Symmetry-breaking dynamics of a photoionized carbon dioxide dimer

Abstract

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 ${\left(\mathrm{C}{\mathrm{O}}_2\right)}_2^{+}$ 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 (C_2h) geometry of the neutral $\mathrm{C}{\mathrm{O}}_2$ dimer towards a T-shaped (C_2v) structure on the ~100 fs timescale, although the most stable slipped-parallel (C_2h) structure of the ionic dimer. Moreover, we find that excited states of the ionized $\mathrm{C}{\mathrm{O}}_2$ dimer can exhibit formation of a ${\mathrm{CO}}_3$ moiety in the ${\mathrm{C}}_2{\mathrm{O}}_4^{+}$ complex that can persist even after a suitably time-delayed second photoionization in a metastable ${\mathrm{C}}_2{\mathrm{O}}_4^{2+}$ dication. Our results suggest that charge asymmetry plays an important role in the ionization-induced dynamics in such dimers that are present in $\mathrm{C}{\mathrm{O}}_2$ 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.