Thermo- and photostimulated luminescence in LiF : Mg, Ti single crystals irradiated by ions and VUV light

Abstract

A coordinated study of the relaxation of optical absorption induced by vacuum ultraviolet radiation, x-rays, and α -particles, as well as of photo- and thermostimulated luminescence (TSL) of LiF : Mg,Ti crystals (TLD-100) in the 295-750-K interval, has revealed that TSL regions characterized by activation energies E a = 2.2-2.4 eV and anomalously high frequency factors p 0 = 10 21 -10 22 s -1 alternate with regions where E a = 1.5 eV and p 0 = 10 12 -10 14 s -1 . The relative intensities of the TSL peaks produced by UV illumination (10-17 eV) differ strongly under the conditions of selective photon-induced generation of anion excitons, free electrons and holes, or near-impurity electronic excitations. The latter are responsible for the high efficiency of tunneling radi- ative (involving titanium centers) or nonradiative (involving hydroxyl ions) recombination. The analysis of TSL peaks of LiF : Mg,Ti and LiF took into account two-step processes, namely, thermal dissociation of three-fluo- rine molecules and recombination of the products of their decay ( V K and V F centers, H interstices).