Phosphorescence Lifetime Studies in Some Organic Crystals at Low Temperatures

Abstract

Triplet-singlet decay curves form naphthalene, phenanthrene, chrysene, durene, and hexamethylbenzene have been studied in the crystalline phase at temperatures of 4°K and higher, and for comparison in rigid glass solutions at 77°K. The decay from true dilute solutions was found to follow an exponential law. At 4°K, the phosphorescence emission from crystals of naphthalene, phenanthrene, and chrysene followed an exponential law, while that from durene and hexamethylbenzene was always nonexponential. Various theories concerning the causes of the nonexponential decay and the change in the general shape of the decay curves with different modes of sample preparation and with temperature are discussed.