A technique has been developed to study the dissolution kinetics at dislocation sites in sodium chloride single crystals. A parallel beam of light is allowed to fall upon the silvered etched surface of the crystals and the reflected beam is received back on a photographic film. The pattern thus obtained on the photographic film gives information about (i) the structure of the etched surface (ii) the nature of the surface forming the pit and (iii) the slope of the pit at the source of dissolution.

Gamma ray-induced F bands in melt grown mixed crystals of KCl and KBr are studied at room temperature. The effect of dislocations on F-centre density in mixed crystals has been discussed. In addition, the influence of composition of mixed crystals on F band parameters has been studied. The behaviour of observed F bands is correlated to local strained regions and to the configuration of F centre in mixed crystals.