We report here a detailed RAIRS study of carbon monoxide adsorbed on the Cu(1 1 1) surface at substrate temperatures of 15-20 K. Surface diffusion in this temperature regime is thermally limited this results in the formation of a different. more disordered surface structure than those grown at higher temperatures. Both monolayer and multilayer physisorption is observed. and these layers are found to affect the underlying chemisorbed layer. (C) 2002 Published by Elsevier Science B.V.