Classical trajectory calculation of transport and relaxation properties of O₂-He, Ne mixtures

Abstract

Accurate classical trajectory calculations have been carried out to assess the quality of two O₂-He and two O₂-Ne potential energy surfaces. The four potential energy surfaces have been obtained originally from the inversion of molecular beam scattering data and a limited selection of transport property data. In all four cases the transport property data were analysed using the infinite-order sudden approximation for the scattering dynamics, combined with first Chapman-Cowling approximation expressions for the transport coefficients. The present analyses employ considerably more accurate classical trajectory calculations for the scattering dynamics, together with Chapman-Cowling second approximation expressions for the transport coefficients. The higher level of approximation is clearly seen to be necessary at the present level of comparison. Moreover, the present analyses also examine a number of relaxation and field-effect phenomena (which are very much more sensitive to the anisotropic nature of the potential energy surfaces than are the ordinary transport phenomena), including pressure-broadening of the magnetic dipole-allowed and rotational Raman spectral lines of O₂. For each interaction only one of the two potential surfaces examined is found to agree well with all the non-equilibrium phenomena presently examined. For the O₂-He interaction the potential of Faubel et al. and for the O₂-Ne interaction, the potential of Beneventi et al. provide the best overall agreement with available experimental data. It is clear that the measurement of additional relaxation and field-effect phenomena for O₂-He, Ne mixtures would be most useful for further delineation between proposed potential energy surfaces for these interactions.

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Notes on contributors

Gregory C. Corey

NSERC of Canada University Research Fellow.