The role of surface corrugation in the rotational rainbow scattering of NO from Ag(111)

We report the results of quantum calculations taking explicitly into account the surface corrugation in hyperthermal collisions of NO(X (II)-I-2) with Ag(lll). Our study is based on the potential-energy surfaces of DePristo and Alexander [J. Chem. Phys. 94, 8454 (1991)]. Parallel momentum transfer is found to be substantial. In addition, inclusion of the corrugation strongly attenuates the interference structures due to the rotational rainbows at either low or high angular momentum J. With a single direction of corrugation along the rigid surface and a rotationally cold (J less than or equal to 3/2) incident beam, a Boltzmann plot of the final J distribution no longer exhibits a sharp oscillatory behaviour, in qualitative agreement with the measurements of Rettner, Kimman, and Auerbach [J. Chem. Phys. 94, 734 (1991)]. Notably, the low-J rainbow vanishes. This quenching effect has often been attributed to the large energy transfer with the surface:occurring in the experiments, and/or to the initial state distribution. Thus, the attenuation due to the surface corrugation, although predictable, is far more efficient at damping the quantum oscillations than expected. (C) 1998 American Institute of Physics.