Temperature dependence of the lifetime of phosphorescence of some polynuclear hydrocarbons in viscous solution

Abstract

Abstract : In viscous solutions, the rate of decay of the triplet state, as followed by phosphorescence measurements, is a strong function of temperature at normal temperatures and becomes nearly independent of temperature at low temperatures. The experimental data were described best by an equation of the form: k = a+bT exp (-E(1)/RT)+cT exp (-E(2)/RT), where a is the limiting value of the rate constant at low temperatures, and b and E(1), and c and E(2) are the low- and high-temperature pre-exponential factors and activation energies, respectively. The rates of decay of phosphorescence of several aryl hydrocarbons and some halonaphthalenes in viscous solutions were measured at temperatures ranging from 77K to room temperature. In all cases the high-temperature activation energies were less than the corresponding activation energies for the variation of the solvent viscosity with temperature. (Author)