We report on the reactive scattering of methyl iodide,
CH3I, 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 CH3I, 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.