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Refractive indices of liquid crystals and pure fluids near phase transitions Palffy-Muhoray, Peter

Abstract

Interferometric measurements to determine the refractive indices of the nematic liquid crystals EBBA and BEPC as a function of temperature are described utilizing modified Rayleigh and conoscopic interferometers. Theory is presented relating the refractive indices and density to the orientational order, local field parameter and molecular properties. The results of simple thermal expansivity measurements are also given for EBBA. The Lorentz-Lorenz coefficient for SF₆, and GeH₄, has been determined from refractive index and density measurements. The method utilizes a prism shaped high pressure cell which can be removed from a temperature controlled holder and weighed on a precision balance. The results indicate a variation of 0.5% for SF₆, and 0.8% for GeH₄, over the density range covered.

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