The orientational order parameters $⟨P_2⟩$ and $⟨P_4⟩$ in the nematic liquid crystal 4-pentyl-4'-cyanobipheny (5CB) have been determined by means of the two completely different techniques: polarized Raman spectroscopy and x-ray scattering. In particular, the values of $⟨P_2⟩$ and $⟨P_4⟩$ obtained using two different Raman methods, proposed by Jen et al. [J. Chem. Phys 66, 4635 (1977)] and Jones et al. [J. Mol. Struct. 708, 145 (2004)], respectively, are compared with the results of x-ray measurements. A good agreement between the experimental values of $⟨P_2⟩$ and $⟨P_4⟩$ and the results of the Humphries-James-Luckhurst mean field theory has been found whenever they were determined using either x-ray measurement or following the Jen et al. method. In addition, a study of the influence of the intensity of the exiting laser source on the apparent values of the order parameters has been performed. Therefore, it was found that the discrepancies of the value of $⟨P_4⟩$ determined following Jen et al. and Jones et al. could be determined by nonlinear effects.

• Received 30 June 2009

DOI:https://doi.org/10.1103/PhysRevE.81.021707