One-photon excitation and dissociation of both weakly bound rotational excited states and vibrational excited states of HD2+ and photofragment branching ratio D+/H+ of the final predissociative states

The presence of weakly bound rotationally excited initial states of HD2+ ly ing just below the lowest dissociation limit has been observed as well as q uasibound, predissociative final states above the dissociation limit result ing from one-photon excitation of those weakly bound states. The excitation of the initial weakly bound and possibly only few quasi-bound states took place with 1064 nm laser radiation. The possibility of one-photon excitatio n of the vibrationally excited initial HD2+ ions is considered. The centre-of-mass kinetic energy distributions of the D+ and H+ fragment w ere used to identify the possible initial and final states involved in the transitions leading to these fragments. The fragment ratio D+/H+ is shown t o be critically dependent on the ion source pressure. A strong preference i s observed for the D+ + HD dissociation channel over the H+ + D-2 channel a t high source gas pressures. The centre-of-mass energy of the resulting H+ and D+ fragments was found to agree with predicted theoretical values, and suggest that among initially excited HD2+ ions, only a few of these lie initially above the lowest disso ciation limit.