Trajectory studies and sensitivity analysis of rotational energy transfer in gas–surface collisions
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The stochastic trajectory method has been applied to the scattering of CO from an LiF(100) surface. At low surface temperature Ts, the trajectories of the gas molecule exhibited multiple collisions with the surface. The degree of rotational and translational energy accommodation could be related to the residence time at the surface. The residence time of the molecule on the surface was in turn related to a desorption rate constant which had an Arrhenius form with an activation energy which was about one third of the interaction potential well depth. At high Ts most of the trajectories exhibited only one gas-surface collision. In this scattering regime we used stochastic sensitivity analysis (SSA) to obtain first and second order sensitivity coefficients which described how the final rotational and translational energies were coupled to Ts and to the initial rotational and translational energies. At low initial translational energies EiT, we found that the most important effect on the final rotational energy of increasing EiT was the increase of the accommodation of energy between the surface modes and the rotational modes of the molecule. The direct coupling of the translational to rotational modes became dominant only at higher EiT. The energy parameters found at high Ts with the SSA were also found to yield the per collision rate of energy accommodation at low Ts. © 1987 American Institute of Physics.
author list (cited authors)
Smith, C. B., & Lucchese, R. R.