LUMINESCENCE FROM PERTURBED EXCITON STATES

The luminescence of KI(Tl), KBr(Tl), and KCl(Tl) has been investigated at 20°, 80° and 300°K for excitation in the A and D bands. The data indicate that two different centers are necessary to explain the emission. It is suggested that at least one emission band in KI(Tl) and KBr(Tl) results from electronic transitions on the negative ions surrounding the thallous ion. The corresponding emission in KCl(Tl) is not evident. It is also suggested that the emitting center may have the same symmetry as the center responsible for the intrinsic emission in these crystals. © 1968.