Laser‐Induced Coloration and Discoloration Processes in Alkali Halides

The coloration kinetics of KCI, KBr, KI, and NaCl crystals under XeCl excimer laser irradiation ( hv = 4.02 eV) at room temperature as well as laser‐induced discoloration of preliminarily X‐ray coloured crystals, including samples with M and R centres are studied. It can be concluded from the results that the achieved colour centre concentrations are determined by a dynamical equilibrium between laser two‐quantum coloration and a concomitant one‐quantum bleaching of the created centres. Most probably the bleaching proceeds via the laser‐light‐induced destruction 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‐created ones.