  Electron-phonon and electron-electron interactions are in competition in
determining the properties of molecular charge transfer conductors and
superconductors. The direct influence of phonons on the electron-electron
interaction was not before considered and in the present work the coupling of
intramolecular modes to electron-electron interaction (U-vib interaction) is
investigated.The effect of this coupling on the frequency of the normal modes
of a dimer model is obtained and it is shown that frequency shifts of the Raman
active modes are directly related to this coupling. The results are used to
obtain the values of the U-vib coupling constants of intramolecular modes of a
representative molecule of charge transfer conductors, like
tetramethyltetratiafulvalene. Consequences of this coupling on the electron
pairing are also suggested.
