Theory and computation of triply excited resonances: Application to states ofHe−

Autoionizing multiply excited states offer unusual challenges to the theory of electronic structure and spectra because of the presence of strong electron correlations, of their occasional weak binding, of their proximity to more than one threshold, and of their degeneracy with many continua. Here we discuss a theory that addresses these difficulties in conjunction with the computation of their wave functions and intrinsic properties. Emphasis is given on the justification of the possible presence of self-consistently obtained open-channel-like (OCL) correlating configurations in the square-integrable representation of such states and on their effect on the energy E and the width Γ. Application of the theory has allowed the prediction of two hitherto unknown ${\mathrm{He}}^{\mathrm{-}}$ triply excited resonances, the 2s2${\mathit{p}}^2$ ${}_{}{}^2{}_{}{}^{}$P (E=59.71 eV, above the He ground state, Γ=79 meV) and the 2${\mathit{p}}^3$ ${}_{}{}^2{}_{}{}^{}$ ${\mathit{D}}^{\mathit{o}}$ (E=59.46 eV, Γ=282 meV) (1 a.u.=27.2116 eV). These resonances are above the singly excited states of He and are embedded in its doubly excited spectrum. The relatively broad 2${\mathit{p}}^3$ ${}_{}{}^2{}_{}{}^{}$ ${\mathit{D}}^{\mathit{o}}$ state interacts strongly with the He 2s2p ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}^{\mathit{o}}$ εd continuum. The effect of this interaction has been studied in terms of the coupling with fixed core scattering states as well as with a self-consistently computed OCL bound configuration.