Thermo-and photostimulated luminescence of CaI2: Tl and CaI2: Pb crystals

Abstract

Thermo-and photostimulated luminescence of CaI2: Tl and CaI2: Pb scintillation crystals under optical and X-ray excitation is studied. It is shown on the basis of the results obtained with account for the data of studies of photo-and X-ray-luminescent properties of these scintillators that Tl+ and Pb2+ ions form complex capture centers with host defects. These centers are responsible for the thermostimulated luminescence in the temperature range of 150–295 K, and the centers of charge carrier trapping are spatially separated from the centers of recombination emission. An assumption is made that thermo-and photostimulated luminescence of CaI2: Tl and CaI2: Pb crystals under optical excitation is observed mainly due to the delocalization of charge carriers from hydrogen-containing centers responsible for the excitation band at 236 nm and the photoluminescence of CaI2 with a maximum at 395 nm. The luminescence of CaI2: Tl crystals in the 510-nm band and CaI2: Pb crystals in the 530-nm band is determined by the radiative decay of near-activator excitons.