X-Ray Scattering Study of the \(Smectic-A_1\) to \(Smectic-A_2\) Transition

Abstract

X-ray scattering measurements are reported for critical \(smectic-A_2\) fluctuations along a line of second-order transitions between the \(smectic-A_1\) and \(smectic-A_2\) phases in mixtures of hexylphenyl cyanobenzoyloxy benzoate \((DB_6)\) and terephthal-bis-butylaniline (TBBA). The measured exponents \(\gamma = 1.46 \pm 0.05\) and \(\nu_{\parallel} = \nu_{\perp}= 0.74 \pm 0.03\) are constant along the second-order line and agree with recent heat-capacity measurements and the scaling law, \(3\nu + \alpha =2\). They disagree with current theoretical expectations.