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

Information on quenching as a function of electron–hole density through the range of 1019 to 2×1020 e–h/cm3 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 Nmax, but it is only the 302 nm STE luminescence that exhibits decay time quenching dependent on Nmax. 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: k2(t)=2.4×10−15 cm3 s−1/2 (t−1/2).