ON THE ROLE OF RELAXED CHARGE-TRANSFER EXCITATIONS - NI 3S HOLE STATES IN NIO

In this Letter a non-orthogonal configuration interaction study is pre sented for the high-spin coupled final states involved in the Ni 3s X- ray photoelectron spectra of NiO. Charge-transfer effects play an impo rtant role in the interpretation of this spectrum. These effects are i ncorporated in a conceptually attractive way by a non-orthogonal confi guration interaction description, in which the wave functions are expr essed as linear combinations of the reference configuration and relaxe d charge-transfer configurations. The energy separation and relative i ntensities of the high-spin coupled final states were calculated in go od agreement with experiment. Both final states have considerable char ge-transfer character. (C) 1997 Elsevier Science B.V.