Non-arrhenius temperature dependence of electron-transfer rates

A surprisingly weak temperature dependence of electron-transfer (ET) rates in a dense medium may be induced by vibrational excitations of high-frequency quantum vibrational modes of the donor and acceptor centers, which accompany ET. Practically activationless ET prevails over a broad range of the free energy gap within the inverted region for moderate values of electron-vibration coupling. The effects of intramolecular vibrational excitations on the primary ET and recombination rates in the photosynthetic reaction center are elucidated.