Afterglow rise in ruby at constant temperature

The thermoluminescence (TL) emission curve of ruby crystals contains only one emission peak in the region of 600 K after irradiation of crystals at room temperature. Contrary to other corundum crystals there is a low-temperature luminescence that appeared at the very beginning of irradiated ruby crystal heating. The kinetics and lifetime of this luminescence at isothermal decays do not change up to 530 K. From an analysis of the increase in luminescence intensity at each increase in temperature, it was concluded that the activation energy does not change up to 530 K. It is proposed that Cr4+ ions created under irradiation of crystal transform in a big radius state (BRS) as a result of temperature enhancement. This BRS could move through the lattice along chromium ions and in collision with Cr2+ ion recombine by the tunneling process with light emission. The lifetime of the luminescence is 95 min, the activation energy of the transformation is 0.2 eV, and the value of BRS radius is more than 4 nm. (C) 1998 Elsevier Science B.V. All rights reserved.