Microwave-optical double quantum studies of short-lived triplet systems

Abstract

An optical method for the detection of the e.p.r. of phosphorescent systems is described and applied to the study of triplet excitations in crystalline benzophenone at 4.2K. The signals observed can be grouped into two categories which are very different in structure, saturation behaviour, and relaxation time. The signals in one of these categories are shown to arise from triplet excitons. It requires more than one characteristic time to describe the propagation of these excitions; the characteristic times are in the neighbourhood of 1.5 × 10^–11 s and 2 × 10^–10 s. Magneto-optical activity characteristic and magnetic fine structure principal values of the excitons are presented.