Low‐Temperature Photoluminescence of the Aggregate Centres in Eu2+‐Doped KCl Crystals

The emission spectra and fluorescence lifetimes of different aggregation products of Eu2+ dipoles in KCl matrix are examined in the range 15 to 300 K. Two aggregation types are formed in dependence on the annealing temperature. The optical properties of the aggregates (i) and (ii) formed at RT and 125 °C are very similar to those characteristic of isolated dipoles. Above 125 °C both aggregates undergo decomposition. A third aggregation product is formed between 200 and 250 °C. Differently from (i) and (ii) the pertinent absorption and emission spectra do not show any vibronic structure. The effect of the above aggregation products on the fluorescence lifetime of isolated dipoles present in crystals is ascertained.