Dielectric Relaxation, Far-Infrared Absorption, and Intermolecular Forces in Nonpolar Liquids

Abstract

Measurements of dielectric constant and loss at 2.1-mm wavelength have been carried out upon benzene, cyclohexane, n-heptane, carbon disulfide, carbon tetrachloride, and tetrachloroethylene, and similar measurements at centimeter wavelengths have been carried out where needed. The infrared absorption spectra of the liquids were measured from 17–170 cm−1. The points for dielectric absorption fit on a smooth curve drawn through the infrared absorption points. Similar measurements have been made upon several binary mixtures of these liquids. Measurements upon liquids to which very small quantities of water have been added show that the effect of water can be corrected for or disregarded. Relaxation times calculated from the dielectric constant and loss measurements are close to 1 × 10−12 sec for all of the liquids, which is the magnitude of the time between the collisions of a molecule in the liquid with its neighbors. Apparent dipole moments calculated for the molecules from these measurements are close to 0.1 D and in satisfactory agreement with values of the dipole moments calculated as induced by the quadrupole or octopole moments of neighboring molecules.