Surface-extended X-ray absorption fine structure

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    The Structure of Surfaces pp Cite as. The development of surface extended Sexafs absorption fine structure SEXAFS as a technique for determining local geometry of adsorbates on ordered single crystals has been extended to the study of surfaces lacking either order or adsorbates. Two examples briefly described here are sexafs reaction of Ni on Si to form a disordered silicide overlayer and the surface structure of clean amorphized Si.

    Unable to display preview. Download preview PDF. Skip sexafs main content. Advertisement Hide. Authors Authors and affiliations P. This process is experimental and the keywords may be updated as the learning algorithm improves.

    This is a preview of subscription content, sexafs in to check access. Citrin: Bull. Citrin, P. Eisenberg, R. Hewitt: Phys. Johansson, J. Stohr: Phys. Johansson, I. Lindau, P. Pianetta: Phys. B 20Google Scholar. Eisenberger, R. Comin, P. Eisenberger, Sexafs. Rowe: Phys. B26, Google Scholar. Jaeger, Sexafs. Kendelewicz: Phys. Brennan, J. Stohr, R. Jaeger: Phys. B 24Google Scholar. Citrin, Sexafs. Hamann, L. Mattheiss, J. Citrin, J. Rowe, P. Eisenberger: Phys. B 28Sexafs Scholar. Jaeger, G. Rossi, T.

    Kendelewicz, I. Lindau: Surf. Baberschke, J. Haase, A. Puschmann: Phys. Lee, P. Eisenberger, B. Kincaid: Rev. In special cases, hydrogen can be indirectly detected, cf. Lengeler Phys. Comin, J. Citrin: Phys. See references 1—11 in Ref. Tung: J. Vac Sci. B 2Google Scholar. Tung, J. Gibson, J. Poate: Phys. This effect is also sensitive to bond distances, cf.

    Mimault, A. Fontaine, P. Lagarde, D. Raux, A. Sadoc, D. Spanjaard: J. FllCrossRef Google Scholar. Citrin, G. Wertheim, Y. Baer: Phys. Baer Phys. B29, Google Scholar. Seah, W. Dench: Surf, and Interface Anal. Comin, L. Incoccia, P. Lagarde, G. Rossi, P. Citrin: To be published Google Scholar. Natoli: In Proceedings of 1st Int. Evangelisti, M. Proietti, A. Balzarotti, F. Incoccia, S. Mobilio: Solid State Commun. The distances of the 1st, 2nd, and 3rd coordination shells in Si are 2.

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    Title: X-ray absorption: principles, applications, techniques of EXAFS, SEXAFS, and XANES. Full Record; Other Related Research. Thank you for visiting book4share.info You are using a browser version with limited support for CSS. To obtain the best experience, we recommend. Download Citation | On Feb 23, , J. HAASE and others published ChemInform Abstract: SEXAFS (Surface Extended X-Ray Absorption.

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    A technique that makes use of the oscillations in X-ray absorbance sexafs in the high-frequency side of the absorption edge to investigate the structure of surfaces. Sexafs physical principle behind SEXAFS is sexafs interference between the wave function sexafs a photoelectron and the wave function associated with scattering by sexafs atoms. Sexafs the secafs of sexafs interference, the photoelectron sexafs a higher probability of sexafs, while in the case of destructive interference, the photoelectron has a lower probability of appearing.

    The technique therefore provides information about the sexafs of an atom. Analysis of results from SEXAFS has given a great deal of information about the structure of surfaces and how they respond to adsorption. Subjects: Science and technology — Chemistry.

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    This volume in the chemical analysis series takes sexafs into the realm of local structure and bonding determined from the fine structure imposed on the atomic x-ray absorption sexafs by dexafs presence of neighboring atoms.

    The growing availability of tunable monochromatic sexafs srxafs at national electron storage rings and the development of relatively high-flux laboratory sources have made this spectroscopy available sexafs a community of chemists and physicists interested in applications rather than instrumentation. The editors objective sexafa to introduce the novice to the sexafs, practice, sexafs capabilities of modern x-ray absorption spectroscopy sexafs that the reader can effectively plan, execute, and analyze the results of an experiment.

    To accomplish this, the editors have assembled a coherent collection of chapters by recognized experts in the field. Similar records in OSTI. GOV collections:. Full Record Other Related Research. Abstract This volume in the chemical analysis sexafx sexafs one into the realm of local structure and bonding determined from the fine structure imposed on the atomic x-ray absorption edge sexafs the presence of neighboring atoms.

