Speaker
Description
The feasibility of performing merged beam experiments with trapped fast ion beams of molecular cations and anions at the double electrostatic storage ring (DESIREE) and the hybrid electrostatic ion beam trap (HEIBT),[1,2] opens new opportunities to study mutual neutralization reactions. Here, I will present our findings from merged beam experiments performed at DESIREE on the mutual neutralization of hydronium (H3O+) and hydroxide (OH¯),[3] and their isotopomers.[4] 3D coincidence imaging of the neutral products allowed us to disentangle the different competing proton-transfer and electron-transfer mechanisms. We identified a predominant e-transfer mechanism that forms either one or two OH radicals in a single neutralization reaction. By analyzing measured 3-body momentum correlations, we found that the distance at which the electron transfer occurs determines the final product channel. Figure 1 illustrates the two competing non-adiabatic electron transfer pathways. Electron transfer at a distance of ~4Å (left panel) forms the neutral H3O radical intermediate ground state, which then dissociates into H2O and H. In contrast, electron transfer at ~10Å presented in the right panel forms an electronically excited H3O intermediate that dissociates into H2 and a 2nd OH radical. These mutual neutralization dynamics of the isolated water ions can be related to ion-ion reactions on the liquid water surface and offer an explanation for the recent observations of spontaneous hydrogen peroxide formation in pure water microdroplets.[5-7]
References
1 A. Bogot et al, Phys. Chem. Chem. Phys., 25, 25701-25710 (2023)
[2] H.T. Schmidt et al, Rev. Sci. Instrum., 84, 055115 (2013)
[3] A. Bogot et al, Science, 383, 285-289 (2024)
[4] A. Bogot et al, preprint available at Research Square https://doi.org/10.21203/rs.3.rs-4777257/v1
[5] J.K. Lee et al, PNAS, 116 (39), 19294-19298 (2019)
[6] P. Skurski and J. Simons, J. Chem. Phys., 160, 034708 (2024)
[7] J.P. Heindel et al, Nat Commun, 15, 3670 (2024)
