On the internal field correction in far ]infrared absorption of highly polar molecules in neat liquids and dilute solutions

Abstract

Far-infrared absorption spectra for liquid acetone, methylene chloride, acetonitrile, methyl iodide, and their dilute solutions in cyclohexane at 20?C are measured by molecular laser spectrometer. Measurements of dielectric loss of polar liquids and solutions in the frequency range 2-300 GHz are made using a number of different techniques. These two sets of measurements are combined with those made using a Fourier transform spectrometer in order to cover the frequency range up to 250 cm -I and total integrated absorption intensities are calculated. It is shown that the discrepancy between experimental integrated absorption and the theoretical results given by Gordon's sum rule with the Polo-Wilson internal field factor can be explained in the context of Bossis' theory. This theory gives a better agreement with the experimental integrated absorption intensity for these liquids.