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.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
