Rate of Interconversion of Electronic and Vibrational Energy

Radiationless transitions are treated from the viewpoint of the nonstationary character of the Born—Oppenheimer approximation. It is shown that the theory explains the fast rates of internal conversion and highly variable rates of intersystem crossing, accounts for the temperature dependence and selection rules of radiationless transitions, and explains the deuterium effect and external heavy-atom effect on the radiationless transitions.