Scaling behaviour of positronium formation cross sections for positron scattering from hydrogen-like ions

Abstract

Positronium (Ps) formation processes of hydrogen (H)-like ions by positron impact are investigated by employing the two-centre two-channel eikonal final state-continuum initial distorted wave model. The differential and integrated cross sections for Ps formation into the ground state are calculated for ions A(Z − 1) + with nuclear charge Z = 1–9. Comparisons with the first-order Coulomb–Born and the continuum distorted-wave final-state models are made. The differential cross sections and the Thomas double-scattering processes for H-like ions are investigated. For the integrated Ps formation cross sections, a scaling law is introduced and it is reasonably followed by H-like ions with Z ⩾ 3 in the entire energy range. The maximum positions of the ground Ps formation cross sections for the H-like isoelectronic sequences are found to be in good agreement with the wave vector matching model of Charlton (2006 J. Phys. B: At. Mol. Opt. Phys. 39 4575).