Interaction of Molecular Oxygen with Au (001) Surface*

Kinetics of dioxygen - Au (001) surface interaction has been studied at high temperature and near atmospheric pressures with in situ x-ray scattering measurements. We find that the hexagonal reconstruction (hex) of Au (001) surface lifts to (1\texttimes 1) in the presence of dioxygen. The measured lifting rate constant vs. temperature shows a `volcano'-type behavior indicating that oxygen adsorption limits at high temperature while activation barrier of the lifting limits at low temperature. The pressure--temperature (PT) phase diagram obtained in our study shows three regions: hex at low P and T, (1\texttimes 1) at high P and T, and coexistence of the hex and the (1\texttimes 1) at the intermediate P and T.