Concentration dependence of quantum yield of triplet-state production of pyrene in ethanol

Abstract

The quantum yield of triplet-state production of pyrene in ethanol had been measured as a function of concentration. At low concentrations where no dimer fluorescence is detectable the sum of the quantum yields of monomer fluorescence (0.65) and of triplet state production (0.38) is unity within experimental error. At higher concentrations when emission due to an excited dimer occurs, it is shown that as well as fluorescing and dissociating to produce the excited singlet monomer, the excited dimer decays by two further reactions one of which produces triplet monomer. Rate constants are derived for these last two processes and for quenching of the excited singlet and triplet states of pyrene monomer by ethyl iodide.