Abstract
Absorption, emission and excitation spectra of KI-Tl, KBr-Tl, KCl-Tl and KCl-In crystals have been investigated from 15°K to 300°K. Five absorption band, which are ascribed to the Tl + dimer center, are observed in addition to the Tl + monomer absorption bands in highly doped crystal (>0.01 mole %). Optical properties of the five bands are explained in terms of energy level diagram. The diagram is constructed from (Tl + ) 2 pseudo-molecular model where two Tl + ions are coupled weakly together. It is shown that of the five dimer bands, two are related to the A band, one is to the B band, and two are to the C band.