Determining the radial pair distribution function from X-ray absorption spectra by use of the Landweber iteration method

The Landweber iteration approach is used to construct the radial pair distribution function (RPDF) from an X-ray absorption (EXAFS) spectrum. The physical motivation for the presented investigation is the possibility to also reconstruct asymmetric RPDFs from the EXAFS spectra. From the methodical point of view the shell fit analysis in the case of complicated spectra would be much more eased if the RPDF for the first shell(s) are computed precisely and independently. The RPDF, as a solution of the fundamental EXAFS integral equation, is examined for theoretical examples, and a detailed noise analysis is performed. As a real example the EXAFS spectrum of curium(III) hydrate is evaluated in a stable way without supplementary conditions by the proposed iteration, i.e. by a recursive application of the EXAFS kernel.