Lagrange-mesh calculations of P-wave resonances in three-body atomic systems

Abstract

The resonance energies and widths of the P-wave states of helium and of the positronium ion are studied under the hypothesis that their constituting particles interact trough pure or screened Coulomb forces. The resonances are investigated by combining the Lagrange-mesh method and the complex scaling method. This approach is proved to be efficient: rather simple to implement, fast, and accurate. The obtained results improve by several orders of magnitude the best literature results.