NUCLEATED WETTING LAYERS

We observe a new wetting layer growth mechanism at the liquid/vapor surface of the critical mixture acetone + hexadecane. After spinodal decomposition of the bulk liquid, a metastable surface state forms. This metastable state is consistent with critical adsorption and persists until a wetting film or droplets of the lower phase are nucleated at the surface. Film growth occurs for DELTA-T = T(c) - T < 0.1-degrees-C while droplet growth occurs for DELTA-T > 0.1-degrees-C. The droplet nucleation time is consistent with classical nucleation theory provided the droplet line tension, L, is included in the surface free energy. We determine that L is similar to t0.83 close to T(c) where t is the reduced temperature.