Influence of phonons on exciton transfer dynamics: comparison of the Redfield, Forster, and modified Redfield equations

The effect of the reorganization of phonons on exciton transfer dynamics is examined. Starting from a general quantum master equation, we obtain population transfer rates for the Redfield, the Forster, and the modified Redfield equations and compare the predictions of these three models over various ranges of parameters. It is shown that the validity of the traditional Redfield equation is justified by a broad spectrum of phonons rather than a small magnitude of electron-phonon coupling strength as is usually implied. The modified Redfield equation suggested by Zhang et al. [J. Chem. Phys. 108 (1998) 7763] is shown to have a wide range of applicability and to reduce numerically to the traditional Redfield equation and the Forster equation in the respective limiting cases. (C) 2002 Elsevier Science B.V. All rights reserved.