Photostimulation mechanisms of x-ray-irradiated RbBr:Tl

Abstract

The physical mechanism of photostimulated luminescence (PSL) of RbBr:Tl, resulting from x-ray irradiation, has been investigated. Spectroscopic methods have been utilized to identify the bromine F center as the occupied electron trap. By means of absorption studies the charge state of the dopant Tl was found to be monovalent. The spectral emission showed the characteristic Jahn–Teller splitting of the 3P1 state of the Tl+ and its known temperature dependence. PSL lifetime and efficiency experiments have been conducted in the temperature regime from liquid helium to 500 K to understand the charge transport from the F center to the activator and have been compared with corresponding data obtained from direct optical excitation into the A band of the Tl+. The observed temperature dependencies of both lifetimes could be explained by the properties of the s2 ion Tl+. As a resulting model for the PSL process a tunneling from the relaxed excited state of the F center to an excited state of the Tl2+ ion following photostimulation is suggested. The temporal, thermal, and spectral behavior of the subsequent radiative fraction of the deexcitation process is solely determined by the properties of the Tl+ ion in the RbBr matrix.