Fluorescence intensity measurements of lead-sensitised Mn2+emission in NaCl and KCl

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Abstract
Energy transfer from lead to manganese ions has been investigated in NaCl and KCl as a function of lead concentration. In both crystals the intensity of the orange manganese emission was found to increase as lead concentration increases up to approximately 45 p.p.m. Beyond this lead concentration, the orange emission decreases probably due to a self-quenching effect taking place in the mixed lead and manganese aggregates. From the fluorescence intensity measurements performed in the crystals, it was concluded that approximately 70% of the lead ions undergo energy transfer in the system NaCl:Pb:Mn and that the efficiency of the Pb to Mn energy transfer process is approximately 75%. In contrast with this result, the number of lead ions undergoing transfer in the system KCl:Pb:Mn was found to be less than 30%. These results are in very good agreement with the ionic radii criteria suggested by Rubio and co-workers (1985). These criteria appear to be quite useful in order to select, for a given alkali halide host crystal, sensitiser and activator impurity ions between which energy transfer is wanted to be produced.