Second virial coefficient of gaseous HF and rotational inelastic scattering for HF-HF collisions
A recently determined intermolecular potential for HF has been used to calculate the second virial coefficient of the gas in the temperature range 275-9000 K and the rotational inelastic cross sections for HF-HF collisions at a collision energy of 300 cm-1. The virial coefficients calculated in the temperature range 292·5-329 K are in better agreement with an empirical estimate made by Redington than values calculated from other potentials. We have shown that at least seven terms in the bipolar expansion of the potential are necessary to obtain converged scattering cross sections. However, computational limitations have prevented us from concluding that even the seven term expansion has fully converged. We predict large cross sections for transitions which are dipolar coupled (for example (0, 0) →(1, 1)) and some that are not (for example (0, 1) →(1, 1)). The transition (0, 0) →(0, 2) is predicted to have a very small cross section.