Experimental observation of hysteresis in a wetting transition

An ellipsometric study of the cyclohexane-methanol mixture shows that in the wetting regime, either a very thin or a thick film is formed at the liquid/vapor interface. The observed hysteresis is consistent with the assumption that the wetting transition is first order. The thick layer can be accounted for by the stabilization of the wetting layer by long-range van der Waals forces. In agreement with this, the equilibrium wetting layer thickness shows no dependence on the temperature. The thin film is shown to be governed by short-range forces.