Single and Double Scattering Mechanisms in Ionization of Helium by Electron Vortex Projectiles

TL;DR

This study investigates how electron vortex projectiles ionize helium, revealing differences in scattering mechanisms and angular distributions compared to non-vortex electrons, with implications for experimental detection.

Contribution

It introduces a detailed analysis of single and double scattering mechanisms in helium ionization by electron vortex projectiles using distorted wave Born approximation.

Findings

Vortex projectiles can emit electrons into the azimuthal plane without double scattering.

Double scattering remains significant at higher energies for vortex projectiles.

Vortex projectiles cause broadening and splitting of the binary peak in the TDCS.

Abstract

Triple differential cross sections (TDCSs) for electron vortex projectile ionization of helium into the azimuthal plane are calculated using the distorted wave Born approximation. In this collision geometry, the TDCSs at low and intermediate energies exhibit unique qualitative features that can be used to identify single and double scattering mechanisms. In general, our results predict that the ionization dynamics for vortex projectiles are similar to those of their non-vortex counterparts. However, some key differences are observed. For non-vortex projectiles, a double scattering mechanism is required to emit electrons into the azimuthal plane, and this mechanism becomes more important with increasing energy. Our results demonstrate that for vortex projectiles, emission into the azimuthal plane does not require a double scattering mechanism, although this process still significantly influences the shape of the TDCS at higher energies. At low projectile energies, non-vortex ionization proceeds primarily through single binary collisions. The same is generally true for vortex projectiles, although our results indicate that double scattering is also important, even at low energy. Vortex projectiles have an inherent uncertainty in their incident momentum, which causes a broadening of the binary peak at all energies and results in a splitting of the binary peak at higher energies. The results presented here lead to several predictions that can be experimentally tested.