IRAS studies of the orientation of acetone molecules in monolayer and multilayer films on Au(1 1 1) surfaces

We have investigated the interaction of acetone with a Au(1 1 1) surface by use of temperature programmed desorption (TPD) and infrared reflection–absorption spectroscopy (IRAS). We find that acetone reversibly adsorbs on Au(1 1 1), with thermal desorption peaks at 160, 137 and 132 K corresponding to acetone desorption from the monolayer, second layer and multilayer, respectively. IRAS data is used to establish that chemisorbed acetone molecules bind to the Au(1 1 1) surface through the oxygen atom in a η1-(O) configuration with the molecular plane tilted with respect to the surface plane to give C1 symmetry at submonolayer and monolayer coverage. In multilayer films, acetone molecules adopt a highly ordered orientation with the molecular plane perpendicular to the metal surface and the CO bond nearly parallel to the surface plane to give Cs symmetry.