EXAFS data analysis

The basic intent behind any EXAFS data analysis is to be able to extract information related to interatomic distances, numbers, and types of backscattering neighbors. In order to accomplish this, there are a number of steps involved in the data analysis, and these include ... 

XRD and LEED are laboratory techniques, although synchrotrons offer advantages for X-ray diffraction. EXAFS, on the other hand, is usually done at synchrotrons. This, and the fact that EXAFS data analysis is complicated and not always without ambiguity, have inhibited the widespread use of the technique in catalysis. 

EXAFS Data Analysis. A key aspect of the analysis outlined above is knowledge of the correct (k) and for a particular absorber-scatterer interaction. These parameters can either be calculated ab initio (6) or can be determined by measuring the EXAFS of structurally characterized model compounds (7). The ab initio method has the advantage that one need not prepare appropriate models for all possible unknowns. Unfortunately however, the ab initio parameters must be adjusted by a scaling factor and an assignment of E, (8). For this reason, one typically calibrates the calculated... 

Data analysis procedures have developed substantially over the last few years. In particular, use of least square refinement methods have been developed. Recent progress with theoretical development for the treatment of multiple scattering has resulted in Ugand group refinement such as an imidazole. We can expect further development in this area which ought to lead us to restrained least square refinement procedures for EXAFS data analysis. This type of restrained refinement is commonly used for macromolecular crystallographic structure determination where a similar problem of imderdeterminancy exists... 

XAFS data collection and EXAFS Data Analysis... 

The first stage in EXAFS data analysis is the removal of the background absorption and the extraction of the EXAFS and its normalization to that for a unit metal atom. An inadequate removal of the background can result in a number of deficiencies in the EXAFS data, which may lead to inaccurate determination of the amplitude function and/or distortions of the low R contribution. The EXAFS may be plotted as a function of k. Often it is convenient to weight the data by... 

EXAFS data analysis consists of varying Eq and the values of—at least—Rj, Nj, and a-j, for each shell of atoms adjacent to the primary absorber, to produce optimum agreement between the experimental and simulated data and their Fourier transforms. 

SR k Boltzmann constant or wave number (latter in context of EXAFS data analysis) COMMONLY USED ABBREVIATIONS Synchrotron radiation... 

Sayers DE, Bunker G (1988) EXAFS data analysis In X-ray absorption Principles, Applications, Techniques of EXAFS, SEXAFS and XANES. Koningsberger DC, Prins R (eds) John-Wiley Sons, New York... 

A brief outline of data analysis procedures is presented below. EXAFS data analysis has been reviewed in great detail elsewhere. " ... 

Two basic methods of EXAFS data analysis have been developed, one based primarily on theoretical principles [9] and the other based on transferable phase and amplitude parameters derived from the study of structurally defined model compounds [1, 13]. Both methods have been successfully applied to the... 

EXAFS data analysis procedures are described in the listed references. Abbreviations L, solvent ligand (methanol in the case listed TMP, meso-tetramesitylporphyrinatof—1) radical NMelm, N-methylimidazole TTP, meso-tetratolylporphyrin THF, tetrahydrofuran TpPP, meso-tetrakis(a,G[,(z,(x-o-pivalamidophenyl)porphyrin ... 

The basic principle of EXAFS data analysis is to reproduce the experimental data with a model based on the expression shown in equation (2-2). In that expression, two kinds of variables are present ... 

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