XANES analysis edge structure

EXAFS is part of the field of X-ray absorption spectroscopy (XAS), in which a number of acronyms abound. An X-ray absorption spectrum contains EXAFS data as well as the X-ray absorption near-edge structure, XANES (alternatively called the near-edge X-ray absorption fine structure, NEXAFS). The combination of XANES (NEXAFS) and EXAFS is commonly referred to as X-ray absorption fine structure, or XAFS. In applications of EXAFS to surface science, the acronym SEXAFS, for surface-EXAFS, is used. The principles and analysis of EXAFS and SEXAFS are the same. See the article following this one for a discussion of SEXAFS and NEXAFS. 

In order to gain information on the environments of certain atoms in dissolved species, in melts or in solids (crystalline or noncrystalline), which are not accessible to diffraction studies for one reason or another, X-ray absorption spectrometry (XAS) can be applied, with the analysis of the X-ray absorption near-edge structure (XANES) and/or the extended X-ray absorption fine structure (EXAFS). Surveys of these methods are available 39,40 a representative study of the solvation of some mercury species, ElgX2, in water and dimethylsulfoxide (DMSO) by EXAFS and XANES, combined with quantum-chemical calculations, has been published.41... 

A Sulfur K Edge X-ray Absorption Near Edge Structure (XANES) Spectroscopy method has been developed for the direct determination and quantification of the forms of organically bound sulfur in nonvolatile petroleum and coal samples. XANES spectra were taken of a number of model compounds, mixtures of model compounds, heavy petroleum and coal samples. Analysis of the third derivatives of these spectra allowed approximate quantification of the sulfidic and thiophenic components of the model mixtures and of heavy petroleum and coal samples. These results are compared with those obtained by X-ray Photoelectron Spectroscopy (XPS). 

In 2006, Lobinski et al.1 reported on the imaging and speciation analysis of trace elements to study the element distribution, oxidation state, metal site and metal structure in biological environments using mass spectrometric techniques (LA-ICP-MS, SIMS, MALDI-MS) and non-mass-spectrometric techniques such as micro-PIXE (proton induced X-ray emission), XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) -the latter two techniques are very sensitive due the use of a more intense synchrotron beam.1... 

X-ray absorption near edge structure (XANES) spectrum An analysis from X-ray absorption spectroscopy (XAS) and, in particular, X-ray absorption fine structure (XAFS) spectroscopy. XANES can be used to identify the valence state of arsenic in solid samples (Teixeira and Ciminelli, 2005 Kober et al., 2005). 

In the first section will be presented XAS from the physical principles to data analysis and measurements. Then section 2 will be devoted to a discussion of a few examples to illustrate the power and limitations of XAS for gaining structural information. Examples are focused on EXAFS studies on nanocrystalline materials. Detailed reviews for applications on other fields of materials science or for presenting the complementary information available by the study of the X-ray Absorption Near Edge Structure (XANES) part of the X-ray absorption spectrum can be found in a number of books [3-5], A brief overview of the recent development of the technique regarding the use of X-ray microbeams available on the third generation light sources will be finally presented in the last section. 

In order to better understand the mechanism of antiwear functions it is essential to identify the compounds, as well as the elements, constituting the tribofilm. With the exception of XPS and X-ray diffraction techniques, all other physical techniques to date have focused on elemental analysis. Extended X-ray absorption, fine structure EXAFS and, in particular, X-ray absorption near-edge structure XANES techniques have, been shown to be very sensitive for structural and chemical speciation. The K-edge EXAFS spectroscopy has been used to study antiwear additives and tribofilms of some metals (Koningsberger and Prins, 1988 Martin et al., 1986a Belin et al., 1989). 

In the present work, we report the novel V-based material which can be negative potential material. The reaction mechanism of this V-based material is discussed through crystal and electronic structure analysis using the XRD Rietveld refinement, X-ray absorption near edge structure (XANES) and the... 

Minerals are identified by a variety of techniques. Some minerals can be identified on the basis of their elemental compositions, but diffraction or X-ray absorption near-edge structure (XANES) spectroscopy provides more compelling mineral identification. Diffraction patterns, produced either by electron or X-ray beams, provide a direct measurement of the spacing between planes of atoms in the crystal structure. When coupled with element analysis, diffraction provides mineralogical identification. 

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