Electron Localization in DissociatingH2+by Retroaction of a Photoelectron onto Its Source

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 the case of the H_{2}^{+} dissociating along the 1sσ_{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}^{+}.

The hydrogen molecule under the reaction microscope: single photon double ionization at maximum cross section and threshold (doubly differential cross sections)

“…Such electrons can even retroact. This was for instance observed in the single ionization and subsequent dissociation of H2 [85]. In this case the proton trajectory is influenced by the presence of the long-range Coulomb potential of the retroacting electron.…”

H2: the benchmark molecule for ultrafast science and technologies

“…In this case, the detection integrates over the total outcome. However, a different route to asymmetry in the reaction products has been also taken over the last decade [17,65,77,153,156,189,190]: rather than asymmetric excitation combined with symmetric detection, a symmetric excitation together with an asymmetric detection mechanism becomes possible by taking advantage of the ultimate strengths of electron-ion coincidence techniques. When studying electrons and ions in coincidence, one can fix the direction of the departing electron with respect to the left behind hydrogen and proton and thus has access to the molecular frame and the ability to detect this naturally occurring asymmetry.…”

“…Hence, the reconstruction of the molecular frame from coincidence detection of the ionization fragments lends itself to photoionization with either synchrotron radiation [189], single photon excitation [17], symmetric, circularly polarized laser fields [65,153,156], symmetric, linearly polarized laser fields [77], or the retroaction of the transient field of the photoelectron by Waitz et al [190]. The latter work is based on the theory work by Serov et al [191] stating that the retroaction of a photoelectron might be capable of breaking the symmetry on which side of the remaining + H 2 ion the bound electron localizes: this asymmetry is induced by the transient field of photoelectrons of very low energy.…”

“…In this special case, the steps of ionization and dissociation can no longer be separated. Experimentally, it was observed that the remaining bound electron preferentially localizes on the site opposite to the ejected electron [190].…”

Time-dependent renormalized-natural-orbital theory applied to laser-drivenH2+

“…For comparison also the exact TDSE result is plotted. [43], bond hardening or vibrational trapping [44], chargeresonance-enhanced ionization [45], and the "retroaction" due to the long-range Coulomb potential [46]. We want to further benchmark TDRNOT by investigating its ability to describe non-perturbative phenomena far from equilibrium.…”