Imaging the Atomistic Dynamics of Single Proton Transfer and Combined Hydrogen/Proton Transfer in the O-+CH3I Reaction

We report on reactive scattering studies of the proton transfer and combined hydrogen/proton transfer in the O- + CH3I reaction. We combine state-of-the-art crossed-beam velocity map imaging and quantum chemistry calculations to understand the dynamics for the formations of the CH2I- + OH and CHI- + H2O products. The experimental velocity-and angle-differential cross section show for both products and at all collision energies (between 0.3 and 2.0 eV) that the product ions are predominantly forward scattered. For the CHI- + H2O channel, the data show lower product velocities, indicative of higher internal excitation, than in the case of single proton transfer. Furthermore, our results suggest that the combined hydrogen/ proton transfer proceeds via a two-step process: In the first step, O- abstracts one H atom to form OH-, and then the transient OH- removes an additional proton from CH2I to form the energetically stable H2O coproduct.

Automated summary

In this study, we report on reactive scattering studies of proton transfer and combined hydrogen/proton transfer in the O- + CH3I reaction. State-of-the-art experimental techniques and quantum chemistry calculations were used to understand the dynamics of product formations. The results show that the product ions are predominantly forward scattered and the combined hydrogen/proton transfer channel exhibits lower product velocities compared to single proton transfer.