Core-hole screening and plasmon satellites in calcium

Abstract

The valence bands and the outermost p core levels of Ca metal have been studied by synchrotron radiation photoemission. High-resolution studies of the 3p core levels reveal three peaks and anomalously strong plasmon satellites. It is shown by the Z+1 approximation that empty states in Ca metal which are just above the Fermi level are pulled below $E_F$ by the core-hole potential and the core hole is screened by a 3d electron. Localization of the 3d electron at the core-hole site is confirmed by good agreement between the observed core-level structure and the calculated 3$p^5$3$d^1$ multiplet. This conclusion is consistent with valence-band and core-level photoemission results for the Ca-Si interface and ${\mathrm{CaH}}_2$. Studies of the Ba 5p core levels show structures which are ascribed to the multiplet of 5d-screened 5$p^5$5$d^1$ final states. Possible effects of the poorly screened core-hole states (3$p^5$3$d^0$) on the plasmon satellites are discussed.