Retardation and many-body effects in multilayer-film adsorption

A discussion is presented of the relation between the film thickness d and the coexisting vapor pressure P for a physisorbed film. The theory of Dzyaloshinskii, Lifshitz, and Pitaevskii (DLP) is used to calculate the chemical potential a-(d)d-3 relative to the value for bulk liquid. The relation is established between the DLP theory and a many-body expansion, of which the Frenkel-Halsey-Hill (FHH) theory is a first approximation to the nonretarded limit. Numerical calculations are performed for the cases of He4, Ne, H2, N2, Ar, O2, CH4, Kr, and Xe films on glass, gold, graphite, Si, quartz, and Al. Typically, the effect of retardation is to reduce the thickness by 20% for d200 AIS. The function (d) is shown to have a universal retardation behavior with a thickness scale (d1/2) depending on both adsorbate and substrate characteristic frequencies.