Spectral representation of the three-body Coulomb problem. II. Autoionizing doubly excited states of unnatural parity in helium

Abstract

A spectral approach of configuration interaction type is used to evaluate energies and widths for a wide range of singlet and triplet ${P}^{\mathrm{e}}$ resonance states of helium up to the eighth single ionization threshold. While the present data are in excellent agreement with existing theoretical results (below the $N=3$--$5$ ionization threshold) obtained within an explicitly correlated approach, there are substantial differences with the energies, the widths, and the number of resonances obtained with the stabilization method.