Decay kinetics of high- and low-energy emission in the A band of KCl:Tl

Within a revival of interest in the emission properties of Tl+-like impurity centers in alkali-halide crystals, the problem of a complete interpretation of high-energy and low-energy emissions in the A-band of KCl:Tl remains without a satisfactory explanation. Two previous works reported experimental results relative to spectral and decay-time measurements for low-energy (weak) emission at 475 nm, and for high-energy emission at 300 nm. In the latter case, however, a confirmation of the existence of an anomalous type of behavior in the slow decay time needed to be clarified. The results reported here demonstrate that this anomaly is not present in high-energy emission. On the basis of these more recent experimental results, an attempt is made to obtain a unifying model, one always based on the Jahn-Teller effect, which could serve in interpreting both high- and low-energy emissions.