``Temperature Effect'' on Triplet State Lifetimes in Solid Solutions

The phosphorescence lifetimes of several aromatic hydrocarbons and their deuterated counterparts have been measured in plastic matrices as a function of temperature. The onset of a dark process at higher temperatures is generally observed and is believed to be a property associated with the aromatic molecule, rather than with some ``unknown'' quencher. Phonon involvement is suggested by the data. An apparatus for accurately measuring phosphorescence decay over seven half-lives with minimal noise is also described.