Single Photon-Induced Symmetry Breaking of H ₂ Dissociation

Abstract

H 2 , the smallest and most abundant molecule in the universe, has a perfectly symmetric ground state. What does it take to break this symmetry? Here we show that the inversion symmetry can be broken by absorption of a linearly polarized photon, which itself has inversion symmetry.In particular, the emission of a photoelectron with subsequent dissociation of the remaining H + 2 fragment shows no symmetry with respect to the ionic H + and neutral H atomic fragments. This result is the consequence of the entanglement between symmetric and antisymmetric H + 2 states resulting from autoionization. The mechanisms behind this symmetry breaking are general for all molecules.

Exploring few-photon, few-electron reactions at FLASH: from ion yield and momentum measurements to time-resolved and kinematically complete experiments

“…In excellent agreement with the ab initio calculations and previous measurements for one photon single ionization [111] all relevant fragmentation pathways, like ground-state dissociation (maximum at E KER = 0), dissociation via the 2pπ u channel (E KER ≈ 9 eV) as well as contributions and interferences involving the decay of doubly excited (Q2) states [109] are well resolved (Fig. 9a), providing a sound basis for the understanding of TPDI.…”

Molecular ionization and dissociation using synchrotron radiation and ultrashort laser pulses

“…Because in molecules the excess photon energy can be distributed among internal nuclear and electron degrees of freedom however, the situation is much more complex than in atoms, and a clearcut proof of the interference effects is missing. In a very recent work [11], it has been clearly demonstrated that such interference effects cause symmetry breaking in dissociative photoionization. A first observation of asymmetric photoelectron emission from H 2 has been reported in pioneering experiments by Lafosse et al [81].…”

“…Thus regions I and II cannot be the result of a single-step direct photoionization. They are the fingerprint of a delayed emission of an Auger electron from H 2 doubly excited states (either Q 1 or Q 2 [11]). These states can either dissociate due to the repulsive character of the corresponding potential energy curve or decay by autoionization into the 2pσ u or 1sσ g states when such a decay is faster than the time required for an effective dissociation.…”

“…In early pictures of molecular ionization, the nuclear motion was either ignored or described in terms of the Franck-Condon (FC) approximation, in which electronic processes occurring at the equilibrium position of the nuclei are weighted by the squared overlap between the initial and final vibrational states. With the advent of kinematically complete experiments [3,4], in which the momenta of all charged particles is determined, new phenomena with an intrinsic molecular origin have been discovered (see, e.g., [5][6][7][8][9][10][11]). Also the above pictures have been revealed to be incomplete.…”

Ab-<i>initio</i> studies of adsorbate-surface interactions

“…Likewise that TISE, accurate solutions of the TDSE are rare and available only for very simple cases. 40 A time-dependent study of an atom interacting with a surface seems to be a natural continuation of the TM clusters on Gr problem. However, this problem has to overcome two conceptual physical challenges.…”