Raman scattering induced by V-centre aggregates in pure and Ca-doped KI X-irradiated at room temperature

The formation of anion defects created under X and gamma -irradiation at room temperature in pure KI and Ca-doped KI has been studied by optical absorption and Raman scattering techniques. In pure crystals only large iodine clusters with the structure of crystalline iodine are formed, whereas in Ca-doped crystals three stages can be distinguished in the formation of iodine defects as the X-ray dose increases. Experiments show the role played by the divalent cation in the process of stabilisation of the polyiodide centres (I 3 - , I 5 - ), which are the precursors of the formation of larger iodine aggregates.