Light scattering near the nematic–smectic-Aliquid-crystal phase transition

We report the results of light scattering on liquid-crystal materials near the nematic–smectic-A phase transition. Measurements were made both in the nematic and smectic-A phases. The critical exponents for the twist elastic coefficient ($K_2$) and the layer dilation elastic coefficient (B¯) were measured and appear to scale, within experimental uncertainty, as predicted by the de Gennes model. The exponents for these relatively wider nematic range materials are somewhat larger than those found in most previous light scattering studies, indicating somewhat better agreement with the theoretically predicted values for the isotropic 3D XY model, though still considerably smaller.