Symmetry-breaking dynamics of a photoionized carbon dioxide dimer.

Livshits, Ester; Bittner, Dror M; Trost, Florian; Meister, Severin; Lindenblatt, Hannes; Treusch, Rolf; Gope, Krishnendu; Pfeifer, Thomas et al. · Nat Commun · 2024

basic_science · Level V

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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 <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup> <mrow> <mfenced><mrow><mi>C</mi> <msub><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> </mfenced> </mrow> <mrow><mn>2</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> 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<sub>2h</sub>) geometry of the neutral <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>C</mi> <msub><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> </msub> </math> dimer towards a T-shaped (C<sub>2v</sub>) structure on the ~100 fs timescale, although the most stable slipped-parallel (C<sub>2h</sub>) structure of the ionic dimer. Moreover, we find that excited states of the ionized <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>C</mi> <msub><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> </msub> </math> dimer can exhibit formation of a <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>CO</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </math> moiety in the <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>C</mi></mrow> <mrow><mn>2</mn></mrow> </msub> <msubsup><mrow><mi>O</mi></mrow> <mrow><mn>4</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> complex that can persist even after a suitably time-delayed second photoionization in a metastable <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>C</mi></mrow> <mrow><mn>2</mn></mrow> </msub> <msubsup><mrow><mi>O</mi></mrow> <mrow><mn>4</mn></mrow> <mrow><mn>2</mn> <mo>+</mo></mrow> </msubsup> </math> dication. Our results suggest that charge asymmetry plays an important role in the ionization-induced dynamics in such dimers that are present in <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>C</mi> <msub><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> </msub> </math> rich environments.