated by an EXAFS method. The EXAFS spectra of these films were represented by linear-combination of a-Si:H and c-Si EXAFS spectra. The values of Xc were analyzed by least-square curve fitting. Furthermore, the Xc values analyzed by a conventional Raman method were calibrated by the EXAFS analysis results.
XAFS Studies of Octahedral Amorphous Oxides
Authors: Burattini E. , Purans J. , Kuzmin A.
Published: March 2014

The relationships between the structures of octahedral and tetrahedral amorphous oxides, studied by XAFS spectroscopy, are considered. It was found that a-WO3, a-MoO3, a-V2O5 thin films and glasses have strongly distorted, but well defined, oxygen octahedra, which are joined by vertices (a-WO3, a-MoO3) or by vertices and edges (a-V2O5), and form a random network. At the same time, a-IrO2 and a-NiO have less distorted oxygen octahedra, which form the rutile type and rock salt type nanocrystalline structures. The variation of the structure with the change of the metal valence is considered and the possibility of small radius polaron detection by XAFS is discussed.
EXAFS Studies of Zinc Halide Glasses–Mixed Halide Systems
Authors: Kadono Kohei , Kageyama Hiroyuki , Kamijo Nagao , Kinugawa Kenichi , Tanaka Hiroshi
Published: March 2014

Structure of mixed halide glasses of ZnCl2-ZnBr2, ZnCl2-ZnI2 and ZnX2-KX' (X, X'=C1, Br, I) systems was investigated by means of Zn K-edge, Br K-edge and I L3-edge EXAFS spectroscopy. The network structure of the ZnCl2-ZnBr2 and ZnCl2-ZnI2 glasses is composed of corner-sharing tetrahedral units, ZnClnX4-n (X=Br, I). The bond distances between zinc and halide ions are similar to those of the corresponding end members though they are slightly varied by the substitution of halide ion. The addition of K+ ions introduces non-bridging halide ions and decreases the bond distance.
Local Structure Changes around Cu Atoms in the Early Stage of Nanocrystalline Formation of Amorphous Fe73.5Cu1Nb3Si13.5B9
Authors: Kim Sang Hyeob , Matsuura Makoto , Sakurai Masaki , Suzuki Kenji
Published: March 2014

Direct evidences that Cu atoms are directly associated with nano-crystalline formation in Fe73.5Cu1Nb3Si13.5B9 (FINEMET) were obtained by fluorescence XAFS measurements. The XAFS results at the Cu K-edge have shown that the local structure around Cu atoms in FINEMET changes from amorphous to fee Cu prior to the bcc-FeSi precipitation.
Structural Studies on Amorphous LaNi5.0 Films as Prepared in Different Methods
Authors: Suenobu Tomoyoshi , Sakaguchi Hiroki , Nishioka Kazuhiro , Kanai Hiroyoshi , Yoshida Satohiro , Adachi Gin-ya
Published: March 2014

Investigation of the local structure around La and Ni atoms in the amorphous LaNi5.0 films prepared by the evaporation and sputtering methods was carried out by means of EXAFS. The short range order in the evaporated film resembled that in the sputtered one and the hydrogen concentration dependence on the change in the local structure in these films well coincided, so that the hydrogen in these films appears to be occupied in the same hydrogen sites.
X-ray Absorption Near Edge Structure (XANES) Studies of Au0.5Ag0.5: Implication for Charge Redistribution at Both Au and Ag Sites upon Alloying
Authors: Bzowski A. , Yiu Y. M. , Sham T. K.
Published: March 2014

L-edge x-ray absorption near edge structure (XANES) has been used to study electronic structure of the titled alloy. It is found that (a) relative to pure Au, the alloy Au L2,3 edge XANES exhibits an increase in absorption coefficient just above the edge, indicating d-charge depletion at the Au site; (b) relative to pure Ag, the intensity of the alloy Ag L2,3 edge “whiteline” of the alloy decreases, indicating d-charge gain at the Ag site; (c) these observations are accompanied by an increase in the Ag L1-edge “whiteline” intensity, a sign for the depletion of p charge. These results are discussed in terms of a charge compensation model.
EXAFS Measurement of Molten Cuprous Halides
Authors: Inui Masanori , Takeda Shin'ichi
Published: March 2014

