Continuum distorted wave theory for positronium formation reactions

The formation of ground-state positronium in collisions of positrons on hydrogen atoms is considered. In previous theoretical works, two-center distorted wave functions were employed to approximate either the initial or the final channel. Here we report results obtained by means of the eikonal final state-continuum distorted wave (EFS-CDW) approximation for which asymptotically correct distorted wave functions are used for both the initial and final states of the scattering system. Comparison of the present theoretical total cross sections with experimental data reveals that distortion effects become important in both channels as the impact energy decreases. This work also shows that the EFS-CDW model is suitable for capture process in the scattering system at unexpected low energies.