S-wave resonances of the negative positronium ion and stability of a system of two electrons and an arbitrary positive charge -: art. no. 052505

We have used a Pekeris-type wave function, expressed on a Sturmian basis in terms of perimetric coordinates, in conjunction with the complex coordinate rotation method, to obtain well-converged estimates of the positions and widths of various S-1(e) and S-3(e) resonances of Ps. Calculations employing bases with one and two length scales were performed. We compare our results to earlier estimates. We also discuss the minimum positive charge that a particle of arbitrary mass must possess in order to bind two electrons.