Stabilization of radiation defects by impurity ions in ammonium halides

The curve thermoluminescence (Tl) of NH4Cl have peaks at 120 and 190 K after irradiated by X-rays. The first peak is connected with Vk-centers. The second peak is connected with defects NH3+. We established that peak at 190 K is distorted, if ammonium halides are doped by impurity ions. It have 'shoulder' in temperature region 200-240 K. This phenomenon is independent of the kind impurities We observed it in NH4Cl doped by Tl+, Sn2+, Pb2+, Cu+, Eu2+, Nd2+, K+, Cd2+. However, in chloride ammonium doped by Br- ions this phenomenon was not. Therefore, it appear if the crystals are doped by cationic impurities. It is known in pure chloride ammonium Vk-centers and ions NH3+ have absorption band with maximum 380 nm at the temperature of liquid nitrogen. The optical density of this absorption band have two stages decrease with increase of temperature, at 120 and 190 K. Above 200 K absorption is absent. In chlorides ammonium doped by cationic impurities absorption band at 380 nm have three stages decrease with increase of temperature. At 120 and 190 K the optical density was decreased abruptly. Above 200 K it was observed gradual decrease. Therefore, the cationic impurities stabilize the defects NH3+. The level of thermal stabilization this defects depend on interaction of the NH3+ with impurity ions. The locations defects NH3+ and cationic impurities is random. Because of this reason we observe the gradual decrease of the optical density at temperature region 200-240 K