Examination of Two Theories for Absorption of Microwave and Far Infrared Radiation by Polar Liquids

Abstract

The far infrared spectra of twenty polar organic liquids have been obtained using a cube interferometer spectrometer. Some new liquids have been examined and some of the previously studied liquids have been re-examined over a wider frequency range and the integrated absorption of the broad band with its peak absorption frequency below about 100 cm−1 evaluated, while any contribution from any overlapping higher frequency band has been subtracted. In general, this has not been taken into account in previous such work. Two approaches which have been previously examined to account for the far infrared absorption of such liquids have been tested for a wider variety of liquids and neither mechanism appears to explain quantitatively the observed absorption intensities. Thus the absorption cannot be accounted for by a simple rotational type of mechanism based on Gordon's equation, plus a contribution similar to that which is found in a non polar liquid as has been suggested earlier. In addition, the parameters of the continuous distribution function approach do not match up to those determined experimentally.