Time-resolved studies of the nonexponential decay of CsI(Tl) after short-pulse X-ray excitation

The nonexponential decay of CsI(Tl) following excitation by short (20 ns FWHM) X-ray pulses was investigated over a temporal range extending more than six orders of magnitude. The decay appears to be divided into at least three distinct regions, each displaying different kinetic behavior. The behavior can be modified systematically by the inclusion of various foreign modifier ions into the CsI lattice. The temporal dependence of the emission was investigated by means of time-resolved spectroscopy using gated detection, and revealed a significant spectral shift of the emission as a function of time. Some implications of these results with regard to possible reduction of the afterglow will be discussed.