Critical behavior at the nematic–to–smectic-A transition in a nonpolar liquid crystal with wide nematic range

High-resolution x-ray scattering experiments to study the critical smectic-A fluctuations in the nematic phase have been performed on a mixture of two nonpolar, two-benzene-ring compounds. The ratio ${\mathit{T}}_{\mathit{N}\mathit{A}}$/${\mathit{T}}_{\mathit{N}\mathit{I}}$ (=0.885) for this mixture is much smaller than for previously studied similar materials. The smectic correlation lengths parallel and perpendicular to the smectic-layer normal are found to diverge anisotropically with characteristic exponents ${\nu }_{\mathrm{?}}$=0.75±0.03, ${\nu }_{\mathrm{\perp }}$=0.65±0.03, and the susceptibility with γ=1.24±0.05.