Knowledge Bank

The Monte Carlo method employed by Borenstein and $Lamb1$ has used to calculate one-dimensional classical kernels for collisions. Lennard-Jones and Buckingham-Slater potentials were assumed for the calculations. The resulting kernels have been compared to collision kernels deduced from infrared-infrared double resonance spectra recorded for pure methyl fluoride and for dilute samples of methyl fluoride in hydrogen, helium, argon, and xenon. Although the collisions to the spectra are not elastic and probably not classical, the translational kinetic energy is large compared to the rotational energy transferred by collision and classical collision calculations often give results that provide useful intial comparisons to experimental data. For methyl fluoride-methyl fluoride collisions, the calculated kernels show a strong resemblance to the sums of two Keilson-Storer $kernels2$ that we have used previously fit experimental data for pure methyl fluoride. The calculated kernels also provide a rationalization for the differences seen between the four-level double resonance spectra observed for methyl fluoride-hydrogen and for methyl fluoride-helium as well as the differences seen for methyl fluoride-helium and methyl fluoride-xenon. Finally, the calculated kernels show the ``recoil effect” that has been seen in double resonance spectra involving methyl fluoride and argon or xenon. By contrast, the increase in the change in velocity with increase in mean relative velocity deduced from the double resonance spectra for methyl fluoride-methyl fluoride collisions is not confirmed by the classical calculations.