Fluorescence line narrowing of trivalent praseodymium in lanthanum trifluoride single crystal—Phonon-induced relaxation

Abstract

Phonon-induced relaxation of ${\mathrm{Pr}}^{3+}$: La${\mathrm{F}}_{3}$ is studied by a fluorescence-line-narrowing technique at temperatures from 4 to 50 \ifmmode^\circ\else\textdegree\fi{}K. For temperatures exceeding 15 \ifmmode^\circ\else\textdegree\fi{}K the theory fits the data within the experimental error. For the lowest temperatures, however, mechanisms other than phonon-induced relaxation must contribute to the linewidth. Several such mechanisms are discussed.