Activated electron transfer at zero reorganization energy induced by a fluctuating donor-acceptor coupling

Area of Science:

• Physical Chemistry
• Chemical Physics
• Materials Science

Background:

• Donor-to-acceptor charge transfer is crucial in many chemical and biological processes.
• Existing models often focus on reorganization energy and polaron formation.
• Dynamic disorder in coupling presents an alternative mechanism for charge transfer.

Purpose of the Study:

• To develop and analyze a rate model for charge transfer driven by fluctuating donor-acceptor coupling.
• To investigate the charge-transfer rate under conditions of low reorganization energy.
• To explore the transition between non-adiabatic and adiabatic transfer regimes.

Main Methods:

• Analytical and numerical modeling of a charge transfer rate model.
• Consideration of both quantum and classical limits for the reaction coordinate.
• Description of an adiabaticity parameter analogous to the Landau-Zener parameter.

Main Results:

• The coupling-fluctuation mechanism can result in significant charge-transfer rates.
• The energy-gap and temperature dependencies of the rate differ from Marcus theory.
• A transition from non-adiabatic to adiabatic transfer is observed.

Conclusions:

• Fluctuating donor-acceptor coupling is a viable mechanism for fast charge transfer.
• Distinct energy-gap and temperature dependencies can serve as experimental signatures.
• This work provides a framework for identifying coupling-fluctuation-induced charge transfer experimentally.