Long-Range Forces between Molecules and Metals

Isotherms of oxygen, argon, neopentane, tetramethylsilane, and diethyl ether on optically flat gold surfaces have been determined over the range 0-70 Brunauer-Emmett-Teller) (BET) monolayers, corresponding to 0-220 {}. The results are found to imply a potential energy of interaction $U(Z)$ of the form U(Z)=α1.74×10^-4Z^-2 erg/molecule, where α is the molecular polarizability and Z the distance from the surface. The possible source of the disagreement between the experimental results and the theoretical predictions of Margenau, Bardeen, and Lennard-Jones is briefly discussed.