INELASTIC F-H-2 SCATTERING

We present a first experimental study of inelastic, rotational excitat ion cross-sections in a reactive collision. By preliminary model calcu lations we show that these measurements provide an ideal method for pr obing the anisotropy in the rate-determining entrance-channel valley o f the potential-energy surface for the F-H-2 reaction. A comparison wi th the non-reactive Ne-D2, H-2 scattering system reveals the importanc e of a surprisingly large fourth-order Legendre term in the anisotropi c expansion of the F-H-2 potential. This particular shape feature is r elated to the incipient chemical reaction and is absent in the more el lipsoidal shape of non-reactive potentials for rare gas-H-2 systems.