Studies on Triplet Energy Transfer by Means of an Emission-Absorption Flash Technique. I. Reversible Energy Transfer between Xanthene Dyes and Anthracenes

Choosing eosin and erythrosin as donor and anthracene and 9-methylanthracene as acceptor, we have kinetically investigated the triplet energy transfer process by flash technique involving emission measurement. In these systems the differences of T-levels of donor and acceptor are of the order of kT at most, and it was anticipated that a reversible energy transfer would occur. It has been established that it actually occurs in eosin-anthracene and erythrosin-anthracene, and very likely occurs in erythrosin-9-methylanthracene. Furthermore, it has been found that in the first two systems the energy transfer rate for the process, donor→acceptor is about half that for the process, acceptor→ donor. This means that the rate in the present systems is determined by some other factor than the triplet level. Discussions have been given on the model for energy transfer.