Identification of the I− → Pr3+ charge transfer transition in the excitation spectrum of LuI3:Pr3+

The excitation spectrum of LuI3:Pr3+ is dominated by a strong ultraviolet band centered at 320 nm. This band is identified as the I− → Pr3+ charge transfer transition. The Pr3+ 4f2 → 4f15d1 interconfiguration optical transitions are located within the host lattice absorption band. The luminescence of LuI3:Pr3+ under charge transfer excitation is dominated by the Pr3+ 4f2 → 4f2 intraconfiguration optical transitions. The absence of luminescence from the charge transfer state is due fast (nonradiative) relaxation of the charge transfer state into the Pr3+ 4f2 states.