Triplet population and depopulation rates of single terrylene molecules in p-terphenyl crystal

Fluorescence intensity correlation functions of single terrylene molecules in p-terphenyl crystals were measured within the temperature range 5-300 K. The analysis provided the population (k23) and depopulation (k31) intersystem crossing (ISC) rate constants of the lowest excited triplet state T1. These rates increase continuously with temperature, without any noticeable change at the 193 K, temperature of the order-disorder phase transition in p-terphenyl crystal. The depopulation channel composed of the exciting light intensity dependent T1 → Tn absorption followed by the Tn → S1 ISC is important at higher temperatures.