Shortminus;range order fluctuations in the isotropic phase of a liquid crystal MBBA

摘要

We have measured the polarized (Ipar;) and the depolarized (Iperp;) scattered light intensities by fluctuations of the orientational order parameter as a function of two scattering angles over a range of temperatures close to and above the isotropicminus;nematic phase transition ofparaminus;methoxybenzylidineparaminus;nminus;butylaniline (MBBA). The coherence length khgr; was found to diverge as egr;minus;0.50plusmn;0.01, in essential agreement with the last results of Stinson and Litster and the theoretical predictions of de Gennes, where egr; = (Tminus;Tcast;)/Tcast; andTcast; is a pseudocritical temperature slightly belowTp. We have also measured the temperature dependence of the extinction coefficient of MBBA using the 632.8 nm wavelength of Heminus;Ne laser light and observed that (limKmgr;0) 1/Ipar;orperp;after attenuation correction diverges as egr;ggr;with ggr; = 0.85plusmn;0.05 which differs from ggr; = 1 as reported by previous studies.Krepresents the magnitude of the momentum transfer vector.