Asymmetric branching ratio for the dissociation ofHD+(1sσ)

Abstract

Single ionization of the HD molecule by fast ion impact is used to populate the vibrational continuum of the ${\mathrm{HD}}^{+}$ electronic ground state $(1s\ensuremath{\sigma}).$ The resulting dissociation leads to two final states, the lower $1s\ensuremath{\sigma}$ state or the first excited $2p\ensuremath{\sigma}$ state, which is 3.7 meV higher at the separated atom limit due to the finite nuclear mass correction to the Born-Oppenheimer approximation. We find dissociation to the lower ${\mathrm{H}}^{+}+\mathrm{D}(1s)$ state to be about 7% more likely than to the upper $\mathrm{H}(1s)+{\mathrm{D}}^{+}$ final state. The major experimental difficulty in this measurement is the determination of the ${\mathrm{H}}_{2}$ contamination in the HD target. Two different methods of determining this contamination are presented, and the details of the measurement of the relative yields of the final two ground-state dissociation channels are discussed. The experimental results are compared to our coupled channels calculation and to a model based on Meyerhof's approximate formulation.