Ionization of helium by slow antiproton impact: total and differential cross sections

TL;DR

This study provides detailed theoretical insights into helium ionization caused by slow antiprotons, including total and differential cross sections, with results matching experimental data and revealing new features like the binary-encounter peak.

Contribution

It offers the first fully ab initio doubly differential data for helium ionization by antiprotons at specific energies, advancing understanding of collision dynamics.

Findings

Quantum results agree with experimental data.

First ab initio differential cross sections at 10 and 100 keV.

Identification of binary-encounter peak and anticusp minimum.

Abstract

We theoretically investigate the single and double ionization of the He atom by antiproton impact for projectile energies ranging from $3$~keV up to $1000$~keV. We obtain accurate total cross sections by directly solving the fully correlated two-electron time-dependent Schr\"odinger equation and by performing classical trajectory Monte-Carlo calculations. The obtained quantum-mechanical results are in excellent agreement with the available experimental data. Along with the total cross sections, we also present the first fully \textit{ab initio} doubly differential data for single ionization at 10 and 100~keV impact energies. In these differential cross sections we identify the binary-encounter peak along with the anticusp minimum. Furthermore, we also point out the importance of the post-collisional electron-projectile interaction at low antiproton energies which significantly suppresses electron emission in the forward direction.