Thermoluminescence of alkali halides irradiated at 80 K

Thermoluminescence and optical absorption studies are made on NaCl, NaCl:Cu, KCl, KCl:Cu, KBr and KBr:Cu crystals irradiated by X-rays at 80K. Treated NaCl crystals exhibit a strong first-order glow peak located at 194K with a trap depth of 0.52 eV. Based on F light simulation experiments and by comparison with the known thermal activation energy of F' centres, the filled trap is attributed to the F' centre. Copper doping suppresses the 194K peak and gives rise to two glow peaks centred at 225K and 280K. A strong peak in KBr at 187K with a trap depth of 0.32 eV and a prominent peak in KCl at 219K with a trap depth of 0.40 eV are attributed to the decay of F' centres. Two main glow peaks at first-order kinetics are observed in KCl:Cu crystals at 207K with trap depths of 0.28 eV and 0.53 eV respectively.