We have searched for $S$-wave shape resonances in the Ps${}^{-}$ system. The calculations are carried out in the framework of the complex-coordinate rotation method using both Hylleraas-type wave functions involving powers of interparticle coordinates, and the exponential correlated wave functions. We have located an $S$-wave shape resonance lying above the Ps ($N$ $=$ 2) threshold. By changing the mass of the positively charged particle from one unit of the electron mass to infinitely heavy, we have traced this resonance pole from Ps${}^{-}$ to H${}^{-}$. Results for the shape resonance in H${}^{-}$ are comparable with the available results in the literature.

• Received 18 May 2012

DOI:https://doi.org/10.1103/PhysRevA.86.014501