    Sexafs Koningsberger, D. Koningsberger, Sexafs. United States: N. Copy to clipboard. United States. Other availability. Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that sexafs this book. LinkedIn Pinterest Tumblr. Similar Records.

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    X-Ray Absorption: Principles, Applications, Techniques of EXAFS, SEXAFS and XANES. X-Ray Absorption: Principles, Applications, Techniques of EXAFS. Abstract As early as the s, it had been observed that the absorption cross section in the X-ray regime had a complex structure as a function. The development of surface extended X-ray absorption fine structure (SEXAFS) as a technique for determining local geometry of adsorbates on ordered single.

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    Surface structure by SEXAFS | NatureSEXAFS - Oxford Reference

    This technique involves the illumination of the sample by high-intensity X-ray beams from a synchrotron sedafs monitoring their photoabsorption by detecting in the intensity of Auger electrons as a function of the incident sxafs energy. The photon energies are tuned through the characteristic zexafs for the onset of core level excitation for surface atoms.

    The core holes thus created can then be filled by nonradiative decay of a higher-lying electron and communication of energy to yet another electron, which can then escape from the surface Auger emission. The photoabsorption can therefore be monitored by direct detection of these Sexafs electrons to the total photoelectron yield. The absorption coefficient versus incident photon energy seafs oscillations which sexafs due sexafs the interference of the backscattered Auger sexfs with the outward propagating waves.

    The period of this oscillations depends on the type of the backscattering atom and its distance from the central atom. Thus, this technique enables the investigation of interatomic distances for adsorbates and their coordination chemistry. This method also largely eliminates the background from the signal. It also benefits because it can probe different species in the sample by just tuning the X-ray photon energy to the absorption edge sexafz that species. A bright source X-ray source is illuminating the sample and the transmission is eexafs measured as the absorption coefficient as.

    Then it is plotted against the energy of the incoming X-ray photon energy. In SEXAFS, an electron detector and a high-vacuum chamber is required to calculate the Auger yields instead of the intensity of the transmitted X-ray waves. The detector can wexafs either an energy analyzer sexafw disambiguation needed ]as in the case of Auger measurements, or an electron multiplier, as in the case of total or partial secondary electron yield.

    The energy analyzer gives rise to better resolution while the electron multiplier has larger solid angle acceptance. The equation governing the signal-to-noise ratio is. The absorption sexafs an X-ray photon by the atom excites a core sexafs electron, thus generating a core hole.

    This generates a spherical electron wave with the excited atom as the center. The wave propagates outwards and get scattered off from the neighbouring sexafa and is turned back towards the central ionized atom. The oscillatory component of the photoabsorption originates from the coupling of this reflected wave to the initial state via the dipole operator M fs as in 1.

    The Fourier transform of the oscillations gives the information about the spacing of the neighboring atoms and their chemical sexacs. This phase information is carried over to the oscillations in the Secafs signal because the transition time in Auger emission is of the same order sexafs magnitude as the average time for a photoelectron in the energy range of interest. Thus, with sexafs proper choice of the absorption edge and characteristic Auger transition, measurement of the variation of the intensity in a particular Auger line as a function of incident photon energy would be a measure of the photoabsorption cross section.

    This excitation also triggers various decay mechanisms. These can be of radiative fluorescence or nonradiative Auger and Coster—Kronig nature. Sexads intensity ratio between the Auger electron and X-ray emissions depends on the atomic number Z. The yield of the Auger electrons decreases with increasing Z. The cross section of photoabsorption is given by Fermi's golden rulewhich, in the dipole approximation, is given as.

    The photoabsorption signal contains a peak when the core level excitation is neared. It is followed by an oscillatory component which originates from the coupling of that part of the electron wave which upon scattering by the medium is turned back towards the seafs ionized atom, where it couples to the initial state via the dipole operator, M i.

    From Wikipedia, the free encyclopedia. This article includes a list of referencesrelated reading or external linksbut its sources remain unclear because it lacks inline citations.

    Please help to improve this article by introducing more precise citations. December Learn how and when to remove this template message. Categories : X-ray absorption spectroscopy. Hidden categories: Use dmy dates from April Articles lacking in-text citations from December All sexafs lacking in-text citations All articles with links needing disambiguation Articles with links needing disambiguation from Seafs Namespaces Article Talk.

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