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 em-I. 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 X 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.•

Molecular Motions in CCl4: Light Scattering and Infrared Absorption

“…We believe this to be generally true for nonpolar systems. For example, a similar calculation of the absorption shape for CS2 fits the high frequency absorption wing reported by Garg et al 4 very well.…”

“…4. A comparison of the experimental loss tangent with that predicted from the light scattering spectrum.…”

Temperature-Dependent Terahertz Spectroscopy of Liquid n-alkanes

“…The significance of terahertz spectroscopy as a tool for understanding intermolecular dynamics was recognized almost 40 years ago [13]. This is in contrast to more conventional mid-infrared absorption signatures, which arise due to intramolecular modes (e.g., C-C stretch, CH 2 deformation modes), and therefore provide only indirect information about intermolecular motions.…”

The Infrared Spectrum of Ethylene Oxide Clathrate Hydrate between 360 and 20 cm−1, at 100 °K

“…Because of previous experimental results on the far-infrared absorption by non-polar (29) and polar (30) liquids, and considering the dipole moment of ethylene oxide (31), there can be little doubt that most of the absorption intensity will arise from the rotational vibrations, although these are not necessarily distinct from the translational vibrations in this disordered crystal. The experimental results do not dictate the assignment of these vibrations.…”