SWITCH PHENOMENA IN MOLECULAR 3-CENTER ELECTRON-TRANSFER SYSTEMS WITHSTRONG ELECTRONIC-VIBRATIONAL COUPLING

Three-centre molecular and supramolecular electron transfer (ET) is im portant in device-like function of organized assemblies of bridge-grou p separated donor and acceptor units in solid-state or electrochemical systems. Other areas are solid-state phonon-kick charge capture, elec trochemical ET via adsorbates or film impurities, large adsorbate STM, and long-range ET in redox metalloproteins. Optical three-level analo gues are molecular Raman scattering and two-photon absorption. Three-l evel ET behaviour rests on coupling to environmental nuclear motion. A frame is second order perturbation theory including full vibrational manifolds in all three states. We discuss such a formalism. Common sup erexchange is recovered for high intermediate state energies while vib rationally unrelaxed state population emerges for low energies. These limits are separated by finite resonances in characteristic ''switch'' patterns. Intermediate state vibrational friction is briefly addresse d and we note some biological and synthetic systems to which the forma lism is appropriate.