An Attempt to Determine Eosine’s S*→T Transition Probability and Evidence for the Participation of a D–D Redox Mechanism

Using ATU and EDTA as a reducing agent, an attempt was made to determine the transition probability of the singlet excited state to the triplet state. The values obtained are 0.032 for ATU and 0.080 for EDTA. The cause of this difference is not known at present. Deactivation of the triplet state by a leuco dye as well as by the ground state dye was confirmed. In the case of ATU, it was established that a D-D mechanism operates when the concentration of ATU islow and the con centration of dye is high. This conclusion was supported by the fact that at a constant low concentration of ATU the 1/φ—[D]o plot deviates from linearity, when the dye concentration becomes high.