X-ray photoelectron spectroscopic studies of the electronic structure of transition-metal difluorides

The valence-electron densities of states of the $3d$ transition-metal difluorides MnF₂, FeF₂, CoF₂, NiF₂, and ZnF₂ were obtained by means of high-resolution x-ray photoemission spectroscopy (XPS). Except for NiF₂, single-crystal samples were cleaved and studied in ultrahigh vacuum. With the aid of previous XPS results from alkali fluorides, the partial $3d$ densities of states were derived, using the constancy of the F 2s-F 2p energy separation and relative intensity ratio. The results are in very good agreement with recent multiconfigurational Hartree-Fock calculations by Viinikka and Bagus on cluster hole states, both for valence bands and for correlation-state satellite peaks.