Optical measurements of orientational order in uniaxial and biaxial nematic liquid crystals
Optical measurements of orientational order in uniaxial and biaxial nematic liquid crystals
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DOI：
10.1080/02678292.2010.488818
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发表时间：
2010-01-01
期刊：
影响因子：
2.2
通讯作者：
Gortz, V.
中科院分区：
文献类型：
--
作者：
Gleeson, H. F.;Southern, C. D.;Gortz, V.
用光学方法研究液晶的取向有序性既方便又有效。一些最早的方法利用折射率各向异性的测量，遵循Halle [1]的方法来测量序参量，[图像省略]。简要回顾了这种方法，并介绍了一些典型的应用领域。拉曼光谱是本文讨论的第二种方法。虽然从技术上讲是一种更复杂的方法，但拉曼光谱具有显著的优势，除了能够测量[图像省略]之外，还可以确定[图像省略]。目前的方法进行审查。最近，已经表明偏振拉曼光谱可以用来确定液晶中的双轴序参数。描述的方法，和数据，提出了这样的测量一系列的芯的双晶材料，可以表现出难以捉摸的双轴双晶相。
The use of optical methods to study the orientational order in nematic liquid crystals is both convenient and powerful. Some of the earliest approaches made use of measurements of the refractive index anisotropy, following the methodology of Halle [1] to measure the order parameter, [image omitted]. This method is reviewed briefly and some typical areas of application are presented. Raman spectroscopy is a second approach discussed in this paper. Although technically a more complex methodology, Raman spectroscopy has the significant advantage that in addition to being able to measure [image omitted] it is also possible to determine [image omitted]. A review of current approaches is presented. Very recently, it has been shown that polarised Raman spectroscopy can be employed to determine biaxial order parameters in liquid crystals. The methodology is described, and data are presented for such measurements on a series of bent-core nematic materials that could exhibit the elusive biaxial nematic phase.