Total reflection method, nematics

Dorn [2] performed the first precise measurements of the principal refractive indices rif. and for the N and SmA phases of ethyl-4- [4-ethoxybenzylideneamino]-a-methylcinnamate using Abbe s total reflection method. Also later measurements on nematic liquid crystals by Gaubert [3] and Mauguin [4] were based on the determination of the boundary angle of total reflection. In 1950, Pellet and Chatelain [5] intro-... 

In Abbe s double prism method a thin ho-meotropically oriented nematic film is placed between the hypotenuse faces of two rectangular prisms. Using light polarized parallel and perpendicular to the optical axis, respectively, the principal refractive indices and can be obtained directly from the critical angle of total reflection, provided that the refractive index of the prism is greater than that of the liquid crystal [2, 8-10]. In some cases the director of the nematic phase was oriented uniformly parallel to the prism planes [11-14]. Special variants of the total reflection method have been described [3, 4, 15, 16]. A total reflection refractometer of the Abbe type has also been used to determine n, n and An in the infrared region between 2.5 and 14 p.m [17]. 

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