First-principles configurational interaction calculations were made, using cluster models, of the optical transitions of a neutral O vacancy. A transition from the VO ground state, and consequent radiative decay, explained 7.6eV absorption and 4.4eV photoluminescence bands which had been reported. It was suggested that a transition from the metastable structure of VO was responsible for a 5.0eV absorption band. The model accounted for the fact that a 4.4eV fluorescence was stimulated by excitations, in the ultra-violet and vacuum ultra-violet regions, which had differing decay kinetics.

G.Pacchioni, G.Ieranò: Physical Review Letters, 1997, 79[4], 753-6