Coadsorption of NO + CO and CO + NO on Cu(001) at 115 K was investigated by valence band and core-level photoetectron spectroscopy based on the use of synchrotron radiation (SR-PS). Site exchange between NO and CO takes place when a CO saturated Cu(001) surface is exposed to NO. Both molecular and dissociated NO are observed on the surface. The effect of heating to 300 K was followed. The opposite adsorption sequence, CO exposure of the Cu(001) surface with preadsorbed NO, results in oxidation of CO and bonding Of CO2. Heating to 300 K causes desorption of the adsorbed CO2, NO and N. (c) 2005 Elsevier B.V. All rights reserved.