Intramolecular electron transfer in simple model systems: A propagator study

The probability of site-to-site intramolecular electron or hole transfer as a function of time in simple model systems is calculated. Systems studied are the hydrogen molecule, allyl cation, and cyclopropenium ion, in the Hubbard model. We employ the method of electron propagators, using both exact and approximate (molecular orbital and valence bond) ground state wavefunctions. We conclude that the molecular orbital wavefunction affords a good description of the transfer process for a wide variety of systems. The utility of our approach for the calculation of electron transfer rates in which purely electronic effects are dominant is stressed.