Recombination and scintillation processes in

This paper reports spectroscopic and scintillation studies of the well established scintillator material . Standard measurements of luminescence emission and excitation spectra have been accompanied by investigations of thermoluminescence and scintillation light yield over a wide temperature range, and by decay measurements under pulsed gamma and VUV excitations at various temperatures. These measurements are interpreted in the framework of a model that includes a recombination centre and a number of electron traps. We demonstrate that some unusual and largely unexplained features of the scintillator, such as a substantial disparity between scintillation and radiative decay times, the presence of slow components in scintillation decays, and a strong temperature variation of scintillation light yield between 150 and 300 K, have their origin in the processes of charge carrier capture and emission by electron traps. Although the nature of these traps remains elusive, most of the trap parameters, such as frequency factors, energy depths, and relative populations, have been estimated. This makes it possible to predict the characteristics of trap-free material and thereby the potential improvements that could be achieved.