Perturbative treatment of intercenter coupling in the framework of Redfield theory

The quantum dynamics of coupled subsystems connected to a thermal bath is s tudied. In some of the earlier work the effect of intercenter coupling on t he dissipative part was neglected. This is equivalent to a zeroth-order per turbative expansion of the damping term with respect to the intercenter cou pling. It is shown numerically for two coupled harmonic oscillators that th is treatment can lead to artifacts and a completely wrong description, for example, of a charge transfer processes even for very weak intercenter coup ling. Here we perform a first-order treatment and show that these artifacts disappear. In addition, we demonstrate that the thermodynamic equilibrium population is almost reached even for strong intercenter coupling strength. (C) 2001 Elsevier Science B.V. All rights reserved.