Structural study of alkali/simple metal adsorption: Rb and Na on Al(111)

A quantitative structural study of Na and Rb adsorption on Al(111) using normal incidence standing x-ray wave-field triangulation shows that Rb occupies atop adsorption sites and both systems show a constant adsorbate-substrate bond length over the alkali coverage range 0.12--0.33 monolayer. These results indicate that there is directional local bonding in this simple alkali s-p band metal adsorption system, and show that there is no ionic-covalent bonding transition in this coverage range for either system.