In situ optical absorption and reflection spectroscopy of doping CsCl crystal with Pb2+ ions

CuCl crystals were doped with Pb2+ ions by thermal treatment of PbCl2-deposited CsCl crystals. At the early stage of the heat treatment, the Pb2+ ions were densely dispersed near the surface of the CsCl crystals, showing impurity-like optical absorption due to 6s to 6p transitions despite the very high concentration (~10 mol %) of the Pb2+ ions. In the case of heavy annealing at a high temperature (673 K) followed by a rapid cooling to room temperature, the Pb2+ ions were uniformly dispersed throughout the CsCl crystals, exhibiting the absorption spectrum due to isolated Pb2+ -ion centers