IMPROVED R-SPACE RESOLUTION OF EXAFS SPECTRA USING COMBINED REGULARIZATION METHODS AND NONLINEAR LEAST-SQUARES FITTING

A number of methods have proven to be useful for extended x-ray-absorp tion fine-structure data analysis of disordered systems. Regularizatio n methods, which describe the radial distribution function nonparametr ically, have the advantages of eliminating bias caused by modeling the distribution with a specific functional form, properly including sphe rical wave effects, and allowing the imposition of physical constraint s in a systematic way. In this work we find empirically that the regul arization method reliably resolves subshells that are unresolved by Fo urier transforms and provide unbiased starting models for nonlinear le ast-squares fitting. The method is demonstrated with experimental and simulated data.