Crystalloluminescence and the nature of the critical nucleus

Abstract

Abstract Crystalloluminescence of NaCl is shown to be an impurity phenomenon, the spectral distribution of, e.g., NaCl with a lead impurity being similar to that of the NaCl (Pb) crystal phosphor. The light is emitted in short pulses of less than 8 × 10−8 sec and it is shown that each pulse is caused by a phase change of a three-dimensional nucleus leading to the growth of an individual crystal. The radius of the critical nucleus of NaCl (Pb) in supersaturated solution, calculated from the number of quanta per pulse, is about 5 × 10−7 cm, which corresponds to a surface energy of approximately 100 erg/cm2. In the presence of Ag, Cu, Tl, Sb, the light pulses and crystals appear in the form of clusters.