QUASI-CLASSICAL TRAJECTORY STUDIES OF THE H+HI -] HI(UPSILON',J')+H ENERGY-TRANSFER AND EXCHANGE-REACTION AT HIGH COLLISION ENERGY

Quasiclassical trajectory (QCT) studies on two potential energy surfaces representing the H + HI --> HI + H system have been performed to investigate the mechanism for production of rotationally and vibrationally excited HI. The potential energy surfaces differ in the stiffness of the HIH bending potential. The results show that on both surfaces, inelastic T --> V, R and reactive exchange are both important sources of excited HI product at collision energies between 16 and 36 kcal mol-1. However, the detailed rotational- and vibrational-state distributions for the inelastic and reactive channels are sensitive to the bending potential. The QCT-derived partial cross sections obtained using the two potential energy surfaces are compared with actual experimental partial cross sections to determine what features of the potential energy surface are needed to describe the real H + HI interaction. A potential energy surface with a substantial angular dependence is necessary to accommodate the experimental results. The light + heavy-light kinematics of the H + HI collisions impose constraints on the angular momentum coupling in the collisions.