Electron localization in dissociating $H_2^+$ by retroaction of a photoelectron onto its source

TL;DR

This study demonstrates that in the dissociation of $H_2^+$ after photoionization, the emitted proton preferentially moves in the same direction as the escaping photoelectron, showing a Coulomb-driven symmetry breaking effect.

Contribution

The paper provides experimental evidence supporting a classical model predicting symmetry breaking in $H_2^+$ dissociation due to Coulomb retroaction, confirming recent theoretical predictions.

Findings

Proton ejection direction correlates with photoelectron emission.

Symmetry breaking is most pronounced at low electron energies.

Results align with classical Coulomb retroaction model.

Abstract

We investigate the dissociation of $H_2^+$ into a proton and a $H^0$ after single ionization with photons of an energy close to the threshold. We find that the $p^+$ and the $H^0$ do not emerge symmetrically in case of the $H_2^+$ dissociating along the $1s\sigma_g$ ground state. Instead, a preference for the ejection of the $p^+$ in the direction of the escaping photoelectron can be observed. This symmetry breaking is strongest for very small electron energies. Our experiment is consistent with a recent prediction by Serov and Kheifets [Phys. Rev. A 89, 031402 (2014)]. In their model, which treats the photoelectron classically, the symmetry breaking is induced by the retroaction of the long range Coulomb potential onto the dissociating $H_2^+$.