Isothermal relaxation of electrical conductivity and luminescence in irradiated NaBr and KBr crystals

It has been established that ionizing radiation increases the electrical conductivity (σ) of alkali-halide crystals (AHC) measured in the 290-5000K range. This phenomenon was explained by the accumulation of cation vacancies which could appear from the decay of electronic excitation into Frenkel cation pairs. However, the radiation-induced increase of σ may also be connected with the accumulation of unbalanced electrons and holes localized at small traps. The study of unbalanced carriers which determine the charge transfer in irradiated AHC is hindered by the fact that direct methods of identifying the carrier type - measurement of the migration rate, high-precision Hall emf measurements - are inapplicable because of the small and changing values of σ. In the present report the authors discuss the results of a study of isothermal relaxation and thermally stimulated luminescence in irradiated NaBr and KBr crystals. In the isothermal regime the kinetic equations have an analytic solution in a number of cases, which makes the interpretation of results easier