UPS measurements of CO chemisorbed and condensed on Rh (111) using synchrotron radiation

Abstract
The photoemission data of the clean Rh(111) surface are strongly dependent upon photon energy in the range 15 to 27.5 eV. Three different chemisorption levels are distinguished for CO chemisorbed on Rh(111) by exploiting the dependence of photoionization cross sections upon photon energy. Exciton–electron and electron–electron scattering dominate the intensity variations of the spectra of CO condensed on Rh(111). The origin of the observed energy level shifts of CO in the three different phases, gas, condensed and chemisorbed, are discussed in terms of relaxation, bonding, and chemical shifts.