THEORY OF PLASTICO ML IN γ–IRRADIATED ALKALI HALIDE CRYSTALS

The present paper reports the results of some theoretical approach made to the studies of mechanoluminescence (ML) in coloured alkali halide crystals. It is shown that moving dislocations produced during plastic deformation of crystalline materials cause light emission due to several processes like mechanical or electrostatic interaction of dislocations with defect centres, the dielectric breakdown of adsorbed gaseous molecules by the surface accumulated dislocation charges, the generation of holes during decay of mobile dislocations on the surfaces of crystals, etc. On the basis of rate equations, expressions are derived for the rise and decay of ML intensity at a given strain rate. The estimated values of ML intensities for different crystals are found to be comparable with the experimentally observed values. The expression derived are able to explain the dependence of ML intensity on several parameters like strain-rate, defect centre density, temperature, applied stress, crystal- size etc.