Trajectory effects on charge exchange and energy loss in collisions of H$^+$, He$^{2+}$, Li$^{3+}$, and Be$^{4+}$ ions with atomic hydrogen

TL;DR

This study investigates how the trajectory of ions affects charge exchange and energy loss during collisions with atomic hydrogen, revealing trajectory independence for charge exchange but significant effects on energy loss, especially at low energies.

Contribution

It introduces a coupled electron-nuclear dynamics approach to assess trajectory effects, highlighting the importance of nuclear trajectory considerations in collision processes.

Findings

Charge exchange is trajectory-independent across studied energies.

Projectile energy loss depends strongly on trajectory, especially at low energies.

Nuclear energy loss becomes significant at low collision energies due to polarization effects.

Abstract

The charge exchange and energy loss processes provide insights into fundamental processes across physical, chemical, and engineered systems. While this field has been thoroughly investigated, a clear study on trajectory effects is lacking, particularly in the context of inelastic processes at low energies. In this work, we address this gap by solving the time-dependent Schr\"odinger equation for the electron in a numerical lattice with a coupled electron-nuclear dynamics approach as well as a straight-line trajectory approximation for the nuclei to asses trajectory effects on charge exchange and energy loss. The collision dynamics are studied using bare ion projectiles with charge $Z=$1-4 incident on atomic hydrogen in an energy range of 0.1 to 900 keV/u. We find that the charge exchange process is trajectory-independent within the energy range considered, showing excellent agreement with available experimental and theoretical data. However, projectile energy loss exhibits strong trajectory dependence, with the straight-line approximation overestimating energy loss at low collision energies due to the forced linear path. Our results for electronic stopping cross sections with electron-nuclear coupled trajectories are consistent with the available experimental data at high collision energies. At low energies, nuclear energy loss becomes prominent, driven by polarization effects induced by the ion charge on the hydrogen target. Overall, our work highlights the importance of nuclear trajectory considerations in collision dynamics and offers a foundation for further investigations of more complex systems.