Strong electron-phonon interaction in e-e correlated molecular systems

Molecular systems (molecules) with strong electron-phonon interaction are described in terms of the Green functions. In the case of the strong e-ph interaction a general scheme that includes of the Dyson equations for the electron and phonon Green functions, is not productive. Hence, the different methodology is developed where the unitary transformation (that included both electron and phonon subsystems) is used. In this case the Dyson equation for the electron Green function is not valid any longer. Different approximations are proposed. The developed approach is extremely important for electron transfer reactions without single electron transfer assumption. It can be also used in the transport in molecular junction devices.