Thermally Stimulated Conductivity and Luminescence in KBr Due toγIrradiation at 10°K

Abstract

The annealing behavior of KBr, $\gamma$-irradiated at 10 °K, was studied by means of simultaneous measurements of the thermally stimulated conductivity and luminescence and of the optical absorption. Over the investigated temperature range between 10 and 35 °K, the conductivity and luminescence behaved very similarly, and the latter did not change its spectral distribution. All observed peaks have been ascribed to the annealing of the irradiation-induced imperfections of the lattice structure. Four peaks, appearing at 14, 17, 20, and 24 °K with characteristic activation energies between 0.025 and 0.058 eV, which saturate in intensity after a moderate irradiation dose, are believed to be due to the generation of conduction electrons. A smaller peak at 22 °K, which was observed only in the conductivity data, may be due to ionic motion. The most prominent peak appeared at 27 °K, and it was shown by "thermal cleaning" experiments that this peak is caused by processes with activation energies of 0.062 and 0.100 eV. Here, too, the signals are believed to be caused by conduction electrons and their consecutive recombination with traps. The 0.062-eV process has "mixed-order" kinetics, i.e., there is an excess of recombination centers. At higher irradiation doses, the 0.100-eV process becomes dominant. This process seems to be associated with the first annealing stage of the $H$ band, which had an activation energy of 0.097 eV. A tentative model of the $H$-center decay involves the dissociation of the $H$ center followed by an interstitial-vacancy recombination.