In a laboratory framework, the cross-section I ( i, s) (α, θ, φ; K 1 / K 3 , K 2 / K 3 , 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, K 1 , K 2 and K 3 , 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, i and 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, I 1 and I 2 , which are due to mode 1 and mode 2 director fluctuations, respectively. Several geometries have been found where either I 1 or I 2 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.
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Akiyama et al. (1980) studied this question.