Title: An effective Hamiltonian approach for Donor-Bridge-Acceptor electronic transitions: Exploring the role of bath memory
Author(s):

E.R. Bittner (Department of Chemistry, University of Houston, Houston TX 77204, USA)

We present here a formally exact model for electronic transitions between an initial (donor) and final (acceptor) states linked by an intermediate (bridge) state. Our model incorporates a common set of vibrational modes that are coupled to the donor, bridge, and acceptor states and serves as a dissipative bath that destroys quantum coherence between the donor and acceptor. Taking the memory time of the bath as a free parameter, we calculate transition rates for a heuristic 3-state/2 mode Hamiltonian system parameterized to represent the energetics and couplings in a typical organic photovoltaic system. Our results indicate that if the memory time of the bath is of the order of 10-100 fs, a two-state kinetic (i.e., incoherent hopping) model will grossly underestimate overall transition rate.

Key words: super-exchange, electron transfer theory, organic photovoltaics, ultrafast dynamics, charge transfer
PACS: 87.15.ht, 82.20.Xr, 82.39.Jn

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