Smectic layering at the free surface of liquid crystals in the nematic phase: X-ray reflectivity.
Smectic layering at the free surface of liquid crystals in the nematic phase: X-ray reflectivity.
复制标题
向列相液晶自由表面的近晶分层：X 射线反射率。
DOI：
10.1103/physreva.35.4800
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
J. Als
中科院分区：
文献类型：
--
作者：
P. Pershan;A. Braslau;A. Weiss;J. Als
近晶分层的表面和近晶的波动，可以同时研究X射线镜面反射率和散射测量。有一个峰值的角度依赖性的镜面反射率由于表面诱导的近晶分层，穿透到散装的exp（-z/λ？）在哪里？是一个临界相关长度。通过对液晶材料辛氧基氰基联苯（8 OCB）和丁氧基亚苄基辛基苯胺（4 O）的测量说明了这一点。8）。在这两种情况下，在镜面反射率的峰值强度的临界发散弱于？2，暗示意想不到的表面物理学。密度对相关函数的临界部分的绝对值通过与菲涅耳反射强度的比较来确定。不同的几何形状的X射线光谱仪进行了讨论。
Smectic layering at the surface and smectic fluctuations in the bulk can be studied simultaneously by x-ray specular reflectivity and scattering measurements. There is a peak in the angular dependence of the specular reflectivity due to surface-induced smectic layering that penetrates into the bulk as exp (-z/ξ?) where ξ? is one of the nematic critical correlation lengths. This is illustrated by measurements of the liquid-crystal materials octyloxycyanobiphenyl (8OCB) and butyloxybenzyl-idene octylaniline (4O. 8). In both cases the critical divergence of the intensity of the peak in the specular reflectivity is weaker than ξ? 2, suggesting unexpected surface physics. The absolute value of the critical part of the density pair correlation function is determined by comparison to the Fresnel reflected intensity. Different geometries of the x-ray spectrometer are also discussed.