New Approach to Nonradiative Intramolecular Transitions

Abstract

A unified and completely time-independent approach based on Feshbach's formalism for nuclear reactions, in which radiative and nonradiative processes are treated on an equal basis, is used to describe the behavior of isolated molecules in a radiation field. The expressions developed are complete and link excited states of measurable lifetime to resonances arising from the action of Green functions. Approximations in the form of the assumption that the ground and excited states can be described as Born–Oppenheimer states are finally introduced only to show how matrix elements could be estimated and to relate our results to those of previous studies. An important feature of the present formulation is that, except for particular models as the ones used by Jortner and co-workers, it demonstrates that the radiative and nonradiative decay modes for large molecules are independent of each other to a high degree of approximation. Without substantial modification, the present model yields no information about transitions between excited states.