The viscomagnetic effect in polar gases

Abstract

The magnetic field effect on the viscosity has been measured for several polyatomic gases with the emphasis on symmetric top molecules with strong electric dipoles. Theoretical expressions are given for the field dependent viscosity coefficients for various types of angular momentum polarizations, both for linear and symmetric top molecules. For CO2, OCS, N2O, SF6, CH3F, CHF3, PF3 and NF3 a decrease of the viscosity in a magnetic field was observed, which can be well described on the basis of a single angular momentum tensor polarization of the type . For NH3 and ND3, however, an increase in the viscosity was observed. In this case, a single polarization of the type J is involved. For HCl, DCl, AsH3 and PH3, no effects could be observed (|Δη/η|⩽2×10−5). No simple correlation is found between the magnitude of the effect and the strength of the molecular electric dipole moment. The experimental results are expressed in terms of effevtive cross sections.