The ratio of triplet to singlet excited state formation from ion recombination in the radiolysis of aromatic solutes in alkane liquids

Abstract

The rates of formation of solute triplet and excited singlet states as a function of time have been measured over the first 70 ns in the pulse radiolysis of isooctane, cyclohexane, and n-hexane solutions. At 0.1 M solute (naphthalene or biphenyl), the fraction of the solute excited states formed by ion-recombination that are triplet is determined to be 0.5±0.1 in the time regime 2 to 70 ns. A similar value is obtained from analysis of the time profile of the triplet state of naphthalene for concentrations from 0.001 to 0.1 M in the same solvents. The implications of these results with respect to the non-homogeneous ion recombination processes occurring are discussed. The decay rate of the solute radical anion has also been determined, and the relationship between it and the rate of solute excited state formation has been analyzed.