Creation of excitons and defects in a CsI crystal during pulsed electron irradiation

Data presented on the influence of the temperature in the range 80-650 K on the spectral kinetics of the luminescence and transient absorption of unactivated CsI crystals under irradiation by pulsed electron beams (〈E〉 = 0.25 MeV, t_1/2 = 15 ns, j = 20 A/cm²). The structure of the short-wavelength part of the transient absorption spectra at T = 80- 350 K exhibits features, suggesting that the nuclear subsystem of self-trapped excitons (STE's) transforms repeatedly during their lifetime until their radiative annihilation at T≥ 80 K, alternately occupying di- and trihalide ionic configurations. It is established that a temperature-induced increase in the yield of radiation defects, as well as F and H color centers, and quenching of the UV luminescence in CsI occur in the same temperature region (above 350 K) and are characterized by identical thermal activation energies (∼0.22 eV). It is postulated that the STE's in a CsI crystal can have a trihalide ionic core with either an on-center or off-center configuration; the high-temperature luminescence of CsI crystals is associated with the radiative annihilation of an off-center STE with the structure (I^-(I⁰I^- e^-))*.