Looking for Reaction Complexes in Trapped Ion Reactions of Xe⁺ and O₂⁺ with C₃H₄ Isomers

Ion-molecule reactions play an important role in a variety of environments such as the interstellar medium and the upper ionosphere. Significant progress has been made in understanding the mechanisms that control such reactions, but there is still much to discover. I will present recent work expanding on prior studies of the C₃H₄ isomers allene (H₂C₃H₂) and propyne (H₃C₃H), which have shown isomeric dependence on their reactivities. Specifically, I will discuss our results from reactions of Xe⁺ and O₂⁺ cations with these isomers in a cold ion-trap environment. These ions have nearly identical ionization potentials and thus offer nearly isoenergetic conditions for reactions due to the low level of kinetic energy available. Experimental measurements and theoretical calculations show that the propensity of forming a reaction complex depends not only on the isomeric structure of the neutral C₃H_4, but also on its ionic reaction partner. This expands on what was previously understood about reactions in these systems and offers a more thorough picture of ion-molecule reaction mechanisms._­­­