Electronic structures of the bound excited quartet states of the helium anion

The radial and electron-pair density functions of two bound excited states of the helium anion have been calculated at the full configuration-interaction level with an extended basis set. It is shown that the form of the radial density in the (1s2s2p)P-4 and (2p(3))S-4 states of He- is readily interpreted in terms of orbital contributions, even at the full configuration level at which level of theory the notion of an electronic configuration loses its precise meaning. The smaller radial distance of the L-shell maximum in the 4S State relative to the lower-lying P-4 state is interpreted in terms of a higher effective nuclear charge in the 4S state. The more compact electron cloud of the 4S State leads to a narrower intracule density than that observed for the P-4 state. The 4S state is shown to have a Coulomb hole with the same classic form as the ground state of helium but with a radius that is about six times larger. The depth of the Coulomb hole is substantially greater in the 4S state than in the 4P state, as expected from the fact that the correlation energy is greater in the former state. The Coulomb holes of both states exhibit a vanishingly small depth at small interelectronic distances due to the presence of the Fermi hole. [S1050-2947(99)00612-5].