A semiclassical treatment of rotationally electronically inelastic scattering of NO from Ag(111)

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Abstract
The direct rotationally electronically inelastic scattering of NO from a rigid, uncorrugated Ag(111) surface is studied using the semiclassical self-consistent eikonal method (SCEM). Final rotational state distributions, summed over spin–orbit and Λ-doublet levels, are in good agreement with the exact quantum calculations of Smedley, Corey, and Alexander [J. Chem. Phys. 87, 3218 (1987)]. In addition to reproducing the rotational rainbows at low and high values of the final rotational quantum number J′, the SCEM calculation reproduces fine structure dependence of the final rotational distributions which is sensitive to quantum interference effects. Besides providing a quantitative alternative to fully quantum close coupling, the semiclassical method gives new insight into the dynamics of the collision process. For a translational energy of 6700 cm−1, population of states higher than J′=42.5 is dynamically limited, even though final rotational states up to J′=61.5 are energetically accessible. Similar dynamical constraints are observed for translational energies from 3200 to 10 700 cm−1. The dynamical constraints do not exist at Etot =2500 cm−1, resulting in an overestimation of the rotational excitation by the SCEM calculation. Translational-to-rotational energy transfer has a nonlinear dependence on initial translational energy over an energy range of 2500–10 700 cm−1. Additionally, the location of the high J′ rotational rainbow has a weak dependence on initial translational energy within this energy range. With increasing translational energy, the rotational distribution shifts to higher J′ while the high J′ rotational rainbow shifts to slightly lower J′. Also, the highest rotational state with significant population is only weakly dependent on the initial translational energy. By contrast, at a translational energy of 6700 cm−1, translational-to-rotational energy transfer is strongly dependent on initial rotational energy.