TOWARDS MEMORIES FOR FORSTER-LIKE EXCITON TRANSFER

A simple two-site model (dimer) of the exciton-phonon system leading, in the lowest order in the exciton transfer integral J, to the Forster transfer rates is examined. Dynamics is solved by the Tokuyama-Mori m ethod. The solution in form of damped or overdamped oscillations allow s to deduce standard exciton memory functions in a form summed up part ially to the infinite order in J. Two surprising results are obtained: Up to a decaying initial condition term, an infinite class of memorie s can yield the same exciton dynamics. The simplest choice is even non -decaying unless additional source of dephasing is added. Time integra ls of the memories may not reduce to the standard lowest-order Forster formula if the limitation to just the lowest order in J is performed after the integration. (C) 1998 Elsevier Science B.V. All rights reser ved.