Untersuchung reversibler Photoprozesse durch Blitzlichtphotolyse II. Triplett‐Triplett‐Annihilation von Anthracen

Using a flash photolysis apparatus, described in a previous paper, the kinetics of triplet decay and delayed fluorescence of anthracene in glycerol solutions in the temperature range of −20°C to + 90°C have been investigated. By statistical analysis of the kinetic curves the triplet decay kinetics in viscous solvents is shown to consist of competing first and second order reactions. The first order contribution originates from a temperature independent first order decay and a pseudo first order quenching process, the latter having an energy of activation less than that of viscous flow. The second order contribution is produced by the triplet‐triplet annihilation process T + T → S * + S , which is diffusion controlled with an energy of activation equal to that of viscous flow, the frequency factor being in good agreement with D EBYE'S formula. The kinetics of delayed fluorescence are discussed in terms of the kinetic equations of P ARKER'S scheme for P ‐type delayed fluorescence. Experimentally the delayed fluorescence is shown to be consistent with the observed kinetics of the triplet decay using P ARKER'S treatment.