Abstract
The use of ultra-high vacuum (UHV) technology has been widely accepted as a necessary prerequisite for reproducible data in the field of surface physics and chemistry. Here we review some characteristic fundamental results of thermal desorption, work function and electron diffraction measurements obtained with hydrogen and carbon monoxide interacting with selected transition metal single crystal surfaces (Ni, Ru, Rh and Pd). It will be shown that both the equilibrium adsorbate and substrate structure as well as the kinetics of adsorption and desorption is sensitively influenced by coadsorption phenomena. Coadsorption can easily occur with residual gas atmospheres containing water vapor, carbon monoxide, or hydrocarbons, and leads, in the simplest case, to site blocking effects. Quite often, ligand effects are observed resulting in a pronounced decrease of the heat of adsorption and a reduction of the initial sticking probability.
