METASTABLE WETTING LAYERS

In the two-phase region of a critical binary liquid mixture a wetting layer of the heavier phase can occur at the upper liquid-vapor surface sufficiently close to the critical temperature. This wetting layer ca n be either stable or metastable to long-wavelength capillary wave flu ctuations on the adjacent critical interface. The stability depends up on the sip and slope of the dispersion force curve F(d). We classify t he four main generic shapes for F(d), which determines the stability o r metastability of the wetting layer, in terms of the relative magnitu des of the static and visible dielectric constants for the two liquid components. For realistic values of the liquid-mixture parameters we c alculate the critical wavelength beyond which fluctuations are unstabl e and also determine the lifetime of the metastable state. The life-ti me can vary from seconds to many hours.