A molecular beam study of the interaction of CO with clean and hydrogen covered Ru(0001)

The adsorption for CO on clean and hydrogen covered Ru(0001) has been studied with molecular beams. Sticking coefficient measurements provide proof for direct non-activated adsorption with parallel momentum playing an important role in the sticking process. While preadsorbed hydrogen has a site blocking effect for CO adsorption with no displacement being observed at low temperature (140 K), hydrogen can easily be exchanged by CO at higher temperature. While displacing hydrogen at 273 K, a maximum total coverage of CO and H is conserved Helium reflectivity measurements taken while displacing hydrogen indicate the segregation of carbon monoxide and hydrogen into islands already at very low coverages (0.01ML).