Showing papers on "XANES published in 1985"
TL;DR: In this paper, a 1% Pt on Cab-O-Sil catalyst was characterized using extended X-ray absorption fine structure (EXAFS) and Xray absorption near-edge structure (XANES).
86 citations
TL;DR: In this paper, angular-resolved XANES spectroscopy of a single crystal of carboxymyoglobin (MbCO) is presented, which can be fully interpreted by multiple-scattering theory which allows the determination of Fe-ligand bond angles.
Abstract: Our knowledge of the structure of condensed matter has been based primarily on spectroscopic methods that measure first-order pair correlations of atomic arrangements and thus provide interatomic distances (for example neutron and X-ray scattering). Bond angles are given by higher-order correlation functions, and such information can be provided by X-ray absorption near-edge structure (XANES) spectroscopy, the features of which are determined by multiple scattering of photoelectrons whose paths begin and end at the selected absorbing atom. We report here angular-resolved XANES spectroscopy of a single crystal of carboxymyoglobin (MbCO). The large dichroism of the X-ray absorption of the crystal can be fully interpreted by multiple-scattering theory which allows the determination of Fe-ligand bond angles. The analysis of the identified multiple scattering features due to CO in high signal-to-noise-ratio spectra of protein in solution has allowed the determination of the variation of CO bond angles. This opens the way to the determination of subtle structural features due to bond angle variations in proteins in solution which are relevant to an understanding of the characteristics of proteins at the atomic scale.
86 citations
TL;DR: In this article, the near edge x-ray absorption fine structure (NEXAFS) spectra of ethylene on Pt(111) at 90 and 300 K have been measured and compared to the spectra calculated using the multiple scattering Xα method for cluster models of adsorbed ethylene and ethylidyne.
Abstract: The near edge x‐ray absorption fine structure (NEXAFS) spectra of ethylene on Pt(111) at 90 and 300 K have been measured and compared to the spectra calculated using the multiple scattering Xα method for cluster models of adsorbed ethylene and ethylidyne. The results indicate that ethylene is adsorbed in the di‐σ configuration (sp3 hybridization) at 90 K, and that the π* orbital retains its identity in this configuration, with no component along the C–C axis. The spectrum obtained at 300 K is attributed to ethylidyne (CCH3) and the calculated spectrum for a cluster consisting of this species bonded symmetrically to three Pt atoms is in good agreement with experiment. The calculations show that the multiple scattering molecular cluster approach is a useful technique for interpreting the NEXAFS spectra of adsorbed molecules.
72 citations
TL;DR: In this paper, a structural approach has been investigated using XANES and EXAFS analysis of the K edge spectra of Cr, Zn and Br. Results of X-ray absorption analysis indicate an octahedral coordination for Cr and Zn, and a delocalisation of X anion.
39 citations
TL;DR: In this paper, the Fe K-edge spectra were measured on FeCl3 aqueous solutions by use of synchrotron radiation to reveal the solute structure from the analysis of Fe Kedge EXAFS and XANES.
Abstract: The Fe K-edge spectra were measured on FeCl3 aqueous solutions by use of synchrotron radiation to reveal the solute structure from the analysis of Fe K-edge EXAFS and XANES. It is concluded that the solute exists mainly as [Fe(H2O)6]3+ but partially as [FeCl(H2O)5]3+ at FeCl3 concentration of 0.1–1 mol dm−3, and it exsits mainly as [FeCl2(H2O)4]+ at the concentration of 3–4 mol dm−3. In the diliquescent product of FeCl3, about a half of the solute is in the state of [FeCl4]− and the remaining half is likely to be in the state of [FeCl2(H2O)4]+. No indication was found for the dimer formation of FeCl3 even in the deliquescent product.
33 citations
TL;DR: In this article, the X-ray Absorption Near-Edge Structure (XANES) was calculated for a series of crystalline oxides of the 3D transition metals from Ca to Cu, and compared with high-resolution experimental data on the cation K-edges.
31 citations
TL;DR: In this paper, the Si 2p image spectra of tetramethylsilane was measured at selected photon energies in the vicinity of the Si2p edge using synchrotron radiation.
Abstract: Photoelectron spectra of tetramethylsilane, were measured at selected photon energies in the vicinity of the Si 2p edge, using synchrotron radiation. In addition to known valence and core Si 2p bands, three LVV Auger lines (69, 76, and 80 eV electron energy) were observed for the first time. Partial and differential cross sections for the Si 2p band and two of the Auger lines have been measured at several photon energies from the Si 2p onset up to 135 eV. An intense resonance is evident in the Si 2p continuum as well as in the LVV Auger decay channels. Its position, right above threshold, accounts for only a part of the absorption feature. Another maximum, already seen in absorption around 124 eV, may be a shape resonance associated with the Si 2p continuum.
