Theoretical studies on core-level spectra of solids

A review is presented of theoretical studies on core-level spectroscopy in solids. In core level spectra, the dynamical response of outer electrons to the core hole is reflected through the screening of core hole potential. Impurity Anderson model (IAM) or cluster model is successfuly applied to the analysis of X-ray photoemission spectra (XPS), X-ray absorption spectra (XAS) and X-ray emission spectra (XES) in f and d electron systems, where the f and d electron states are hybridized with the other valence or conduction electron states. The effect of a core-hole potential plays an important role in these spectra, as well as the hybridization and intra-atomic multiplet coupling effects. Some typical examples for core-level spectra in rare-earth compounds and transition-metal compounds are shown with some discussions.