Core photoemission theory of semiconducting rare earth compounds

Within the Anderson model and in the case of a filled valence band for which the electron-electron interaction can be treated exactly, we first give a formal description of the corresponding core-photoemission spectrum. Our calculations have been motivated by a number of X photoemission experiments which show up final states problems. We discuss our results in terms of the relative positions of the final 'f' states with respect to the valence band states and in terms of the hybridization between those two types of states. Especially, if the hybridization amplitude is too small (< approximately 1.0 eV) it is not possible to reproduce correctly the experimental (3d) spectrum of CeO2; for somewhat larger hybridization (approximately 1.5 eV) we are able to fit that three peaked spectrum at least in a semiquantitative way. As a consequence, CeO2 can well be considered as an intermediate valent system