29 citations
TL;DR: In this article, high-resolution XANES spectra of insulating lanthanum and cerium 4f 0 and 4f 1 compounds have been measured, and the ground state electronic structure of formally Ce 4+ compounds is given by mixing of multielectron configurations involving oxygen ligand orbitals.
28 citations
TL;DR: In this paper, the F-K X-ray absorption near edge structure (XANES) spectra of alkaline-earth fluorides have been measured with a high energy resolution using synchrotron radiation.
Abstract: F-K X-ray absorption near edge structure (XANES) spectra of alkaline-earth fluorides have been measured with a high energy resolution using synchrotron radiation. Calculations for the observed XANES spectra have been also carried out by use of the short-range order multiple scattering theory. By comparing the observed spectra with the calculated results, we can estimate the effective anion charge distribution of -0.6, -0.65 and -0.795 for MgF 2 , CaF 2 and SrF 2 , respectively. These calculated F K-edge XANES spectra of alkaline-earth fluorides are more sensitive to the charge distribution than cation K-edge XANES.
26 citations
TL;DR: The x-ray absorption near edge structure (XANES) spectra of hemoglobin and myoglobin have been measured at the wiggler beam line of the Frascati Synchrotron Radiation Facility and are interpreted as evidence of some increase of the positive effective charge on the iron atom upon oxygenation.
23 citations
TL;DR: In this article, the authors used X-ray absorption spectroscopy to investigate the near-L-edge structures of Pd in pure Pd and bulk PdSi silicides.
Abstract: X-ray absorption spectroscopy is used to investigate the near-L-edge structures of Pd in pure Pd and bulk ${\mathrm{Pd}}_{2}$Si and PdSi silicides. Possible many-body effects are suggested to explain the apparent discrepancy between the occurrence of ${L}_{2}$,3 white lines and the 4d hole filling in Pd silicides. The interpretations of the extended fine structures and of the near-edge features are correlated with each other in order to find common support for a dynamical relaxation model for the ${L}_{2}$,3 deep core holes of Pd silicides.
TL;DR: Comparative analysis of iron K-absorption-edge shape for hemoglobin derivatives with different ligand affinity suggests strongly that in hemoglobin, iron-forms with high and low affinity are highly improbable.
TL;DR: In this article, it was shown that the linear relationship between concentration and interatomic distance (Vegard's law) which is commonly observed in bulk alloys is not followed in the case of small particles.
IBM1
TL;DR: A brief review is given of the near edge x-ray absorption fine structure (NEXAFS) and surface extended X-ray absorbing fine structure(SEXAFS), which have been developed in conjunction with the availability of high brightness monochromatic synchrotron radiation as mentioned in this paper.
Abstract: A brief review is given of the near edge x-ray absorption fine structure (NEXAFS) and surface extended x-ray absorption fine structure (SEXAFS) techniques which have been developed in conjunction with the availability of high brightness monochromatic synchrotron radiation. Concepts and applications of the techniques are discussed using selected examples of chemisorption problems involving atoms and molecules on surfaces. Extensive references to related work are given.
TL;DR: Iron X-ray absorption near edge structure (XANES) spectra of human fetal and adult deoxyhemoglobin measured at the Frascati synchrotron radiation facility reveal the different geometrical structure of the Fe-porphyrin complexes in the two proteins.
TL;DR: In this paper, the electron system is proved to be the Peierls insulator with a charge density wave of renormalized d electrons of Pt, where the total valence of Pt IV -and Pt 11 is conserved without excess electrons from ligands or anions.
TL;DR: In this paper, the presence of CuO and ZnO in fresh catalysts and of highly dispersed Cu/ZnO after activation and reduction was confirmed by using synchrotron radiation.
TL;DR: In this article, the dopant structure in FeCl3-doped polyacetylene was studied from the analysis of Fe K-edge EXAFS and XANES, measured by use of synchroton radiation.
Abstract: The dopant structure in FeCl3-doped polyacetylene was studied from the analysis of Fe K-edge EXAFS and XANES, measured by use of synchroton radiation. It is concluded that Fe atom is surrounded by four Cl atoms with Fe–Cl distance of 2.19–2.20 A, and the dopant exists in the state of [FeCl4]−. The following mechanism is proposed for the doping process:(CH)x+2yxFeCl3→[CH(Fe(Cl4−)y]x+yxFeCl2It is also shown that the chlorination of polyacetylene occurs significantly on performing a “heavy doping.”
TL;DR: X-ray absorption near edge structure (XANES) spectra of a model compound chelated protoheme methyl ester in solution reveal a linear Fe-C-N configuration as discussed by the authors.
TL;DR: HAL as mentioned in this paper is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not, which may come from teaching and research institutions in France or abroad, or from public or private research centers.
Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. LOCAL STRUCTURE IN SiO2 GLASSES BY OXYGEN K EDGE XANES A. Marcelli, I. Davoli, A. Bianconi, J. Garcia, A. Gargano, C. Natoli, M. Benfatto, P. Chiaradia, M. Fanfoni, E. Fritsch, et al.
