Emission spectra were measured for separate excitation by light absorbed in the $A$, $B$, $C$, and $D$ impurity absorption bands of single crystals of KI: Tl at 12°K. Five emission bands are reported. Three emission bands are identified as direct transitions from the energy levels related to the $A$, $B$, and $C$ absorption bands. Excitation in the $D$ absorption band is found to excite an additional low-energy emission band which corresponds to a forbidden transition in absorption.

• Received 27 August 1963

DOI:https://doi.org/10.1103/PhysRev.136.A1091