Exciton-Induced Luminescence in KI/Tl.

In a single crystal of KI/Tl, emissions from Tl + ion and a certain impurity were observed under excitation of light in the first characteristic absorption band of KI. These exciton-induced luminescences were measured at various temperatures for specimens of several concentrations of Tl + ion. The intensities of the exciton-induced luminescences attained saturated values at about liquid oxygen temperature. In consideration of the amount of energy transferred to the impurity, the saturated intensities of the exciton-induced luminescence from Tl + ion are almost independent of the concentration of Tl + ion in the range of 10 15 ∼10 19 /cm 3 and showed a quantum efficiency as high as 30%. Therefore the migration of an exciton through the crystal was confirmed.