Ellipsometric determination of universal critical adsorption scaling functions

In this paper we determine and compare a number of theoretical models which describe the universal scaling functions for critical adsorption in the strong surface field limit. The P1 and P3 models, which are continuous up to and including the first and third derivatives, respectively, provide excellent descriptions of the ellipsometric data for four different critical binary liquid mixtures. The exponential-Pade model, initially proposed by Liu and Fisher [Phys. Rev. A 40, 7202 (1989)], provides a reasonable but less accurate description of the one-phase experimental data. This later model has the advantage, however, that it is continuous in all derivatives.