Asymmetric branching ratio for the dissociation of HD+ (1s sigma) - art. no. 062707

Single ionization of the HD molecule by fast ion impact is used to populate the vibrational continuum of the HD+ electronic ground state (1s sigma). T he resulting dissociation leads to two final states, the lower 1s sigma sta te or the first excited 2p sigma state, which is 3.7 meV higher at the sepa rated atom limit due to the finite nuclear mass correction to the Born-Oppe nheimer approximation. We find dissociation to the lower H+ + D(1s) state t o be about 7% more likely than to the upper H(1s) + D+ final state. The maj or experimental difficulty in this measurement is the determination of the H-2 contamination in the HD target. Two different methods of determining th is contamination are presented, and the details of the measurement of the r elative yields of the final two ground-state dissociation channels are disc ussed. The experimental results are compared to our coupled channels calcul ation and to a model based on Meyerhof's approximate formulation.