Resolution of interatomic distances by fourier analysis of short energy-range X-ray absorption spectra

Based on the example of signals with a known form of functional dependence, as is the case in X-ray absorption spectroscopy (XAS), the applicability of the available general estimates of the frequency resolution limits in the case of determining two close interatomic distances by a Fourier analysis of short energy range XAS spectra is considered. A method for the Fourier analysis of such spectra over a small interval of photoelectron wavenumbers, ∼3–4 Å−1, is proposed. The method is applied to the K-XAS spectra of As calculated for different pressure-induced distortions of the nearest environment of the As atom in an InAs crystal. This made it possible to identify an adequate model for the radial distribution of coordinating In atoms among alternative models and, based on this model, to resolve two As-In distances that differ by 0.03 Å. A Fourier analysis of the experimental As K-XAS spectrum of an InAs crystal subjected to a pressure of 11 GPa performed based on this method made it possible to determine the character of distortions of the nearest environment of the As atom under this pressure; namely, it was found that the radial distribution of the six coordinating In atoms corresponds to the (1 + 4 + 1) model. For this distortion model, the As-In interatomic distances were determined.