Electronic coherence in mixed-valence systems: Spectral analysis

The electron transfer kinetics of mixed-valence systems is studied via solv ing the eigenstructure of the two-state nonadiabatic diffusion operator for a wide range of electronic coupling constants and energy bias constants. T he calculated spectral structure consists of three branches in the eigendia gram: a real blanch corresponding to exponential or multiexponential decay, and two symmetric branches corresponding to population oscillations betwee n donor and acceptor states. The observed electronic coherence is shown as a result of underdamped Rabi oscillations in an overdamped solvent environm ent. The time evolution of electron population is calculated by applying th e propagator constructed from the eigensolution to the nonequilibrium initi al preparation, and it agrees perfectly with the result of a direct numeric al propagation of the density matrix. The resulting population dynamics con firms that increasing the energy bias destroys electronic coherence.