Theory of non-radiative transitions in molecules and solids

Abstract

An extension of a previously proposed theory of non-radiative transitions is presented. It takes account of both strong and weak electron-phonon interaction. A single-frequency oscillator model is used to derive expressions for the transition probability at constant energy on the basis of the adiabatic approximation. The restrictions of both the perturbation theory (weak electronic coupling) and the quasi-classical approximation to nuclear tunneling are removed. Formulae for the transition probability in the high and low energy ranges are derived which are valid for any electronic coupling strength, i.e. for the whole range between the limits of non-adiabatic and adiabatic transitions, for the conditions of both strong and weak electron-phonon interaction.