BRANCHING AND ANISOTROPY OF BARRIER TUNNELING AND FLUORESCENT DECAY IN H-2 .1. EXPERIMENT

Photodissociation of quasibound levels in the i (3) Pi(g) state of mol ecular hydrogen is studied using fast-beam photofragment spectroscopy. The molecules dissociate either via molecular fluorescence to a repul sive state or by barrier tunneling followed by atomic fluorescence. We measured the branching between the two pathways and the anisotropy of the photofragment distribution. The branching ratios were calculated from the potential-energy curve (see the theoretical treatment given i n the following paper [Phys. Rev. A 54, 531 (1996)]). The observed and calculated branching ratios are found to be in good agreement. Small discrepancies can be accounted for by the electronic mixing with neigh boring states. The photofragment anisotropy is a diagnostic tool for t he dissociation continuum and the lifetime of the excited state. The e xperimentally found anisotropy parameters corroborate the electronic m ixing and also show that the fine and hyperfine structure are resolvab le only for the lowest three rotational levels examined.