Absolute Measurement of the Critical Properties of Second Sound at the Smectic-A-to-Nematic Phase Transition in 8OCB

Abstract

Light scattered from the driven free surface of the smectic-A phase of octyloxy cyanobiphenyl (8OCB) provides a low-frequency measurement of second sound. This yields an absolute measurement of the smectic elastic constant, B. There is no dispersion in either the angular or frequency dependence of B for angles \(35^{\circ}-83^{\circ}\) from the normal and for frequencies from 10-100 kHz. Near the smectic-A-to-nematic phase transition the smectic elastic constant can be described by \(B=(6.03 \pm 0.05) \times 10^7 (T_{NA}-T)^{0.32 \pm 0.015} dyn/cm^2\).