Exploring Low Energy Molecular Ion Reactions With Merged Beams

摘要

Charge transfer (CT) in molecular ion-neutral interactions can proceed through dynamically coupled electronic, vibrational, and rotational degrees of freedom. Using the upgraded Oak Ridge National Laboratory ion-atom merged-beams apparatus, absolute direct charge transfer is explored from keV/u collision energies where the collision is considered "ro-vibrationally frozen" to sub-eV/u collision energies where collision times are long enough to sample vibrational and rotational modes. Our first molecular ion measurement with the merged-beams apparatus has been performed for D_(2)~(+) + H and is used to benchmark high energy sudden approximation theory and vibrational specific adiabatic theory for the (H_(2)-H)~(+) complex. CT measurements have also been performed for D_(3)~(+) + H from 2 eV/u to 2 keV/u and CO~(+) + D from 20 eV/u to 2000 eV/u. With straightforward improvements to the apparatus, we plan to extend our measurements to key "destructive" rate coefficients for H_(2)~(+) and CH~(+) with H at temperatures relevant to the interstellar medium.