Simple model relating recombination rates and non-proportional light yield in scintillators

We present a phenomenological approach to derive an approximate expression for the local light yield along a track as a function of the rate constants of different kinetic orders of radiative and quenching processes for excitons and electron-hole hole pairs excited by an incident gamma-ray in a scintillating crystal. For excitons, the radiative and quenching processes considered are linear and binary, and for electron-hole pairs a ternary (Auger type) quenching process is also taken into account. The local light yield (Y-L) in photons per MeV is plotted as a function of the deposited energy, -dE/dx (keV/cm) at any point x along the track length. This model formulation achieves a certain simplicity by using two coupled rate equations. We discuss the approximations that are involved. fit local light yield profiles needed for qualitative comparison with experiment. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim