Red luminescence of ZnS: Fe crystals

In order to elucidate the nature of the red emission band at 660 nm in ZnS: Fe crystals, the equilibrium luminescence, the thermoluminescence and the photoinduced EPR signals were measured, using UV, or the simultaneous UV + IR excitations. In addition, the polarization properties and the light-pressure shift of the red luminescence were studied. On the basis of the obtained results and of the data reported in the literature and concerning the red and IR emissions in ZnS: Fe a donor-acceptor model is proposed, in which the transition Cl^2?→Fe³⁺ would give rise to the 660 nm band.