A ${}_{}{}^1{}_{}{}^{}$${\mathit{P}}^{\mathit{o}}$ shape resonance in ${\mathrm{Ps}}^{\mathrm{-}}$ lying above the n=2 Ps threshold is calculated using the method of complex-coordinate rotation with Hylleraas-type wave functions. Comparison is made with a calculation using adiabatic potential curves. We also report new results for ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}^{\mathit{o}}$ shape resonances lying above the n=3 and 7 thresholds.

• Received 12 October 1992

DOI:https://doi.org/10.1103/PhysRevA.47.1497