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 $${\left({{{\rm{C}}}}{{{{\rm{O}}}}}_{2}\right)}_{2}^{+}$$ 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 $${{{\rm{C}}}}{{{{\rm{O}}}}}_{2}$$ 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 $${{{\rm{C}}}}{{{{\rm{O}}}}}_{2}$$ C O 2 dimer can exhibit formation of a $${{{{\rm{CO}}}}}_{3}$$ CO 3 moiety in the $${{{{\rm{C}}}}}_{2}{{{{\rm{O}}}}}_{4}^{+}\,$$ C 2 O 4 + complex that can persist even after a suitably time-delayed second photoionization in a metastable $${{{{\rm{C}}}}}_{2}{{{{\rm{O}}}}}_{4}^{2+}$$ 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 $${{{\rm{C}}}}{{{{\rm{O}}}}}_{2}$$ C O 2 rich environments.