The coupled-cluster method in high sectors of the Fock space

The coupled-cluster method is applied to high sectors of the Fock space (up to five electrons outside a closed shell). Ionization potentials and excitation energies are calculated for atomic N, O, F, P, and S and their ions. The effect of virtual triple excitations is included, exactly or at several levels of appoximation. These terms are important for accurate results in the high sectors. © 1995 John Wiley & Sons, Inc.