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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 (CO2)2+ dynamics, that combined with ab initio molecular dynamics simulations, revealed unexpected asymmetric structural rearran- gement. We show that ionization by the pump pulse induces rearrangement from the slipped-parallel (C2h) geometry of the neutral CO2 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 CO2 dimer can exhibit formation of a CO3 moiety in the C2O4+ complex that can persist even after a suitably time-delayed sec- ond photoionization in a metastable C2O42+ dication. Our results suggest that charge asymmetry plays an important role in the ionization-induced dynamics in such dimers that are present in CO2 rich environments.
