Microwave dispersion of some polar liquids

TLDR: In this paper, an analysis of the microwave dispersion of some polar liquids is presented, and a new microwave measuring technique is described, accurate in most cases to about 1% for both the real and imaginary part of ǫ, where the results refer to wavelengths down to 0.8 cm.

Abstract: The chief purpose of the present investigation is the measurement and analysis of the microwave dispersion of some polar liquids. An outline of the problem and a historical survey of experimental work on the dielectric behaviour of polar liquids are given in Chapter I. A number of theoretical expressions for the dielectric constant in the static case and their extension to alternating fields are reviewed in Chapter II. A formula for the dielectric dispersion in liquids composed of ellipsoidal molecules is derived and its consequences are investigated. Chapter III deals with the experimental details of the investigation. A new microwave measuring technique is described, accurate in most cases to about 1% for both the real and imaginary part of є. In order to make the theories applicable, the investigation has been restricted mainly to polar liquids of simple structure, in particular to the mono-substituted benzenes. The results refer to wavelengths down to 0.8 cm. The analysis of our measurements in Chapter IV reveals discrepancies between the dielectric constant e∞, extrapolated from the side of cm-waves, and n2, the square of the refractive index, extrapolated from measurements in the visible and infrared. This leads to assuming an additional region of dipolar absorption in the neighbourhood of 1 mm. The mechanism to which such an absorption may be due is sought in the strong local fields exerted on a molecule by its immediate neighbours.