Close-Coupling and Coupled States Scattering Calculations Applied to Collisions of Methane With Rare Gases
Close-coupling and coupled states scattering calculations are applied to helium methane and neon-methane collisions. State-to-state and total differential cross sections calculated in the coupled states approximation are found to be in at least rough qualitative agreement with the close-coupling results, making the coupled states approximation a useful tool for analyzing particular scattering systems. The theoretical cross sections are compared to experimental measurements and are found to agree in part. The close-coupling calculations of helium-methane scattering show that some disagreements which are observed between the measured helium-methane differential cross sections and coupled states calculations cannot be due to the coupled states approximation. The close coupling calculation of neon-methane scattering and the failure of a thorough search for a neon-methane interaction potential which will fit theory fully to experiment show that disagreements which are observed between the measured neon-methane differential cross sections and coupled states calculations can be due neither to the coupled states approximation nor to the interaction potential. Comparison the results of coupled-states calculations which include closed rotational channels to the results of calculations which neglect them show that these closed channels have a slight influence on the calculated cross sections. The neglect of vibrational closed channels is suggested to be a possible source of disagreement between theory and experiment.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign