Oxygen 1<i>s</i>x-ray-absorption edges of transition-metal oxides

TLDR

The oxygen 1s X‑ray absorption edges of 3d transition‑metal oxides show covalent mixing of metal and oxygen states, producing oxygen p character in unoccupied states and yielding spectra with a sharp double‑peaked near‑threshold region linked to metal 3d states and a broader 5–10 eV region associated with metal 4s/4p bands. The data are analyzed in terms of ligand‑field and exchange splittings. The oxygen p character extends up to 15 eV above threshold, and the splitting between the two sharp peaks near threshold closely matches the ligand‑field splitting, though the relative peak intensities remain unexplained.

Abstract

The oxygen 1s x-ray-absorption edges of a series of 3d-transition-metal oxides have been measured. The structures at the edge arise from covalent mixing of the metal and oxygen states, which introduces oxygen p character in unoccupied states of mainly metal character. The spectra can be divided into two regions: The first is a double-peaked sharp structure near threshold, which can be related to the metal 3d states; the second is a broader structure 5--10 eV above the edge and is related to the metal 4s and 4p bands. We attribute the oxygen p character up to 15 eV above threshold to mainly oxygen 2p character. The data are analyzed in terms of ligand-field and exchange splittings. It is shown that the splitting between the two sharp peaks near threshold is related closely to the ligand-field splitting, but the relative intensities of the peaks are not fully explained at the present time.