Extreme Correlation Effects in the Elusive Bound Spectrum of C60–

We report on large-scale coupled cluster calculations of the electron affinities of the C 60 fullerene. The full spectrum of bound states of the anion is investigated. Thereby, a new state bound by correlation is discovered. The binding of this state is highly dependent on the correct description of the polarization and the electron correlation in the fullerene. We present the natural orbital occupied by the excess electron for each of the anionic states and show how the bound spectrum can be divided into two different groups according to their binding mechanism. We discuss in depth how approximating the correlation with perturbation theory leads in the case of the C 60 – anion to unreliable predictions of the electron affinities in contrast to other large clusters and molecules. Some possible implications of the new weakly bound state are discussed.