Low-temperature adsorption of CO on Cu(111) studied by reflection absorption infrared spectroscopy

The CO/Cu(111) system was studied between 25 and 150 K using reflection absorption infrared spectroscopy (RAIRS). 25 K adsorption results in population of terminal sites. Further CO adsorption simultaneously produced chemisorbed, bridged-CO and physisorption above the chemisorbed layer. Desorption of physisorbed CO triggered formation of a different chemisorbed structure. In terminal-site only ad-layers of 10%:90% 12CO/13CO, the behaviour depended on adsorption temperature. An ordered structure with strong intermolecular interactions was produced following 25 K deposition and heating to 85 K. This remained stable on cooling; heating to 125 K destroyed the structure. Desorption occurred at 150 K. Identical ad-layers, adsorbed at 80 K, showed no evidence of the structure.