Inelastic Losses and Multi-Electron Excitations in X-Ray Spectra

Abstract

An approach is discussed for ab initio calculations of inelastic losses and multi‐electron excitations in core level x‐ray absorption spectra (XAS) The approach is based on first principles calculations of dielectric response using a real‐space Green’s function formalism. Extrinsic losses are calculated in terms of the photoeleetron self‐energy using a many‐pole representation of the dielectric response function and the GW approximation. Multi‐electron excitations correspond to satellites in the spectral function, which is obtained from similar ingredients using a quasi‐boson model. The theory accounts for extrinsic and intrinsic losses as well as interference terms, and yields quantitative estimates of inelastic mean free paths and the many‐body amplitude factor S02. These results improve both the near edge and the extended fine structure.