FORMATION OF COLOR CENTERS IN CsI CRYSTALS SUBJECTED TO PULSED ELECTRON IRRADIATION.

Time-resolved optical spectroscopy was used in a study of nonactivated CsI crystals excited by pulses of accelerated electrons (E equals 0. 25 Mev, j equals 10**2 A/cm** minus **2, t//p equals 10** minus **8 sec). The optical absorption spectra were recorded at the ends of the electron pulses at temperatures T equals 80-650 K. These spectra indicated the presence of Frenkel defects, and F, H, and alpha color centers. The efficiency of formation of the color centers was very low for an alkali halide crystal and the rate of spontaneous recombination of these centers after the end of the radiation pulse was high. The results obtained were interpreted by the exciton mechanism of formation of the Frenkel pairs. The activation energy needed for the separation of the components of the H-F pairs in the bulk of CsI was found to be 0. 2 plus or minus 0. 03 ev. Direct evidence was obtained to show that the capture of electron excitations by intrinsic radiation defects formed earlier played an important role in the accumulation of stable color centers.