EXAFS measurement of molten CuCl and CuBr has been carried out near the melting temperatures in order to study the partial structure. EXAFS oscillation was clearly observed and the structural parameters for the nearest neighboring Cu-halogen pairs were obtained from standard curve fit analyses. The obtained Cu-halogen distance is, however, about 0.1A shorter than the distance obtained from neutron diffraction measurement with isotopic substitution. The result may suggest cluster formation such as a CuX trimer (X = Cl, Br) in molten cuprous halides.
Ferroelectric Behaviors in Semiconductive Cd1-xZnxTe Crystals
Authors: Terauchi Hikaru , Yoneda Yasuhiro , Kasatani Hirofumi , Sakaue Kiyoshi , Koshiba Takafumi , Murakami Satoshi , Kuroiwa Yoshihiro , Noda Yukio , Sugai Shunji , Nakashima Shin-ichi , Maeda Hironobu
Published: March 2014

XAFS studies as well as dielectric and X-ray diffraction studies of II-VI semiconductive ternary alloys Cd1-xZnxTe with x=0.0, 0.05, 0.1, 0.2, 0.3, 0.7 and 1.0 were carried out in the temperature range of 10K to 600K. Ferroelectric phase transitions occurred in the mixed crystals with 0.0<x<1.0. Note that in CdTe (x=0.0) and ZnTe (x=1.0) the phase transition does not occur. An anomaly of the structural phase transition was found in the X-ray diffraction studies, however the local structure determined from the XAFS studies was independent of temperature down to 20K.
Evolution of Sn Environment in AlGaAs Alloys
Authors: Pant J. , Pansewicz K. , Zhang J. , Hayes T. M. , Williamson D. L. , Theis T. N. , Kuech T. F. , Gibart P.
Published: March 2014

We have performed fluorescence-detection XAFS measurements on Sn doped AlxGa1-xAs for x = 0.11 and 0.23. The Sn environment is found to change slowly with time.
X-ray Absorption Studies of Ruthenium Silicide
Authors: BZowski A. , Sham T. K. , Yang B. X. , Chen J. M.
Published: March 2014

We have investigated the X-ray absorption fine structures (XAFS) of several ruthenium-silicon intermetallic compounds at the Ru L2,3, Ru K and Si K-edges. From the analysis of the Ru and Si K-edge XANES (X-Ray Absorption Near Edge Structures), particularly the relative intensity of the absorption feature just above the threshold, we found that ruthenium gains p-like electrons upon dilution in silicon. Likewise, compound formation of silicon with ruthenium results in the increase of p-like electrons at the silicon site. The Ru L2,3-edge also exhibits variation in the whiteline intensity for ruthenium silicide of different composition. This is used to infer d charge redistribution at the Ru site upon the formation of Ru-Si intermetallic compounds. The implications of the results are discussed.
EXAFS Study of Cation Distributions in Nickel Zinc Ferrites
Authors: Yao Takeshi
Published: March 2014

Cation distributions in nickel zinc ferrites with various Ni/Zn ratios were analyzed by EXAFS, which can overcome the disadvantage of X-ray diffraction that cannot readily distinguish among different metal ions neighboring on the periodic table. EXAFS of each metal ion was measured, the contribution of the oxide ions for the tetrahedral and the octahedral sites were separated by the least square fitting, then the distribution of the metal ion was obtained. It was found that Ni2+ions mainly occupied the octahedral sites and Zn2+ions the tetrahedral sites. The rest of each sites were occupied by Fe3+ions.
Study of Lanthanum Local Structure in Montmorillonite
Authors: Mun̄oz-Paez Adela , Aaez María Dolores , Alvero Rafael , Castro Miguel Angel , Trillo Jose María
Published: March 2014

