Ionization of helium by antiprotons: Fully correlated, four-dimensional lattice approach

The single ionization of helium by antiproton impact has been studied utilizing a fully correlated, planar model in which the time-dependent Schr\"odinger equation was solved on a four-dimensional (4D) Cartesian lattice. The choice of a ``softcore'' Coulomb potential was shown to enable approximate reproduction of the full six-dimensional p̄He adiabatic electronic eigenenergy curves in the dynamically important region of the 4D space, thus providing a reasonable model to treat p̄+He collisions. In addition, the applicability of this approach was demonstrated by favorable comparison of analogous two-dimensional lattice solutions for ionization of atomic hydrogen by antiprotons with previously computed three-dimensional lattice results. The present work aids in the interpretation of existing theoretical and experimental studies considering the low-energy behavior of the single-ionization cross section for antiproton impact of few-electron targets and explores the applicability of the planar model in describing correlated two-electron systems.