ENERGY DEPENDENCE OF RADIATlVE RATES IN ISOLATED MOLECULES

Much work has been done in the past few years on the problem of the nonradiative decay of single vibronic states in isolated molecules [1,2]. Less attention has been paid to the radiative decay of these levels. Usually rhe nonradiative decay rate is obtained from combined lifetime and quantum yield data. Quantum yields in the gas phase are extremely difficult to determine and large uncertainties are reported. The present note presents a simple relation for the dependence of the radiative decay rate on excess energy, which can be used to check the consistency of observed data and to predict new experimental results. There has been some argument in the literature [2--61 whether vibrational redistribution trikes place prior to emission, or whether the initially prepared state decays before this prows takes place. In the present note we derive formulae, applicable to the decay of single vibronic IeveIs and compare tiem with available experimental data.