Symmetry-breaking dynamics of a photoionized carbon dioxide dimer

Photoionization can initiate structural reorganization of molecular matter and drive formation of new chemical bonds. Here, we used time-resolved extreme ultraviolet (EUV) pump – EUV probe Coulomb explosion imaging of carbon dioxide dimer ion ({{{C}}{{{O}}}₂) }₂^+ dynamics, that combined with ab initio molecular dynamics simulations, revealed unexpected asymmetric structural rearrangement. We show that ionization by the pump pulse induces rearrangement from the slipped-parallel (C2h) geometry of the neutral {{C}}{{{O}}}₂ dimer towards a T-shaped (C2v) structure on the ~100 fs timescale, although the most stable slipped-parallel (C2h) structure of the ionic dimer. Moreover, we find that excited states of the ionized {{C}}{{{O}}}₂ dimer can exhibit formation of a {{{CO}}}₃ moiety in the {{{C}}}₂{{{O}}}₄^+\, complex that can persist even after a suitably time-delayed second photoionization in a metastable {{{C}}}₂{{{O}}}₄^2+ dication. Our results suggest that charge asymmetry plays an important role in the ionization-induced dynamics in such dimers that are present in {{C}}{{{O}}}₂ rich environments. In a time-resolved Coulomb explosion imaging study using ultrafast extreme ultraviolet pulses, combined with theoretical simulations, authors reveal unexpected asymmetric rearrangement of carbon dioxide dimer ion, including a CO3 moiety formation.