EXAFS formula

The EXAFS formula in the approximation of single scattering is the following ... 

The data analysis was performed with use of the classical EXAFS formula (1) within the plane-wave approximation. The amplitude and phase shifts of Teo et al. were used except when otherwise specified in the text. When tabulated and experimental parameters are used on the same data, slight differences appear in the final results (Tables 1 and 3 for CUC2O4 for example). 

Similarly, the total phase-shift function 4>ij k) can be extracted. These functions can then be used to analyze the EXAFS of the compound under investigation. If a standard compound is chosen so that its electronic and chemical properties are close to that of the compound under investigation, then the influence of some usually unknown factors, such as, e.g., Sq or Aj(A), and of some simplifying assumptions made during the derivation of the EXAFS formula, such as, e.g., that of plane waves or that of a Gaussian distance distribution, is minimized. Instead of an absolute value of relative value Ao], describing the difference in devi-... 

During the fit procedure,Ni and as well as o i are varied in an equation corresponding to a single-shell version of the EXAFS formula in Eq. (7). The disorder term then represents the disorder in the compoimd investigated as compared to the disorder in the model compoimd and thus corresponds to Aoj. In addition, the edge energy Eg is varied, which influences directly the calculation of the k scale and which cannot be determined precisely enough a priori. The final fit is shown in Fig. 4l. The results are ... 

The electronic structure of the spinel type compound NiCo204 has been investigated by XANES, EXAFS, and Ni Mdssbauer studies. On the basis of the derived cation valencies, the octahedral and tetrahedral site occupancies as well as the formula in standard notation for spinel compounds could be delineated [25]. 

The first direct characterization of the structure of a sterically hindered diarylgermy-lene in solution was claimed for compound 26 (Ar = Ar5 in formula 11), using EXAFS (extended X-ray absorption fine structure), UVV (7-max 420 nm) and H and 13C NMR114. The UVV spectra of diarylgermylenes (26), their dimerization products (27) and the complexes formed with compounds containingp-electrons (28) were studied in solution115,116. 

It is impossible to explain EXAFS properly without theoretical formulae. In a monoatomic solid, the EXAFS function /ik) is the sum of the scattering contributions of all atoms in neighboring coordination shells ... 

The EXAFS analysis is in good agreement with the proposed formula on MCM(5oo) of (=SiO)i 65Ti(Np)2.35, with a mean number of 1.7 oxygen atoms at 1.81 A... 

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