Atomic multiplet and charge transfer screening effects in 1s and 2p core-level x-ray photoelectron spectra of early 3d transition-metal oxides

We present a comparative analysis of 1 s and 2 p core -level hard x-ray photoelectron spectroscopy (HAXPES) spectra of metallic VO 2 and CrO 2 . Even though the V 1 s and 2 p spectra in VO 2 show similar line shapes except for the absence/presence of a spin -orbit splitting in the core levels, the Cr 1 s and 2 p spectra exhibit distinct main -line shapes. The experimental HAXPES spectra are analyzed by the Anderson impurity model based on the density functional theory + dynamical mean -field theory and a conventional MO 6 cluster model. We examine the interplay between the formation of the intra-atomic multiplet between a core hole and valence electrons and the charge -transfer effect on the chemical bonding followed by the 1 s and 2 p core electron excitations. We demonstrate the advantage of 1 s HAXPES to the routinely employed 2 p one for distinguishing contributions of a metal-ligand and metallic screening from a state near the Fermi level in metallic early 3 d transition -metal oxides.