Kramers turnover theory for bridges

The bridge length dependence of the classical transfer rate from donor to a cceptor is studied for symmetric bridged systems. The reaction rate is show n to be factorizable into an escape rate from the donor well and a transmis sion factor through the bridge. As expected for a diffusing particle this t ransmission factor is inversely proportional to the bridge length, for long bridges. The Pollak-Grabert-Hanggi turnover theory is shown to be applicab le for all friction strengths and bridge lengths studied in this paper.