Influence of molecular electric quadrupole moments on dielectric constants

Abstract

The effect of a molecular electric quadrupole moment on the dielectric constant of a gas composed of nonpolar molecules is calculated to the lowest order of density and polarizability in which it appears. The quadrupoles induce electric dipoles in neighboring molecules, and these dipoles interact with an applied uniform electric field. The total effect is a deviation from the Clausius-Mosotti equation, proportional to the square of the quadrupole moment, and of the same order of magnitude as the deviation due to fluctuations in dipole moment calculated by Kirkwood, and the deviation due to the variation of polarizability with density calculated by Mazur and Jansen. The theory is tested by calculating the quadrupole moment of CO2 from dielectric constant data. The result is about five times larger than the value obtained by microwave pressure broadening, and is about forty percent larger than the value obtained by Pople from the second virial coefficient of CO2.