This paper investigates the influence of activator concentration and temperature on the scintillation process in CsI:Na crystal which was excited by a pulsed electron beam (Eex = 0.25 MeV, t1/2 = 15 ns, W = 0.003...0.16 J/cm2) at temperature within 77-300 K. It has been established that the transition of Na-bound two halide exciton from singlet state causes 3 eV emission of CsI:Na. The capturing of Vk by Na + ion determines the scintillation pulse shape. Thermal liberation of Vk from VkA centers results in an inertial rise of the emission pulse in lightly activated CsI:Na and in a mono-exponential decay of the emission pulse in heavily activated CsI:Na. The value of thermal dissociation energy of VkA centers is 0.24 ± 0.01 eV, which was obtained from the temperature dependences of the emission decay time constant for CsI:2.810-3%Na and of the rise time constant for CsI:2.010-4%Na.
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