Spontaneous Emission Probabilities and Quantum Efficiencies for Excited States of Pr3+ in LaF3

Abstract

Spontaneous emission probabilities for electric‐ and magnetic‐dipole transitions from several electronic states of Pr³⁺ in LaF₃ are calculated using the Judd–Ofelt theory and experimental intensity parameters. The calculated radiative decay probabilities are combined with observed fluorescence lifetimes to determine the quantum efficiencies of the ${}^1{D}_2$ and ${}^3{P}_0$ states. Although the lifetimes were measured at low temperatures and small Pr concentrations where competing nonradiative decay by multiphonon emission and ion‐pair relaxation should be negligible, the predicted quantum efficiencies are less than unity. The radiative lifetimes obtained via the Einstein relations and measured integrated absorption and relative fluorescence intensities agree, however, with the observed lifetimes. The discrepancies appear to arise from approximations and possible limitations inherent in the approach used to calculate the radiative transition probabilities. Matrix elements of $U^{\mathrm{(\lambda )}}$ for states of ${\text{4f}}^2$ in intermediate coupling are included in an appendix.