Many-body effects in core-level spectroscopy of rare-earth compounds

Abstract Many-body effects in core-level photoemission and core-level photoabsorption are discussed for rare-earth systems, especially for Ce and La compounds, both in metallic and insulating forms. Emphasis is put on effects of metallic mixed valency and insulating covalency of 4f electrons on these spectra. For the insulating compound CeO2, detailed analyses of the 3d core photoemission (3d-XPS) and the 2p core photoabsorption (L3-XAS) are presented by using the impurity Anderson model with a filled valence band. In order to give a consistent interpretation for 3d-XPS and L3-XAS, it is shown to be essential to take account of the Coulomb interactions U fd (between a 4f electron and a photoexcited 5d electron in the L3-XAS) and -U dc (between the 5d electron and a core hole), in addition to -U fc (between the 4f electron and the core hole). Discussions are given on the physical information derived from the analysis, on similarities and differences in spectral features between insulating and metallic systems, and also on some related topics.