Raman and optical absorption studies of proton bombarded CsI

CsI single crystals, which have the simple cubic structure, have been bombarded with 1 MeV protons at a temperature close to 300 K. Optical absorption and Raman studies have identified most of the defects created. These include F and F2 centres, and V centres having absorption bands at 2.7 eV and 3.4 eV, which grow together during irradiation. The Raman studies identify these latter centres as having the I3- structure. Isochronal and isothermal annealing experiments show a mutual decay of the F-type centres and these V centres in a second order reaction with an activation energy of 1.28 eV. The results are discussed in relation to the excitonic mechanism of defect production and the formation of interstitial iodine aggregates of various types in alkali iodides.