DIELECTRIC RELAXATION OF SOME NEARLY SPHERICAL MOLECULES IN THE LIQUID AND SOLID PHASES

Abstract

The dielectric constant and loss at a microwave frequency of 9 GHz and also the static dielectric constant at either 10 kHz or 200 kHz have been measured for the nearly spherical molecules Br3CNO2, Cl3CNO2, BrC(CH3)3, ClC(CH3)3, and ClSi(CH3)3 over a range of temperature from below the respective melting point to above this melting point. The measurements combined with the tabulated values for the optical index of refraction allow a determination of the dielectric relaxation times at each temperature if it is assumed that either the Debye theory or the modification of this theory by Cole and Cole is valid. In the cases of the five liquids, the data are consistent with the Debye model. In the solid phase, however, only Cl3CNO2 and ClSi(CH3)3 do not exhibit solid rotator phases, while each of the other three molecules exhibits at least one solid rotator phase. The results are consistent with the interpretation that each liquid has a single dielectric relaxation time but that the transition to a solid rotator phase involves a distribution of relaxation times which are only slightly different in value from the appropriate single value in the liquid phase.