TEMPORAL AND LOCAL REDUCTION OF A POTENTIAL-ENERGY WELL UNDER DYNAMIC EQUILIBRIUM - CO ON NI(100)

Direct observation of dynamic equilibrium between preadsorbed (CO)C-13-O-18 and gas phase (CO)C-12-O-16 by means of time-resolved infrared reflection absorption spectroscopy at several temperatures from 350 to 400 K reveals that the desorption process under gas phase CO is enhanced due to the repulsive interaction between preadsorbed (CO)C-13-O-18 and incident (CO)C-12-O-16 molecules from the gas phase arriving at nearby sites of adsorbed CO. As a result, the activation energy is reduced from 127 kJ mol-1, the value for desorption into vacuum, to 25 kJ mol-1 even for theta = 0.1-0.3 monolayer (ML) and a CO flux of 0.001 ML s-1.