The Fluorescent Decay of CsI(Tl) Excited by Charged Particles

The fluorescence from a CsI(0.08% Tl) scintillator excited by charged particles which come to a stop within the scintillator has been measured for alpha particles, deuterons, and protons. In the region 0.1 to 0.6 microseconds after its initial rise, the fluorescent decay can be accurately described by a simple exponential. The characteristic time for this exponential decay has been measured at several energies up to 28.7 MeV for a particles and 7.2 MeV for protons. We have found a linear relationship between this decay time and the logarithm of the particle energy, τ = k ln E + τo, where k and τo are constants which are characteristic of the type of stopping particle.