Electron-energy-loss near-edge structures in the oxygenK-edge spectra of transition-metal oxides

Oxygen K-edge electron-energy-loss spectra have been recorded for several transition-metal oxides (NiO, MnO, ${\mathrm{MnO}}_2$, ${\mathrm{TiO}}_2$, ${\mathrm{Cr}}_2$ ${\mathrm{O}}_3$, ${\mathrm{Mn}}_2$ ${\mathrm{O}}_3$) of different crystal structures. The origin of the distinct features which can be identified over 40 eV above threshold is discussed in terms of resonance scattering within shells of neighboring anionic backscatterers. Full multiple-scattering calculations corroborate and correct the simple approach. The first peak at threshold is due to transitions to oxygen 2p states hybridized with the narrow metal 3d band which is highly localized around the metal-atom sites. The other near-edge structures are dominated by the arrangement of oxygen anions around the excited central atom.