SUMMARY: The local structure of the interlamellar lanthanide ions in montmorillonite upon heating is studied. The analysis of the EXAFS data has been carried out using two model environments, that of La3+ aquocomplex and that of the lanthanum oxide. The information thus obtained is crucial in elucidating the intercalation mechanism and demonstrates the important role that XAFS techniques can play in the knowledge of the location and environment of the exchangeable ions in layered silicates.
Lead Titanate is not a Classic Case of a Displacive Ferroelectric Phase Transition
Authors: Ravel Bruce , Stern Edward A. , Yacobi Yitzhak , Dogan Fatih
Published: March 2014

Recent titanium K edge XAFS results show that the ferroelectric to paraelectric phase transition at the Curie temperature (T

c
), 763K, in lead titanate is an order-disorder transition. This contradicts the classic displacive model used to describe this transition. The tetragonal distortion of the perovskite unit cell introduces distinctive structure into the near-edge. This structure shows a weak, monotonically decreasing temperature dependence in the range 10 K to 900 K, and remains in the near-edge even above T

c
where the displacive model would predict its substantial decrease. The Ti EXAFS also indicates that the tetragonal distortion measured by crystallographic techniques below T

c
changes smoothly as the material is heated above T

c
. This continuous variation in the local structure around the titanium atom across T

c
shows that the ferroelectric transition is order-disorder and not the classic displacive model.
L3 Near-edge Structure in Germanium
Authors: Naoe Syun-ichi , Abe Hiroyuki , Fukui Kazutoshi , Matsukawa Tokuo , Murata Takatoshi
Published: March 2014

Ge-L3 spectra in the edge region are devided into two groups according to measurements of absorption for thin films or total electron yield for bulk crystals.
The absorption spectrum with a distinctive peak at the just onset of L
3 edge is concluded to be a near one of a true L
3 spectrum in Germanium. This result is discussed in relation with other experiments and the electronic structure of the germanium crystal.
The L Absorption Edge of Rare Earth Silica Gels
Authors: Stizza S. , Marziali M. , Gzowski O. , Chaboy J. , Marcelli A. , Szaniawska K.
Published: March 2014

To investigate the structural properties of silica-glass formed from the sol-gel technological process, we have investigated by XANES and EXAFS spectroscopy silica-gel doped with several rare earth atoms (Pr, Nd, Eu, Gd) obtained with calcination process at different temperatures (T=750°C, 1000°C and 1250°C). We show that the different gels obtained exhibit significant local order around the rare earth site and expansion of the first shell distance as function of the heat treatment process.
Recent Developments in Multiple-Scattering Calculations of XAFS and XANES
Authors: Rehr J. J.
Published: March 2014

Curved-wave multiple-scattering (MS) theory provides a unified treatment of XAFS, encompassing both EXAFS and XANES, as well as a formal equivalence between exact treatments and the (MS) expansion carried to all orders. Recent developments in the theory of XAFS are reviewed with an emphasis on progress in curved-wave MS calculations and on understanding the nature of MS contributions in EXAFS and XANES. In particular we discuss a unified ab initio MS treatment of XAFS based on a scattering matrix formalism which has sufficient speed and accuracy to treat high-order MS in extended systems. We find that neither low-order MS nor full MS theories are fully satisfactory. Instead, sufficiently high-order MS appears to be necessary for the convergence of both EXAFS and XANES calculations. Our approach also gives a MS interpretation of the σ* shape-resonances observed in XANES. We demonstrate that these peaks result from coherent, high-order MS. We also obtain a generalization of the Natoli rule correlating the resonance locations with bond length.
EXAFS and Ligand Exchange Reaction of Hydrated 3d Transition Metal Complexes
Authors: Miyanaga Takafumi , Sakane Hideto , Watanabe Iwao , Ikeda Shigero
Published: March 2014

Relation between EXAFS parameters and ligand exchange reaction rate constant in solution is investigated. The EXAFS spectra of hydrated 3d metal complexes have been obtained over the temperature range of 20 K to 300 K. The temperature dependences of the mean square relative displacement σ2 and the third order coefficient C
3 in cumulant expansion of EXAFS signal are examined for the first nearest metal-oxygen bond. The ligand exchange rate constant correlates not only with σ2 but also C
3 both obtained from the EXAFS for solid hydrated complexes, and the higher the rate constant, the more rapidly σ2 and C
3 increase with temperature.