Symmetry breaking in the body-fixed electron emission pattern due to electron-retroaction in the photodissociation of H2+ and D2+ close to threshold

Abstract

We present an experimental investigation of symmetry breaking of H 2 and D 2 molecules after single photoionization due to the Coulomb field of the emitted slow electron interacting with the parent cation during dissociation. The experiments were carried out by measuring the three-dimensional momentum vectors of the photoelectron and recoiling ion in coincidence using a reaction microscope. For photon energies close to threshold, the low-energy photoelectron influences the dissociation process, which results in an asymmetric molecular frame photoelectron angular distribution. This can be explained by the retroaction of the Coulomb field of the photoelectron on its parent ion and has been recently experimentally demonstrated by M. Waitz et al. [Phys. Rev. Lett. 116, 043001 (2016)], confirming theoretical predictions by V. V. Serov and A. S. Kheifets [Phys. Rev. A 89, 031402(R) (2014)]. High-momentum resolution and a new series of photon energies just above the dissociation threshold enable the observation of a strong influence of the electron energy and nuclear kinetic energy on the electron localization process for energies below ∼100 meV, which so far has neither been observed nor discussed by theory. Exploring the limitations of the retroaction mechanism at our lowest photon energy, we are able to single out a sensitive testbed and present data of non-Born-Oppenheimer dynamics of the simplest molecular system for future benchmark computational treatments.

Single-photon induced symmetry breaking of the electron localization and photoelectron directional emission in the dissociative ionization of H2

“…By changing σ from 10 to 50 gradually, the asymmetry parameters keep unchanged. The conclusion is different from the conclusions in [44][45][46][47], where the photoelectron energy is about 2 eV and thus the photoelectron may interact with another bound electron in a relatively long time. In this paper, the photoelectron energy is around 20 eV so that it quickly flies away and the effect of electron-electron repulsion on the final state can be neglected.…”

“…Serov and Kheifets [44] predicted that after single ionization of H 2 , the Coulomb interaction between the freed electron and the vibrating H + 2 may pump H + 2 from the 1sσ g state to the 2pσ u state, making the bound electron preferentially locate on the nucleus moving oppositely to the photoelectron. Later, Waitz et al [45] and Heck et al [46] experimentally observed this asymmetric distribution and confirmed such dynamics. Wang et al [47] used the reduced-dimensionality numerical model to simulate such a process and the simulation results can quantitatively explain the experimental measurement, ensuring the feasibility of such a reduced-dimensionality numerical model.…”

Ultrafast temporal evolution of interatomic Coulombic decay in NeKr dimers

“…30,55 The nuclear dynamics of the ICD process can be described by propagating wave packets on the PECs of the initial and nal ICD states. In our calculations, we assume that the ionization step is instantaneous (sudden approximation), and we neglect the polarization caused by the slow photoelectron 56,57 and the interactions between the initial and nal ICD states similar to previous calculations of ICD dynamics. 58,59 Following these assumptions, the time evolution of the wave packets of the decaying and nal states can be described by the following set of time-dependent Schrödinger equations:…”