Theoretical Study of the Monolayer Adsorption of Argon on a Xenon Surface

A theoretical analysis is given of a portion of the experimental data of Prenzlow and Halsey on the adsorption of argon on a preadsorbed xenon layer. The potential-energy functions for Ar atoms over a square-packed and a triangular-packed xenon layer on a graphitic substrate are computed, and it is argued that the argon atoms should be highly localized at the experimental temperatures in such a potential field. Consequently, the data are compared with theoretical lattice-gas thermodynamic properties for a square and a triangular lattice and it is shown that better agreement between experiment and theory is found if a square-packed lattice is assumed. The validity of this conclusion and its physical implications are discussed.