  We demonstrate an ion shuttling technique for high-resolution control of
atom-ion collision energy by translating an ion held within a radio-frequency
trap through a magneto-optical atom trap. The technique is demonstrated both
experimentally and through numerical simulations, with the experimental results
indicating control of ion kinetic energies from $0.05-1$ K with a fractional
resolution of $\sim10$ and the simulations demonstrating that kinetic energy
control up to $120$ K with a maximum predicted resolution of $\sim100$ is
possible, offering order-of-magnitude improvements over most alternative
techniques. Lastly, we perform a proof-of-principle chemistry experiment using
this technique and outline how the method may be refined in the future and
applied to the study of molecular ion chemistry.
