INTRINSIC PHOTOLUMINESCENCE OF PURE BETA-THBR4 SINGLE-CRYSTAL

The investigation of the intense blue photoluminescence of beta-ThBr4 single crystal has been carried out by optical studies. Absorption and emission spectra versus temperature are presented. The thermal quench ing of the blue photoluminescence has been performed by measuring the temperature dependence of the fluorescence lifetime. The analysis of t hese data yields activation energy value of 3622 cm-1. Using the time- dependent theory, the experimental low temperature emission profile ha s been simulated. The data are interpreted in terms of a charge transf er process between the bromine 4p levels and the thorium 5f-6d levels. A single configuration-coordinate, quadratic coupling model is propos ed to explain the observed decay time thermal dependence.