The influence of intermolecular interactions on the Kerr effect in gases

The Kerr effect has been measured over ranges of temperature and pressure for gaseous argon, krypton, xenon, methane, tetrafluoromethane, 2,2-dimethylpropane and sulphur hexafluoride. Measurements have been analysed in terms of a virial expansion for the molar Kerr constant, and values are reported for the first and second Kerr virial coefficients (A K and B K). Tentative results for the third Kerr virial coefficient (C K) have also been obtained for methane, tetrafluoromethane, 2,2-dimethylpropane and sulphur hexafluoride. The temperature independent A K is directly proportional to the second electric dipole hyperpolarizability, while B K and C K depend on the polarizability of interacting pairs and triplets of molecules. Our measurements of B K are compared with those calculated from the DID model (see preceding paper [4]), and a correlation between the ratio B K expt/B K DID and molecular interaction parameters is demonstrated. The results are also compared with measurements of depolarized light scattering in compressed gases.