DELAYED LUMINESCENCE OF ORGANIC MIXED CRYSTALS. VIII. THE LUMINESCENCE OF IMPURE CRYSTALS*,†

Abstract— This paper represents an attempt to understand the delayed luminescence behavior of a real (i.e. impure) mixed crystal. The growth and decay of delayed luminescence is analyzed and shown to be complex. The studies embrace guest and guest concentration dependencies, temperature dependence and excitation intensity and wavelength variation. It is shown that a simple model enables proper interpretation of certain limiting characteristics of the delayed luminescence growth and decay behavior. It is also shown that the temperature dependence of phosphorescence spectra of mixed crystals is readily rationalized and that the complex growth and decay behavior of real crystals are interpretable in terms of guest-guest, guest-trap and trap-trap annihilation phenomena. Differences in the growth and decay lifetimes of a given luminescence are analyzed fully and the reasons for the differences substantiated experimentally. The systems studied consist of aromatics and simple amino acids.