Energy Transfer and Optical Properties ofTl+Centers in NaI(Tl) Crystals

Abstract
Excitation and luminescence emission spectra of NaI(Tl) single crystals with high Tl content (>0.1 mole%) have been analyzed as a function of temperature and concentration. At high Tl concentrations, both single and dual Tl centers influence the optical properties of the crystal. We have found evidence that energy absorbed in the dimer bands is transferred to nearby monomer centers, which then emit it as perturbed or unperturbed monomer emission; the perturbation diminishes and finally vanishes with decreasing temperature.