Time-Resolved Fluorescence Line-Narrowing Studies in LaF3:Pr3+

We report the direct observation of energy migration and spectral diffusion in the ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$ state of La${\mathrm{F}}_3$: ${\mathrm{Pr}}^{3+}$ using the technique of time-resolved fluorescence line narrowing on the resonant ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}\to {}_{}{}^3{}_{}{}^{}H_4^{}{}_{}{}^{}$ transition. The temperature dependence of the migration process has been measured and various possible transfer mechanisms are discussed. In addition a variation in the excited-state lifetime as a function of absorption frequency and a concentration broadening at zero delay in the nonresonant transition ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}\to {\left({}_{}{}^3{}_{}{}^{}H_6^{}{}_{}{}^{}\right)}_1$ (the lowest Stark level) are reported.