Study of defect annealing in γ-irradiated KI by Raman scattering and optical absorption

The annealing behaviour of defects produced in KI by gamma -irradiation at 198K has been studied by optical absorption and Raman scattering techniques. During isochronal annealing, the major optical absorption features, the F band and the double-peaked V band decay at 338K in unison with the 113 cm -1 Raman peak attributed to I 3 - interstitial halogen complexes. This identifies the I 3 - complexes as the major centres complementary to the F centres and responsible for the V band. Isothermal and isochronal annealing studies indicate second-order kinetics for the 338K stage and an activation energy of 1.4 eV. The other substantial Raman feature observed at 173 cm -1 and attributed to I n - (n=5 . . .) halogen complexes is shown to decay at 378K, but is not obviously correlated with any optical absorption feature. It is suggested that these defects are associated with interstitial dislocation loops on their precursors.