The dynamic properties of the lowest triplet states of pyrazine and pyrimidine in zero magnetic field

Abstract

The technique of microwave induced delayed phosphorescence has been used to determine the dynamic properties of the lowest triplet states of pyrazine and pyrimidine as guests in benzene host crystals at temperatures at and below 4.2 K. We report values for the total lifetimes of the individual triplet sublevels, their relative radiative decay rates, relative populating rates and relative steady state populations. From these experimental data, we can hope to discover the radiationless and radiative pathways responsible for the population and depopulation of the individual triplet sublevels. To this end, we have analysed the data in terms of simple considerations of the various spin-orbit coupling mechanisms involved in these processes. In most cases there is excellent qualitative agreement between theory and experiment.