Lifetime and Motion of Triplet States in Molten Aromatic Systems

First-order (T1) photocurrents in molten naphthalene and anthracene with or without an incorporated aromatic solute are caused by triplet states striking a metal anode. The identification of the active excited state with the triplet state is based on the fact that its lifetime is equal to the triplet lifetime inferred from delayed-fluorescence experiments. The analogy between T1 photocurrents and second-order (T2) photocurrents with respect to field dependence and quantum yield supports this interpretation because Gray et al. have shown that the T2 photocurrent is due to bimolecular triplet interaction in the bulk. Therefore we have used the time dependence of the T1 photocurrent for determination of triplet lifetimes. For various hydrocarbons the values are of the order of 10–100 msec. No temperature dependence is observed.