Impact excitation and Auger quenching of luminescent centres in crystals, with special reference to ZnS:Mn

The impact excitation and Auger quenching rates are calculated for a luminescent centre in a solid. The approximations used are a perturbation approach (equivalent to the Born approximation) and a long-range dipole interaction (equivalent to the Bethe approximation), together with the neglect of exchange. It is shown that the calculation is inapplicable to ZnS:Mn in which the exchange process is enhanced by a matching of energy spacings within manganese with energy spacings within the conduction band. This provides an explanation of the pre-eminence of ZnS:Mn as a material for high-field electroluminescence.