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On the measurement of the orientational order parameters in biaxial liquid crystals using the polarised infrared technique

Gorkunov, M.V. and Osipov, Mikhail (2010) On the measurement of the orientational order parameters in biaxial liquid crystals using the polarised infrared technique. Liquid Crystals, 37 (12). 1569 - 1576. ISSN 0267-8292

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Abstract

The limits of the applicability of the Polarised Infrared (Fourier transform infrared) spectroscopy technique, which is used to measure the order parameters of biaxial liquid crystals, is investigated in detail for different experimental geometries and cell thicknesses. General expressions for the transmittance of the polarised infrared radiation by a biaxial liquid crystal material in planar and homeotropic cells are obtained in the general case of oblique incidence. These expressions are then simplified in the limiting cases of thin and thick cells, and in both cases the relationship is established between the cell transmittance and the components of the imaginary part of the infrared molecular permittivity. It is shown that simple expressions, used in the literature to extract the values of the biaxial order parameters, are valid only for thin cells and in specific geometries when light propagates along one of the optical axes of the material. For thicker cells typical for experimental conditions, approximate expressions are obtained which are to be used to reveal the order parameters of biaxial liquid crystals. Various types of experimental geometries are discussed including those suitable for measurements of the order parameters, and those to be avoided

Item type: Article
ID code: 29580
Keywords: biaxial order parameters , infrared spectroscopy, biaxial nematics, theory, Probabilities. Mathematical statistics, Materials Science(all), Chemistry(all), Condensed Matter Physics
Subjects: Science > Mathematics > Probabilities. Mathematical statistics
Department: Faculty of Science > Mathematics and Statistics
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Depositing user: Pure Administrator
Date Deposited: 29 Mar 2011 16:40
Last modified: 05 Sep 2014 07:57
URI: http://strathprints.strath.ac.uk/id/eprint/29580

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