Senftleben-Beenakker Effects, Nonresonant Absorption and Collision Integrals for Gases Consisting of Symmetrie Top Molecules

The kinetic theories of the electric and magnetic Senftleben-Beenakker effects and of non­ resonant absorption in polar symmetric top gases are reviewed, using an expansion of the distribu­ tion function-density m atrix which includes the dipole moment operator juQ . General expressions are given for the elastic parts of all collision integrals coupling two purely angular momentum de­ pendent tensors. This is done for a variety of nonspherical potentials, including the dipole-dipole (DD), dipole-quadrupole (DQ) and quadrupole-quadrupole (QQ) interactions. Model calculations for the methyl halogenides are performed for these potentials for a number of collision integrals, namely the nonresonant cross section and three collision cross sections which are of importance for the shear viscosity Senftleben-Beenakker effects. These calculations indicate that DD, DQ and QQ interactions may all be important, that at least half of the nonresonant cross section is elastic and that the average cross section extracted by means of Levi’s theory from electric field shear viscosity Senftleben-Beenakker measurements is approximately equal to the reorientation cross sec­ tion for the tensor polarization [yUe] (2>-