Fivefold differential cross sections for the ionization of aligned hydrogen molecule by electron and positron impact

Abstract

We report fivefold differential cross section (5DCS) for the ionization of aligned hydrogen molecule by electron and positron impact in coplanar geometry. The calculations have been performed for an incident energy of 200 eV and ejection energies of (3.5 ± 2.5) and (16 ± 4) eV. The present calculations are based on the eikonal approximation due to Glauber, and the BBK approximation. We have included the effect of post collision interaction (PCI) in the Glauber approximation classically. A comparison is made of the present calculations with the results of other theoretical methods and the recent experiment of Senftleben et al. [ 28]. The present theoretical models predict that the 5DCS is maximum when the intermolecular axis is aligned along the incident beam direction. The binary to recoil peak ratios predicted by the Glauber approximation with PCI (GA-PCI) are in reasonably good agreement with the experiment. The positions of the binary peaks predicted by the BBK approximation are also in good agreement with the experiment. The positron-impact ionization cross sections obtained in the BBK and GA-PCI methods are found to be higher than the electron-impact cross sections in the binary region while the converse is true for the recoil regime. In case of positron impact, the binary peaks predicted by both the GA-PCI and BBK models shifted away from the direction of momentum transfer, and showed a trend which is opposite to the case of electron impact ionization.