Multiphonon Relaxation of Near-Infrared Excited States of LaCl3:Dy3+

Abstract

Infrared-fluorescence studies and infrared-quantum-counter techniques have been used to investigate multiphonon orbit-lattice relaxation of lower-lying excited states of La${\mathrm{Cl}}_3$:${\mathrm{Dy}}^{3+}$. Multiphonon-relaxation quantum efficiencies and temperature-dependence studies demonstrate that the fast nonradiative decay that is observed is probably due to the emission of several large optical phonons. The spontaneous multiphonon transition rate for the La${\mathrm{Cl}}_3$ host lattice is shown to depend in a systematic and critical way upon the total relaxation energy, i.e., the energy gap between adjacent electronic levels.