Properties of the adsorption layer in a binary liquid mixture near the critical point

A method for the determination of parameters of the surface layer (thickness and refraction index) at the liquid-vapor interface in binary liquid mixtures was developed. The parameters of the surface layer for the C$_7$H$_{14}$-C$_7$F$_{14}$ liquid mixture in the vicinity of the critical point, which was studied by means of ellipsometry in [1], were calculated using the proposed method. The temperature dependences of the thickness and refraction index that were determined in the homogeneous isotropic layer approximation at the interface liquid-vapor, show structural peculiarities that were not observed earlier. Their appearance is explained by the possible influence of hydrodynamic processes at the boundary.