Experiments on high excitation density, quenching, and radiative kinetics in CsI:Tl scintillator

Abstract

Information on quenching as a function of electron–hole density through the range of 10 19 to 2×10 20 e–h/cm 3 typically deposited towards the end of an electron track has been acquired using 0.5 ps pulses of 5.9 eV light to excite in the band-to-band or high-exciton region of CsI and CsI:Tl. A streak camera records partially quenched luminescence from self-trapped excitons (STE) and excited activators (Tl +⁎ ). Both the Tl +⁎ and STE luminescence exhibit decreasing light yield versus excitation density N max , but it is only the 302 nm STE luminescence that exhibits decay time quenching dependent on N max . Fitting the STE decay time data to a model of dipole–dipole quenching yields the time-dependent bimolecular rate constant for quenching of STEs (and Tl +⁎ light yield) in CsI at room temperature: k 2 ( t )=2.4×10 −15 cm 3 s −1/2 ( t −1/2 ).