Thermoluminescence of strongly irradiated corundum

This paper studies the thermoluminescence of corundum crystals grown by the Kyropoulos method,by directed crystallization, by the Verneil method, and hydrothermally, preirradiated by a flux of 1. 4×10¹⁷ cm_-2 high energy electrons. After this treatment, the individuality of the thermoluminescence curves inherent to each growth method is lost. They become identical and contain five peaks at the temperatures 75, 120-140, 225, 290, and 370°C. After annealing the crystals at 700°C, the thermoluminescence curves return to their original shapes. The single electron peak, presumably from Al⁰_i centre, at 75°C, has a thermal activation energy of 1.0 eV and an optical ionization energy of 2.1 eV.