X-ray attenuation and anomalous scattering factors of medium-<i>Z</i>elements around their<i>K</i>edge

Abstract

An analytic-calculation method enabling the evaluation of the real part of the anomalous scattering factor f\ifmmode\bar\else\textasciimacron\fi{}' from attenuation measurements in the x-ray range is presented. This method utilizes a power law to fit the variation of the experimentally observed mass attenuation coefficients as a function of the photon energy. It uses an analytic expression involving Gauss hypergeometric functions to calculate the dispersion term. A derivation of the relativistic correction to the dispersion term shows it to be smaller than the one used in the scattering-factor tabulation. The calculations using this method are tested for seven elements of medium Z: Pd, Ag, Cd, In, Sn, I and Xe, between 15 and 45 keV. Since they compare favorably with the ab initio calculation, the present approach can be considered as an advantageous alternative to the full calculation.