Positronium formation in s-wave positron–hydrogen scattering

Abstract

A two channel version of the Kohn variational method is used with trial functions containing up to 120 linear variational parameters to calculate the R-matrix elements and the positronium formation cross section for the scattering of s-wave positrons by atomic hydrogen. Results are obtained in the energy range between the positronium formation threshold and the lowest excitation threshold of the atom. The positronium formation cross section rises very steeply to a value of [Formula: see text] just above the positronium formation threshold and then rises approximately linearly with positron energy to a value of [Formula: see text] just below the excitation threshold. Owing to the weakness of the coupling between the positron and positronium channels, the elastic scattering cross section for the positron continues smoothly across the positronium formation threshold.