Vibrationally-dependent molecular dynamics in mutual neutralisation reactions of molecular oxygen ions.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41006316.
- Also identified by DOI 10.1038/s41467-025-64198-0 and PMC identifier 12474973.
- Licence recorded as CC BY.
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Abstract
Product distributions and dynamics of low-collision-energy mutual neutralisation reactions involving even simple molecular ions are largely unknown. Reactions which involve oxygen ions, e.g., <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> with O<sup>-</sup>, are expected to be important in atmospheric phenomena such as sprites and in high-pressure air or oxygen discharges. Here we show, by combining cryogenically stored-and-merged ion beams with coincident product-imaging techniques, that the <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> with O<sup>-</sup> mutual neutralisation reaction results predominantly in dissociation of the <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> molecule. Three competing reaction pathways yields both O(<sup>3</sup>P) (84%) and O(<sup>1</sup>D) (16%) products, but no O(<sup>1</sup>S) products. Analysis of the momentum-correlated dynamics of the reaction reveals the dominance of two-step mechanisms involving the 3pλ<sub>u</sub> and 3sσ<sub>g</sub> Rydberg states of O<sub>2</sub>. Furthermore, use of the <sup>16,18</sup> <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> isotopologue shows that the reaction products strongly depend on the vibrational levels of the <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>O</mi></mrow> <mrow><mn>2</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> ion for the channel leading to two O(<sup>1</sup>D) products.