Low-energy electron capture by Cl{sup 7+} from D using merged beams

Measurements of the absolute total cross section for single-electron capture in collisions of Cl{sup 7+} with ground-state atomic deuterium are reported in the energy range 4.6--428 eV/amu. These measurements represent the highest charge state yet reported using the Oak Ridge National Laboratory ion-atom merged-beams apparatus. The electron-capture cross section for Cl{sup 7+} is observed to decrease at lower energies, in contradiction to what is expected from a popular simple model and speculation from previous measurements for highly charged (7+) ions with multielectron cores. The observed low-energy behavior is interpreted using coupled-channel molecular-orbital hidden-crossing calculations for N{sup 7+}+D.