LASER-INDUCED COLORATION AND DISCOLORATION PROCESSES IN ALKALI-HALIDES

The coloration kinetics of KCl, KBr, Ki, and NaCl crystals under XeCl excimer laser irradiation (hv = 4.02 eV) at room temperature as well a s laser-induced discoloration of preliminarily X-ray-coloured crystals , including samples with M and R centres are studied. It can be conclu ded from the results that the achieved colour centre concentrations ar e determined by a dynamical equilibrium between laser two-quantum colo ration and a concomitant one-quantum bleaching of the created centres. Most probably the bleaching proceeds via the laser-light-induced dest ruction of the F centre complementaries, V centres and annihilation of some produced mobile products (H interstitials?) with F centres. The X-ray-created F centres seem to bleach more rapidly than the laser-cre ated ones.