Electron transfer and intramolecular radiationless transitions

We outline the conceptual framework for the description of long-range photoinduced electron transfer in isolated solvent-free supermolecules and explore the dependence of the intramolecular electron transfer rates from photoselected states on the molecular parameters, i.e. energy gaps and mode-specific intramolecular reorganization energies. An energy gap law for the microscopic electron transfer rate was derived which, for relaxation from the electronic origins, exhibits a poissonian energy gap dependence, with an exponential energy gap law for large gaps. The exponential energy gap law manifests the dominant role of nuclear tunnelling in the weak electron-nuclear coupling limit, being quantitatively distinct from the thermal gaussian energy gap dependence.