Luminescence of Pr $^{3+}$ Doped LuCl $_3$ and LuBr $_3$ Under Intraconfigurational $(4{\rm f}^2 \rightarrow 4{\rm f}^1 5{\rm d}^1)$ and Band Gap Excitation

The optical properties of Pr 3+ activated LuCl 3 and LuBr 3 under intra-ionic 4f 2 rarr 4f 1 5d 1 and band gap (lambda ex = 193 nm; X-ray) excitations have been evaluated. The luminescence of Pr 3+ in these hosts is found to be strongly dependent on the excitation energy: for energies less than the absorption edge of the host, the luminescence is dominated by the 4f 1 5d 1 rarr 4f 2 interconfigurational optical transitions. When luminescence is excited by photons with energies corresponding to the absorption edge or the band gap of the host, the emission spectrum is dominated by the intraconfigurational 4f 2 rarr 4f 2 optical transitions, which emanate from the Pr 3+ 3 P J states. A model to account for the dependence of the emission behavior of Pr 3+ ion on the excitation energy is presented.