V centres produced in KBr and KCl at 290 K by electron irradiation

Optical absorption techniques have been used to study the effects of plastic deformation at 80 and 290 K on V centres in KBr and KCl produced by 2 MeV electron irradiation at 290 K. It is suggested that new V centres present in deformed crystals are associated with halogen interstitials trapped at dislocations (V x band) and at impurities dispersed during dislocation motion (V s band). The V 3 band in KBr and the 6.4 eV band in KCl present in undeformed material decrease during deformation of irradiated crystals. The V x band appears in two stages on warming after deformation at 80 K. It is proposed that moving dislocations ionize or dissect interstitial defects in their path. The reaction products become mobile at higher temperatures and can diffuse to dislocations to produce V x absorption.