OPTICAL-ABSORPTION AND THERMOLUMINESCENCE OF KBR-LIBR CRYSTAL SUBJECTED TO HIGH AC FIELD AND LATER IRRADIATED WITH X-RAYS

A study of the colour centre phenomena in potassium halides and lithiu m halides subjected to high electric fields and subsequently irradiate d with X-rays, gave considerable insight into the electronic processes in these solids.Optical absorptions of KBr-LiBr(5 mole%of LiBr) have been studied in its as-grown condition, subjected to high a.c. (50 Hz) fields up to 40 kV/cm for half an hour and also when these samples ha ve been irradiated with X-rays at room temperature (approximately 32-d egrees-C). The crystal exhibits an absorption coefficient value of 3.1 cm-1 at 330 nm which decreases with wavelength attaining a constant v alue of 2.0 beyond 500 nm. The absorption in the field treated samples increases with the ac field attaining the value of 8.2 at 330 nm for the samples subjected to 40 kV/cm. X-ray irradiated KBr-LiBr shows a p rominent peak at 640 nm and another at 500 nm. The absorption in these bands increases with fields. The thermoluminescence (TL) of this samp le exhibits one peak at 95-degrees-C but the field treated samples sho w two peaks one at 95-degrees-C and the other at 180-degrees-C. The TL light output in these peaks increases with the ac field, the glow pat tern remaining the same and is the maximum for the sample treated at 4 0 kV/cm.