CO Blocking of D-2 Dissociative Adsorption on Ru(0001)

The influence of pre-adsorbed CO on the dissociative adsorption of D-2 on Ru(0001) is studied by molecular-beam techniques. We determine the initial dissociation probability of D-2 as a function of its kinetic energy for various CO pre-coverages between 0.00 and 0.67 monolayers (ML) at a surface temperature of 780 K The results indicate that CO blocks D-2 dissociation and perturbs the local surface reactivity up to the nearest-neighbour Ru atoms. Non-activated sticking and dissociation become less important with increasing CO coverage, and vanish at theta(CO) approximate to 0.33 ML. In addition, at high D-2 kinetic energy (> 35 kJ mol(-1)) the site-blocking capability of CO decreases rapidly. These observations are attributed to a CO-induced activation barrier for D-2 dissociation in the vicinity of CO molecules.