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 a ccount the surface corrugation in hyperthermal collisions of NO(X (II) -I-2) with Ag(lll). Our study is based on the potential-energy surface s 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 r otationally cold (J less than or equal to 3/2) incident beam, a Boltzm ann plot of the final J distribution no longer exhibits a sharp oscill atory behaviour, in qualitative agreement with the measurements of Ret tner, Kimman, and Auerbach [J. Chem. Phys. 94, 734 (1991)]. Notably, t he low-J rainbow vanishes. This quenching effect has often been attrib uted to the large energy transfer with the surface:occurring in the ex periments, and/or to the initial state distribution. Thus, the attenua tion due to the surface corrugation, although predictable, is far more efficient at damping the quantum oscillations than expected. (C) 1998 American Institute of Physics.