TIME AND TEMPERATURE-DEPENDENCE OF ANTHRACENE TRIPLET YIELDS IN FROZEN AQUEOUS MICELLAR SOLUTIONS - AN ELECTRON-PARAMAGNETIC-RESONANCE STUDY

Anthracene in frozen aqueous micellar solutions of surfactants n-alkyl trimethyl-ammonium halide (C(n)TAX, n = 10, 12, 14, 16 and 18; X = F, Cl, Br, I) was exposed to laser pulse excitation at 308 nm in the temp erature range 80-270 K. Relative triplet yields and lifetimes were mea sured by electron paramagnetic resonance (EPR) spectroscopy and found to depend on both temperature and environment. A temperature dependent and a temperature independent process is involved in the decay of the triplet state of anthracene. At least three processes compete with in tersystem crossing generating triplets: fluorescence, internal convers ion, and a photoreaction assigned to the formation of anthracene/halid e exciplexes. The last process is strongly dependent on temperature an d indicates significant mobility of reactants below the macroscopic me lting point of the solvent.