Effect of quenching on the thermal glow curves from X-ray irradiated KCl and KCl:Pb single crystals

Thermal glow curves of quenched KCl, both pure and doped with PbCl2 have been studied. Quenching from 6500C enhances the glow output by a much larger amount than can be explained on the basis of enhancement of F-centre formation in quenched samples. Further, the glow peaks which are associated with divalent impurities and the first stage of colouration are also intensified by quenching. However, electrolytic colouration (which involves quenching) diminishes the integrated light output, when the coloured crystal is exposed to X-rays and warmed up. Heat-treatment of electrolytically coloured KCl crystals between 110 and 3000C induces a gradual increase of the colloid band at the cost of the existing F-band. In the case of KCl:Pb electrolysis produces F-band along with various forms of Pb (such as Pb0 and Pb-); but subsequent heating does not produce colloid centres in this sample. On the basis of these results it is concluded that, (i) quenching increases emitting centres where electrons and holes recombine during thermoluminescence, (ii) recombination efficiency of electrons and holes may also increase due to quenching. A new peak at 2850C in the thermal glow curve of quenched KCl has been observed. (author)