Luminescence and lifetimes ofLresonant states in alkali halides

The time behavior of the fast luminescence produced by excitation in the $L$ bands has been studied in KCl crystals, additively $F$ colored. The results obtained show that the luminescence emitted in the temperature range 30-130 °K is characterized by the lifetime typical of the $F$ excited relaxed state. A model has been proposed for the decay from the $L$ states to the $F$ excited relaxed state, from which the luminescence takes place. A second deexcitation process is the tunneling $L$ state-conduction band. This model should be valid for all the alkali halides. From the quantum yields of the luminescence excited with $L$ lights, the fraction of the electrons relaxing to $F$ excited state and the fraction of the electrons freed in the conduction band have been determined. Finally, the order of magnitude of the resonant-state lifetime is determined.