We present a complex-coordinate rotation calculation of doubly excited ${}_{}{}^{1,3}{}_{}{}^{}$${\mathit{D}}^{\mathit{o}}$ resonance states in ${\mathrm{Ps}}^{\mathrm{-}}$ associated with the N=3, N=4, and N=5 Ps thresholds. Elaborate Hylleraas-type wave functions with up to N=1330 terms are used. In addition to Feshbach resonances below various Ps thresholds, we have identified ${}_{}{}^3{}_{}{}^{}$${\mathit{D}}^{\mathit{o}}$ shape resonances with one each lying above the N=3 and N=5 Ps thresholds, respectively, as well as a ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}^{\mathit{o}}$ shape resonance above the N=4 threshold. A physical interpretation of the doubly excited ${\mathrm{Ps}}^{\mathrm{-}}$ is also given.

• Received 28 March 1994

DOI:https://doi.org/10.1103/PhysRevA.50.2155