Theoretical Framework for Absorption (Dichroism) and the Resonance-EnhancedScattering of X-rays by Magnetic Materials

摘要

The scattering length common to the attenuation coefficient and cross-sectionsfor the resonance-enhanced scattering of X-rays suffers from a dependence on a spectrum of virtual, intermediate states which contain next to no useful information about the environment of the atoms. It is the dependence of the scattering length on intermediate states that sets the X-ray techniques apart from neutron scattering and other techniques which directly probe properties of magnetic materials, and limits the usefulness physical intuition in the interpretation of empirical X-ray data. As a step toward a legible interpretation, in a language of standard atomic variables, an investigation is reported of a modified scattering length constructed to possess a structure similar to the scattering length for magnetic neutron scattering, namely, it has the mathematical structure of a spherical tensor operator, to which all Racah's methods for electrons in an open valence shell can be applied.