Approximations in the theory of charge transfer through bridged systems

Using Laplace transforms, analytical approximations are obtained in a simpl e way for the probabilities of charge transfer between donor and acceptor s tates coupled by a bridge. As a test, these are compared with accurate and numerical calculations when the bridge is treated as a standard diatomic Hu ckel chain, whose energies lie in two separate bands, the lower (upper) ban d being completely full (empty). The analytical approximations are found to be generally accurate and provide useful insight into the charge transfer process. (C) 1999 John Wiley & Sons, Inc.