Doubly differential ionization cross sections of proton-helium collisions

We present an investigation of the four-body proton-helium differential scattering problem using the two-center wave-packet convergent close-coupling (WP-CCC) approach. The approach uses correlated two-electron wave functions for the helium target. Here, we focus on doubly differential cross sections for ionization in the intermediate energy (50-300 keV) region where coupling between various channels is important. The greatest difficulty in calculating these cross sections is in representing the final electronic state as the ejected electron travels in the long-range Coulombic fields of both the projectile and the residual target. This state is challenging to take into account. Therefore, available theoretical approaches rely on low-order approximations. Furthermore, there are no comprehensive investigations of all three types of doubly differential cross sections. Our aim is to provide a complete doubly differential picture of ionization and, thereby, fill this gap. We report results for the cross sections differential in any two variables out of three: the projectile scattering angle, the electron ejection angle and energy. Preliminary calculations suggest that the WP-CCC method agrees well with experimental data for all three types of the doubly differential cross sections.