High-angular-momentum(L>~3)doubly excited resonance states of the positronium negative ion

Abstract

We present a complex-coordinate rotation calculation of the doubly excited high-angular-momentum $(Lg~3)$ resonance states of the positronium negative ion, ${\mathrm{Ps}}^{\ensuremath{-}},$ associated with the $N=3,$ $N=4$, and $N=5$ thresholds of the Ps atom. Products of Slater-type orbitals are used to represent the two-electron wave functions. For the Ps $N=5$ threshold, states with angular momentum up to $L=8$ are calculated. Results for doubly excited intrashell states are used to construct the supermultiplet structures of the energy levels of ${\mathrm{Ps}}^{\ensuremath{-}},$ revealing rotational and vibrational series similar to those for an XYX triatomic molecule.