Flow birefringence in gases of linear and symmetric top molecules

Gradients in the stream velocity of a gas consisting of optically anisotropic molecules give rise to an alignment of rotational angular momenta. This alignment can be observed as a birefringence in the gas. The results of such measurements are reported in this paper and interpreted within the framework of a kinetic theory based on the Waldmann-Snider equation. A comparison is made with data obtained from other experiments such as the Senftleben-Beenakker effect and the depolarized Rayleigh scattering.