Refractive Index Measurement Method Research Articles

Determination of Order of Molecular Arrangement and Polarizability of Cholesteryl Nonanoate

Abstract Liquid crystals may be subdivided into nematic, cholesteric and smectic classes. Many investigations of the order of arrangement in nematic liquids are reported in the literature,1–6 e.g. for p-azoxyanisole,2 4,4,′-Di-methoxyazoybenzol.5 However, the order of arrangement in cholesteric liquids has not been investigated. Among the methods for determining the order of the molecular arrangement, investigations of birefringence, dichroism, proton resonance,2 magnetic compliance and IR and UV light absorption are the most frequently used.2.7 In recent years the birefringence in cholesteric layers has been observed and measured.8.9 This made possible the determination of the principle refractive indices not only for the liquid crystalline state but also for the solid state. The method of refractive index measurement could be, therefore, applied to calculations of the order of arrangement and principal polarisability coefficients of the molecules forming the cholesteric phase.

An accurate visual method for refractive index measurement in near infrared

A convenient visual technique is described for the refractive index measurement of optical glasses in the near infrared region from 0.7-1.2 mu m. The instrument used is essentially a modification of the Askania high precision spectrometer, incorporating an attachment to convert infrared images into visible ones. A monochromator has been built for the selection of different wavelengths in the near infrared region. Measurements were carried out for three prisms of different glasses employing a minimum deviation method. Accuracy attained is to the fifth decimal place.