Optical absorption intensities and fluorescence dynamics of ions in

Abstract

Optical absorption and fluorescence spectra have been systematically investigated in -doped crystals. The energy position and symmetry character of the Stark levels in the near-infrared region are deduced. The room-temperature absorption line strengths have been experimentally determined and the theory of Judd and Ofelt is used to obtain the radiative lifetimes and branching ratios of the emitting and states. Non-radiative relaxation processes are found to contribute to the transition probabilities of both states. In the case of the multiplets, a multiphonon relaxation process with an effective phonon energy of accounts for the temperature dependence of the lifetime. The -state luminescence shows a non-exponential decay time which indicates the existence of an energy transfer process. This energy transfer process exhibits a Boltzmann-type temperature dependence and is attributed to two-phonon-assisted energy transfer.