INELASTIC F-H-2 SCATTERING

We present a first experimental study of inelastic, rotational excitation cross-sections in a reactive collision. By preliminary model calculations we show that these measurements provide an ideal method for probing the anisotropy in the rate-determining entrance-channel valley of the potential-energy surface for the F-H-2 reaction. A comparison with the non-reactive Ne-D2, H-2 scattering system reveals the importance of a surprisingly large fourth-order Legendre term in the anisotropic expansion of the F-H-2 potential. This particular shape feature is related to the incipient chemical reaction and is absent in the more ellipsoidal shape of non-reactive potentials for rare gas-H-2 systems.