Single Photon-Induced Symmetry Breaking of H ₂ Dissociation

TLDR

H₂ possesses a perfectly symmetric ground state, and symmetry‑breaking mechanisms are applicable to all molecules. The study seeks to determine what is required to break this symmetry. Absorption of a linearly polarized photon entangles symmetric and antisymmetric H₂⁺ states, breaking inversion symmetry and causing asymmetric dissociation into H⁺ and H fragments.

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? We found 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 lack of symmetry results from the entanglement between symmetric and antisymmetric H + 2 states that is caused by autoionization. The mechanisms behind this symmetry breaking are general for all molecules.