Ground-state energy of three-body Coulomb systems through hyperspherical harmonics

The authors use the hyperspherical formalism in order to obtain the ground-state energy for the ions e-e+e-, H- and for the He atom through numerical methods. When studying the convergence trend of the successive approximations they find it behaves comparably with other known applications (although made for short-range forces) and they make use of previous experience to propose an extrapolation formula. The results thus obtained are then compared with those provided by other techniques for the aforementioned systems.