Near Resonant Charge Transfer in Intermediate-High Energy Collisions between Molecular Ions and Atomic Hydrogen

Using the Oak Ridge National Laboratory (ORNL) ion--atom merged--beams apparatus, absolute cross sections of near resonant direct and dissociative charge transfer (CT) between H/D and different molecular ions (D$_{2}^{+}$, CO$^{+}$, O$_{2}^{+}$, and D$_{3}^{+})$ are measured from 20eV/u to 2keV/u collision energies. Below a few hundred eV/u collision energy, each measured cross section exhibits the dynamics of the vibrational and rotational modes of the molecular ion. Toward high energy collisions where the differences in the Q-value of the reaction can be neglected and the ro--vibrational modes can be considered as frozen, the measured CT cross sections for the diatomic ions increase, lose track of the ro-vibrational mode signatures and all converge to (7.5 $\pm $ 0.5) x 10$^{-16}$ cm$^{2}$ at 2keV/u. The measured CT cross section for the tri-atomic ion D$_{3}^{+}$, which may have only endoergic dissociative CT channels, differs from that of the diatomic ions.