Luminescence of complicated thallium centres in CsI:Tl

Emission, excitation and polarization spectra and luminescence decay kinetics have been studied for CsI:Tl single crystals with different thallium concentrations, and the spectral bands of complicated thallium centres separated. The 2.75 eV emission has been ascribed to triplet emission from dimer Tl+Tl+ centres. A similar emission band has been found in polycrystalline CsI:Tl layers and is assumed to be responsible for some important characteristics of the CsI:Tl scintillator. In this paper we give an explanation of these centres and the proposed correlation of the light yield with the thallium dimer centres.