L_2,3 edges of tetrahedrally coordinated d⁰ transition-metal oxyanions XO₄^n-

The L_2,3 edges of compounds containing tetrahedrally coordinated, isoelectronic d⁰ transition-metal oxyanions, TiO ₄^4-, VO₄^3-, CrO₄ ^2- and MnO₄^- have been measured using electron energy-loss spectroscopy (EELS). The general shape of the electron energy-loss near-edge fine structure (ELNES) is found to be remarkably similar for these oxyanions and arises from the atomic multiplet spectrum of the d⁰ transition-metal ion modified by the tetrahedral field due to the oxygen ligands. The observed structure is also discussed within the framework of molecular-orbital (MO) theory. The possibilities of using these spectra as fingerprints for d⁰ transition-metal ions in tetrahedral coordination is discussed. The structure observed at the O K edges is also commented upon in the light of these findings.