ENERGY SHIFTS OF A CU(111) SURFACE BAND UPON ADSORPTION OF CESIUM AND OXYGEN

Angle resolved photoelectron energy spectra show that a Cu(111) surface band shifts rigidly to lower energy upon cesium adsorption and to higher energy upon exposure of a Cs covered Cu(111) surface to oxygen. For Cu(111)/Cs the energy shift at low coverage corresponds to a transfer of 0.5 electrons per adsorbed Cs atom to the surface state. We associate the shift upon oxygen exposure with the formation on the Cu(111) surface of cesiumoxide molecules which are interacting weakly with the substrate. © 1979.