2D electron momentum distributions for transfer ionization in fast proton Helium collisions

TL;DR

This study measures and analyzes the two-dimensional electron momentum distributions in transfer ionization during fast proton-Helium collisions, comparing experimental data with theoretical models to understand electron emission mechanisms.

Contribution

It provides detailed experimental measurements of electron momentum distributions and evaluates the effectiveness of the Plane Wave First Born Approximation in explaining observed phenomena.

Findings

Backward electron emission is mainly influenced by electron correlations.

Second order effects are necessary to accurately describe forward electron emission.

Theoretical calculations align with experimental data when including electron correlations.

Abstract

The momentum distribution of the electron in the reaction p+He $\rightarrow$ H + He$^{2+}$ + $e$ is measured for projectile energies $E_p$=300 and 630 keV/u at very small scattering angles of hydrogen. We mainly present two dimensional distributions parallel $(k_{||})$ and perpendicular $(k_{\perp})$ to the projectile beam. Theoretical calculations were carried out within the Plane Wave First Born Approximation (PWFBA), which includes both electron emission mechanisms, shake-off and sequential capture and ionization. It is shown that electron correlations in the target wave function play the most important role in the explanation of experimentally observed backward emission. Second order effects have to be involved to correctly describe the forward emission of the electron.