Kinetic properties of infrared and visible luminescence induced by electron beam in CsI:Tl crystal

Abstract

Presented are the results of comparative study of the decay kinetics for luminescence in the visible (350 ÷ 700 nm) and infrared (1000 ÷ 1900 nm) spectral regions, which is excited in CsI:Tl crystals by a pulsed electron beam (Еm = 250 keV, t1/2 = 15 ns, j= 8 mJ/cm2). The infrared luminescence is assumed to be caused by radiative transition from the excited 62P3/2 state into the ground 62P1/2 state of Tl0 center. The decay kinetics of this luminescence at temperatures within 77 ÷ 450 К range is found to have two pronounced stages. One of them is exponential with a time constant characteristic for the given temperature and independent of Tl concentration within 0.018 ÷ 0.43 mass% range. The other stage has the same decay kinetics as that of the visible luminescence measured under the same conditions. In terms Tl0-Vk recombination giving rise to Tl-perturbed excitons, the visible luminescence arise due to disintegration of [(Tl0)*,Vk] complexes, where Tl0 center has the populated ψ sub-level of the 62P3/2 excited state. The exponential nature and rather long duration of the visible luminescence decay (τ = 700 ns) at room temperature are determined by the lifetime of Tl0 center in the excited metastable state.