Electronic Structure of the Vanadate and Tungstate Complexes

The excitation and emission spectra of unactivated yttrium vanadate and calcium tungstate have been measured. Relative absorption spectra were derived from the excitation spectra. In order to aid in the interpretation of the absorption and emission, a series of semiempirical LCAO‐MO calculations were carried out on the vanadate and tungstate complexes. These calculations indicate that the transitions primarily responsible for absorption are the charge transfer transitions t 1 → 2 e and t i → 4 t 2 . The vanadate emission peak is accounted for by an increase of 0.15Aå in the vanadium‐oxygen distance for the excited state. Electrostatic splitting and the effects of lowering of symmetry from T d to D 2 d are discussed.