The surface energy and entropy of liquid Ga–Bi and Ga–Pb alloys have been studied by means of surface light scattering measurements at various compositions and temperatures between the respective eutectic and monotectic points. Analysis of these results using the Gibbs adsorption equation gives evidence for wetting and prewetting transitions in these alloys completely consistent with a tetra-point wetting scenario (Dietrich S and Schick M 1997 Surf. Sci. 382 178). Surface freezing transitions are observed for conditions near the liquidus curves. In view of their viscoelastic properties and their relation with the wetting film characteristics, we suggest a simple explanation for the observed surface freezing phenomena in terms of nucleation of strongly undercooled wetting films.

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The liquid/vapor interface of imidazolium based ionic liquids, [C6mim][PF6] and [C6mim][BTI], has been probed by capillary wave spectroscopy at various temperatures up to 400K. Separately, the corresponding surface tensions have been measured by the maximum bubble pressure method. Interpretation of the capillary wave spectra with a modified dispersion relation yields the surface dipole moment density γ(T) as a function of temperature. In both systems γ(T) exhibits a characteristic decrease with temperature which indicates an interfacial order–disorder transition. Within the mean field approximation, fits of γ(T) yield the following critical temperatures for this transition: T c = 364K for [C6mim][BTI], and T c = 383K for [C6mim][PF6].