Positron Annihilation in Mn²⁺‐Doped KCl Single Crystals

Abstract

The angular distribution of annihilation photons (ADAP) is measured in pure KCl single crystals and in that doped with Mn2+ impurities to concentrations of 60 and 250 ppm. In unannealed, impurity‐doped crystals, the intensity of the narrow component increases with the increase of the impurity concentration. The narrowing of the ADAP curves is explained by assuming trapping of positrons at impurity induced positive ion vacancies. On annealing, for 60 ppm impurity concentration, the intensity of the narrow component is greater than that for the unannealed sample of the same concentration, indicating dissolution of impurity–vacancy complexes, at elevated temperatures. For 250 ppm impurity concentration, comparing the results of the unannealed and annealed samples no great difference is found between the intensities of the narrow components indicating, that the dissolution of the impurity–vacancy complexes is not appreciable at higher concentrations, on heating.