Time-resolved Ax-luminescence of NaI:Tl under electron pulse irradiation

Abstract

This paper studies spectral-kinetic properties of NaI:Tl cathodoluminescence registered in the region of Ax-band with maximum 425 nm within the time interval of 10⁻⁸-10⁻² s. Ax-luminescence of NaI:Tl crystal has been excited with an electron pulse (Ee = 0.25 MeV, t1/2 = 10 ns, W = 0.003...0.16 J/cm2) at temperatures in the range of 65-300 K. It has been found that the cathodoluminescence kinetics of NaI:Tl crystal at 425 nm has beside the exponential decay (τ = 235 ns at T = 295 K) also three more components: the fastest exponential decay (τ = 12 ns at T = 78 K), post-irradiation rise on a submicrosecond time scale at T≥128 K and slow exponential decay at T≥160 K. A model has been suggested according to which Ax-luminescence at 425 nm is caused by 11→1S0 electron transition of Tl+ ion. It has been explained that the fast decay and post-irradiated rise components are caused by ³P₁→¹P₁ and ³P₀→³P₁ electron transitions of Tl<m^>+ ion, respectively. The scintillation process in NaI:Tl has been discussed.