Electron-stimulated desorption study of oxygen adsorbed on Ag(110). Observation of inclined physisorbed species

Physisorbed molecular oxygen adsorbed on the Ag(110) surface was studied by temperature-programmed desorption (TPD) and time-of-flight electron-stimulated desorption ion angular distribution (TOF-ESDIAD). Oxygen molecules in the first physisorbed layer are tilted strongly from the surface normal and are oriented parallel to either the or the azimuthal crystallographic directions of the Ag(110) surface, based on measurements of the trajectory of O+ ions produced by electron impact. In the multilayer regime, oxygen molecules are mainly aligned parallel to the azimuth with an O−O bond direction close to the surface normal. ESD cross sections for both O+ ion formation and for O2 desorption have been measured for the physisorbed species.