TL;DR: In this article, the X-ray-absorption near-edge structure (XANES) spectra for crystalline GaP, InP and GaSb were measured for each Ga and P K-edge region.
Abstract: X-ray-absorption near-edge structure (XANES) spectra for crystalline GaP, InP and GaSb were measured for each Ga and P K-edge region. Full multiple scattering calculations are performed. The information on the charge distribution around the X-ray-absorbing atom can be obtained by comparing the experimental XANES spectra with the full multiple scattering calculations. The effective cation charge distributions are predicted to be q= ~0.33 for GaP, q=0.42 ~0.5 for InP and q \lesssim0.26 for GaSb.
TL;DR: In this article, the Hartree-Foek atomic potentials in ionic crystals were used to construct X-ray absorption near edge structure (XANES) and extended fine structure (EXAFS) of crystals NaCl, KCl, NaF.
Abstract: The scattering wave (SW) method is generalized for the case of Hartree-Foek atomic potentials in ionic crystals. An earlier developed scheme of these crystal potential construction is used to obtain photoelectron scattering phase shifts. X-ray absorption near edge structure (XANES) and extended fine structure (EXAFS) of crystals NaCl, KCl, NaF are then calculated in the single- scattering approximation of the SW-method. The approach used permits to obtain EXAFS of ionic crystals with high accuracy and also the main features of their XANES.
[Russian text ignore.]
TL;DR: In this article, the authors detected the iron site structure modifications induced by the transition from the quaternary R to T structure in ferric carp azide hemoglobin from analysis of multiple scattering resonances in the XANES (X-ray absorption near edge structure) spectra.
TL;DR: In this article, a comparison of XANES spectra of many different core levels, the 4f-5d hybridization and/or the inter-atomic 4fligand orbital mixing gave two different types of mixed valent systems.
TL;DR: In this article, the importance of various types of multiple scattering was systematically assessed, and the dominant multiple scattering paths were identified from both bulk and surface geometries to illustrate the variety of possibilities that may arise.
TL;DR: It is concluded that the electronic environment in the relaxed state is different from that in the as-deposited state and that any accurate structural model of relaxed amorphous germanium must predict the XANES feature at 1221 eV.
Abstract: The ${L}_{\mathrm{III}}$-edge x-ray-absorption near-edge structure (XANES) of germanium is reported as a function of annealing temperature. There are no features in the XANES spectra for as-deposited films, but in an annealed sample (shown by Raman spectroscopy to be in a relaxed amorphous phase) a feature at 1221 eV appears. Upon crystallization of the sample, and additional feature at 1218 eV emerges. We conclude that the electronic environment in the relaxed state is different from that in the as-deposited state and that any accurate structural model of relaxed amorphous germanium must predict the XANES feature at 1221 eV.
TL;DR: The position of line MnKβ1,3 is determined mainly by the valence of manganese spinel oxides with the metal in the formal oxidation states +2, +3, and +4 as discussed by the authors.
01 Jan 1985
TL;DR: In this article, an extension of these studies to other halogen molecules used as dopants of polyacetylene polymethyl methacrylate (CH)x has been presented, showing that both the near-edge structure and the extended fine-structure of the XA spectra yield a variety of information about the doping process and the orientation of the inserted halogen (poly-)anions with respect to the polyethylene chains.
Abstract: Despite of extensive investigations in the last few years, the structural properties of acceptor-doped polyacetylene are still in the midpoint of current debate /l/. This is due to the fact that the doping process leads to drastic changes of the relatively well-known structure of pristine (CH)x accompanied by a loss of long-range coherence and crystallinity. This limits the application of standard X-ray and neutron diffraction techniques. It has recently been demonstrated for the case of (CHBry)x that X-ray absorption (XA) studies can provide detailed information about the chemical form and local structure of the doped species /2,3/. In this contribution, we report on an extension of these studies to other halogen molecules used as dopants of (CH)x. We demonstrate that both the near-edge structure and the extended fine-structure of the XA spectra (called NEXAFS and EXAFS, respectively) yield a variety of information about the doping process and the orientation of the inserted halogen (poly-)anions with respect to the (CH)x chains. Stretch-oriented (CH)x samples, which represent quasi-one dimensional systems, were used in all investigations. This allows us to exploit the linear polarization of the synchrotron radiation (SR) in performing XA studies which are comparable with optical polarizer/analyser experiments.
TL;DR: In this paper, the higher order correlation function of local atomic distribution in amorphous semiconductors has been probed directly by XANES (x ray absorption near edge structure) experiments using synchrotron radiation.
Abstract: The higher order correlation function of local atomic distribution in amorphous semiconductors have been probed directly by XANES (x ray absorption near edge structure) experiments using synchrotron radiation. We show that uniquestructural informations on the geometry of local atomic arrangeaments in amorphousvanadium oxide semiconductors and in silica glasses can be obtained. The multiple scattering theory has been applied to interpret the data.