PNNL

Abstract

A strict ab initio many-electron theory was used to calculate the 4f XPS of the free U5? and U4? ions. The calculations, based on relativistic Dirac-Fock self-consistent field (DF-SCF) and Dirac configuration interaction (DCI) WF’s, indicate that the atomic spectra have a considerable multiplet structure. However, the multiplet splitting, which is mainly manifest as a broadening of the 4f (5/2 and 7/2) lines, is not as strong as for the first row transition metals. As expected, the U4? primary peaks are broader and have more associated satellite structure than does U5?. A comparison of a synthetic spectrum for U4? with the observed XPS of UO2 indicates that inter-atomic effects may decrease the multiplet and spin-orbital splitting, relative to the free ion. Notably, the 7 eV satellite characteristic of UO2 is absent from the calculated XPS of U4?.