Final state effects for the core-level XPS spectra of NiO

Abstract

Ionization of the Ni 3s core level in NiO has been studied using ab initio wavefunctions for an NiO6 cluster model. Three important final state effects are studied: (1) ligand to Ni 3d charge transfer, (2) exchange coupling of the ionized core level within the open 3d shell; and (3) atomic correlation effects among the metal 3s, 3p and 3d shells. Analysis of the cluster wavefunctions shows that these mechanisms are strongly coupled and must be treated on an equal footing. The ligand to metal charge transfer is often fractional, i.e. intermediate between 0 and 1. © 1993.