A criterion is introduced to achieve the assignment of the optical features observed in the excitation spectra of Bi ions incorporated in closed-shell transition metal oxides. The model is based on the calculation of the energy associated with the lowest S → P intra-ionic transition of Bi (A-like transition), the metal-to-metal charge transfer (D-like transition) and the Stokes shift of the corresponding emission.

The luminescence properties of YVO4–Bi3+ are investigated under the action of hydrostatic pressure in the range 0–20 GPa and interpreted on the basis of empirical models and energy level diagrams. In the zircon phase, the pressure induces an energy downshift of the Bi–V charge transfer state and a correlated red shift of the emission maximum. The pressure-induced zircon-to-scheelite phase transition leads to an important shift of the Bi–V charge transfer emission to the deep red. This emission, reported for the first time in the scheelite polymorph, is strongly quenched at room temperature due to radiationless relaxation from the triplet states of vanadate units and from the Bi–V charge transfer state by crossover to lower-lying electronic states.