A XANES study of mixed-valence transition-metal oxides and rare-earth alloys

Energies of the 1s→3d. 1s→4s and 1s→4p transitions of Mn, Fe and Co in a series of oxides have been obtained from X-ray absorption near-edge structure (XANES). Bivalent metal oxides do not show separate features in XANES due to the two oxidation states of the metal, but the spectroscopic transition energies. ET: as well as the 3d-4s and 3d-4p energy differences. δE, increase smoothly with the oxidation number of the metal or its effective atomic charge, q. The variation of transition energies as well as δE values with q is best described by the parabolic relation. ET (or δE)=aq+bq2. Mixed-valence cerium and ytterbium alloys distinctly show transitions due to the valence states in the XANES