Effects of vibrational and rotational excitations on the dissociative adsorption of O2 on Cu surfaces

We report an X-ray photoemission study of the dissociative adsorption of O-2 on Cu(111), (001), and (110) surfaces with an O-2 molecular beam generated with a variable temperature nozzle. The O-uptake curves, which are produced from precisely measured O-1s peaks, indicate that the dissociative absorption is enhanced as the nozzle temperature is increased up to similar to 1000 K for the normal incidence of O-2 at a kinetic energy of 0.5 eV. However, further increasing the nozzle temperature T-n to 1400 K reduces the probability of dissociative adsorption. These results suggest that vibrational excitations of incident O-2 assist dissociative adsorption while rotational excitations hinder it.