Rotational energy relaxation of symmetric top molecules by collisions with atoms Original Research Article

The infinite-order sudden approximation has been used to calculate the effective cross sections for R-T energy transfer (σE) of symmetric top molecules by collisions with atoms. In a final form σE is expressed via 〈ΔE2〉 (the mean-square change in rotational energy), which is analytically expressed through the partial phase shifts. A quadratic dependence of σE on phase shifts derived in the present study indicates a very high sensitivity of σE to the details of the anisotropic potential. Within the developed formalism, spherical and linear molecules are treated as the limiting cases. Detailed comparisons between the IOSA values and semiclassical sudden calculations are carried out for rare-gas-SF6 mixtures.