Role of Nonlinear Excitation Quenching Processes and Carrier Diffusion on the Nonproportionality of Light Yield in Scintillators

A phenomenological approach is used to derive the light yield in inorganic scintillators as a function of the incident energy, and rates of linear, bimolecular and Auger processes occurring in the electron track initiated by an x-ray or a γ-ray photon. The dependence of the absolute and relative light yields on the rates bimolecular and Auger nonlinear quenching processes is calculated at varying incident energies. It is clearly demonstrated that the nonproportionality is caused by the nonlinear excitation quenching processes occurring within the track under the influence of high excitation density. It can therefore be reduced/eliminated by either eliminating the nonlinear interaction among the excited electrons, holes and excitons or the high density situation can be relieved by diffusion of carriers from the track at a faster rate than the rate of activation of nonlinear processes. An insight of studying these situations and their material parameter dependence will be presented. Inventing new inorganic scintillating materials with high carrier mobility can lead to a class of proportional inorganic scintillators.