Isotope effect with nonadiadatic contribution from purely electronic pairing in superconducting fullerides

Summary form only given. The Isotope effect on the superconducting transition temperature is reexamined in the model proposed by Chakravarty et al. where phonons modulate the electron-electron attraction energy on C/sub 60/ molecules. We find additional contributions to the effective interaction that increase the magnitude of the isotope shift. One of these contributions, which is nonadiabaticy has a stronger dependence on the intermolecular motion of electrons, which could result in an eahanced isotope effect in disordered samples.