Differential cross sections for the charge transfer reaction between Ar + and CO have been measured using three-dimensional velocity map imaging in a crossed beam setup at the two relative collision energies 0.55 and 0.74 eV. We find dominant forward scattering with CO + product ions predominantly in the vibrational levels ν = 6,7 of the electronic ground state X 2 + . This is indicative of a direct resonant mechanism for the two argon spin-orbit states. At both collision energies also an isotropic distribution with product ions exhibiting high internal excitation is observed. This is more pronounced at the higher collision energy, where the first electronically excited state A 2 + becomes accessible. We conclude that the A-state is partially populated by the product ions at 0.74 eV collision energy and suggest that the isotropic distribution stems from the formation of a charge-transfer complex, in concurrence with previously performed studies.

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.

We report on the reactive scattering of methyl iodide, CH 3 I, with atomic oxygen anions O − . This radical ion− molecule reaction can produce different ionic products depending on the angle of attack of the nucleophile O − on the target molecule. We present results on the backside and frontside attack of O − on CH 3 I, which can lead to I − and IO − products, respectively. We combine crossed-beam velocity map imaging with quantum chemical calculations to unravel the chemical reaction dynamics. Energy-dependent scattering experiments in the range of 0.3−2.0 eV relative collision energy revealed that three different reaction pathways can lead to I − products, making it the predominant observed product. Backside attack occurs via a hydrogen-bonded complex with observed indirect, forward, and sideways scattered iodide products. Halide abstraction via frontside attack produces IO − , which mainly shows isotropic and backward scattered products at low energies. IO − is observed to dissociate further to I − + O at a certain energy threshold and favors more direct dynamics at higher collision energies.

We present infrared predissociation spectra of C2N−(H2) and C 3N−(H2) in the 300–1850 cm−1 range. Measurements were performed using the FELion cryogenic ion trap end user station at the Free Electron Lasers for Infrared eXperiments (FELIX) laboratory. For C2N−(H2), we detected the CCN bending and CC−N stretching vibrations. For the C3N−(H2) system, we detected the CCN bending, the CC−CN stretching, and multiple overtones and/or combination bands. The assignment and interpretation of the presented experimental spectra is validated by calculations of anharmonic spectra within the vibrational configuration interaction (VCI) approach, based on potential energy surfaces calculated at explicitly correlated coupled cluster theory (CCSD(T)‐F12/cc‐pVTZ−F12). The H2 tag acts as an innocent spectator, not significantly affecting the C2,3N− bending and stretching mode positions. The recorded infrared predissociation spectra can thus be used as a proxy for the vibrational spectra of the bare anions.

The competition between the bimolecular nucleophilic substitution (SN2) and base-induced elimination (E2) reaction and their intrinsic reactivity is of key interest in organic chemistry. To investigate the effect of suppressing...