PHOTOSTIMULATED AND THERMALLY STIMULATED LUMINESCENCE AND DEFECTS IN UV-IRRADIATED CSI-TL AND CSI-PB CRYSTALS

It has been shown that the photoionization of impurity centres followe d by fast migration of the optically released nonrelaxed holes and the ir subsequent self-tripping occurs on excitation of CsI:Tl and CsI:Pb crystals in the impurity-induced absorption bands. From comparison of the characteristics of V-K centres optically created at 4.2 K in CsI:T l and CsI:Pb crystals it has been suggested that the thermally stimula ted luminescence peaks observed in CsI crystals at 60 and 90 K arise f rom closely associated and the separated {V-K-electron centre} pairs, respectively, and that 0 degrees-diffusion of V-K centres can occur wh en the closely associated pairs are present in the CsI crystals. A sci ntillation mechanism has been proposed for doped CsI crystals which ex plains the time and temperature dependences of the scintillations as w ell as the high efficiency of CsI:Tl and CsI:Na scintillators. (C) 199 8 Elsevier Science Ltd. All rights reserved.