  Using synchrotron radiation with a photon energy of 15 keV, the molecular
structure of an adsorbed n-triacontanol layer at the n-hexadecane - water
interface in different its phase states has been studied by the method of
diffuse X-ray scattering. The analysis of the experimental data shows that a
transition to the multilayer adsorption occurs at a temperature below the
two-dimensional vapor - liquid transition at the interface. This transition has
been attributed to a feature in the temperature dependence of the concentration
of micelles in a surface layer 100 - 200 {\AA} thick.
