Nonwetting and sticking of the heavy rare gases on potassium surfaces

We have investigated the adsorption, growth, and desorption of Ar, Kr, and Xe on K mono- and multilayers on Ru(001) at 6.5 K. In all cases, three-dimensional growth from very low rare gas (RG) coverages on, clearly indicates nonwetting, and the desorption energies for low RG coverages are much lower than the RG sublimation energies, and lower on K multi- than on K monolayers. Nevertheless, initial sticking coefficients of the RG on both types of K layers are well defined and not dominated by nucleation or by impurities or defects. Their values and dependence on type of substrate can be understood qualitatively, and quantitatively for Ar in terms of a recently developed quantum mechanical model, extending adsorption dynamics studies to nonwetting systems.