Photo- 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 followed by fast migration of the optically released nonrelaxed holes and their 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:Tl and CsI:Pb crystals it has been suggested that the thermally stimulated luminescence peaks observed in CsI crystals at 60 and 90 K arise from closely associated and the separated {V-K-electron centre} pairs, respectively, and that 0 degrees-diffusion of V-K centres can occur when the closely associated pairs are present in the CsI crystals. A scintillation mechanism has been proposed for doped CsI crystals which explains the time and temperature dependences of the scintillations as well as the high efficiency of CsI:Tl and CsI:Na scintillators. (C) 1998 Elsevier Science Ltd. All rights reserved.