Agreement at last: an experimental and theoretical study on the single ionization of helium by fast proton impact

TL;DR

This study presents high-resolution experimental data on helium ionization by 1 MeV protons, demonstrating that the first Born approximation accurately predicts the results, resolving longstanding discrepancies between theory and experiment.

Contribution

It provides the first high-resolution experimental validation that the first Born approximation can reliably describe helium ionization by fast protons.

Findings

Good agreement between experiment and first Born approximation

Projectile coherence effects influence electron emission distributions

Supports the validity of simple theoretical models for high-energy ionization

Abstract

Even though ion/atom-collision is a mature field of atomic physics great discrepancies between experiment and theoretical calculations are still common. Here we present experimental results with highest momentum resolution on single ionization of helium induced by 1\,MeV protons and compare these to different theoretical calculations. The overall agreement is strikingly good and already the first Born approximation yields good agreement between theory and experiment. This has been expected since several decades, but so far has not been accomplished. The influence of projectile coherence effects on the measured data is shortly discussed in line with an ongoing dispute on the existence of nodal structures in the electron angular emission distributions.