The luminescence of Pb2+ in alkaline earth sulfates

The luminescence properties of CaSO4:Pb2+ (anhydrite), BaSO4:Pb2+, SrSO4:Pb2+ and PbSO4 (all barite) are reported. Pb2+-doped anhydrite shows Pb2+ luminescence with a remarkably small Stokes shift to the emission. The barites, however, show emission with a much larger Stokes shift. It is argued that the Pb2+ luminescence in these compounds is not due to pure s ↔ p transitions on the Pb2+ ion.