Existence of He2- negative ions with two remote electrons in antibonding orbitals

Calculations of low-lying quartet states of He-2(-) are reported, in which a positively charged core He-2(+) holds two remote electrons in antibonding orbitals, i.e, spending most time either side of and away from the central nodal plane, of similarly large RMS extent. A previously reported 4 Pi(u) state is reinterpreted and shown to be a Rydberg state. Further, a (4)Phi(u) state and a (4)Pi(g), the lowest state of this category, are reported. The calculation, performed in prolate spheroidal coordinates, is variational, utilizing one-electron diatomic-molecule-type orbitals, in full configuration interaction.