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Dependence of Rayleigh Line Intensity on Scattering Angle in Aligned Nematie Liquid Crystals

1980; Institute of Physics; Volume: 19; Issue: 10 Linguagem: Inglês

10.1143/jjap.19.1937

1347-4065

Ryuichi Akiyama, Yukihiko SAITO, Atsuo Fukuda, Eiichi Kuze, Nobuyuki Goto,

Spectroscopy and Quantum Chemical Studies

In a laboratory framework, the cross-section I(\hat i,\hat s)(α, θ, φ; K1/K3, K2/K3, n//, n⊥) has been numerically calculated and graphically presented in the (α, φ) space for fixed θ values; θ and φ specify the average director direction and α is the scattering angle. Parameter values used are the Frank elastic constants, K1, K2 and K3, and the indices of refraction, n// and n⊥, for MBBA at 20°C. The cross-section depends on whether the states of polarization of the incident and scattered lights, \hat i and \hat s, are extraordinary (E) or ordinary (O). Among the four cases, I(O,O) is always zero; when α<10°, I(E,E) is about 10 times as strong as I(E,O) and I(O,E). The cross-section consists of two terms, I1 and I2, which are due to mode 1 and mode 2 director fluctuations, respectively. Several geometries have been found where either I1 or I2 is zero or very small compared with the other. The scattering patterns in the (α, φ) space are characterized by several zero lines, which may be used for determining the so-called "tilt angle". To demonstrate this possibility, I(E,E) and I(E,O) at θ=90° have been observed as a function of φ by varying α as a parameter. The temperature variation of the cross-section has also been discussed.