The NaCl:Cu+ de-excitation mechanism revisited

The fluorescence of the Cu+ impurity centre in NaCl was investigated in the range 19–300 K. Accurate lifetime and quantum yield measurements partially contradict the results obtained in the past by Pedrini. Contrary to what happens in the potassium halides the Cu+ de-excitation mechanism cannot be interpreted simply in terms of the Pedrini model (two excited states in thermal equilibrium are involved in the emission process, one of which is metastable and lies close below the emitting level). The discrepancies are supposed to be related to the instability of the on-centre configuration of Cu+ in NaCl.