Capillary-wave relaxation for a meniscus between miscible liquids

We have measured autocorrelation functions for light scattered from capillary waves at the interface in a near-critical binary liquid mixture both at two-phase equilibrium and after abruptly raising the temperature to drive the system toward one-phase equilibrium. Use of the capillary-wave dispersion relation allows the extraction of an effective ``surface tension.'' This surface tension represents a dynamical integrity of the nonequilibrium interface which may affect pattern formation when the interface is driven.