Thermal recovery and thermoluminescence of room temperature x-irradiated NaCl:Pb2+ single crystals

The thermoluminescence (TL) spectrum of NaCl:Pb2+ single crystals x-irradiated at room temperature consists of seven glow peaks that obey second-order kinetics. The bands in the wavelength spectrum of the emitted light correspond to different emissions of Pb2+ ions. A parallel study of the thermal stability of defects produced by the irradiation shows that the Pb+ ions and F-centres annihilate during TL; at the same time Pb2+ ions are recovered. A model is proposed in which holes and interstitials are trapped together by different defects. When they are thermally activated the hole recombines with a Pb+ yielding a Pb2+ ion in an excited state which gives the observed emission; simultaneously the interstitial recombines with an F-centre and regenerates the perfect lattice. (author)