Desorption and molecular interactions on surfaces: CO/Rh(110), CO/Rh(100) and CO/Rh(111)

We present studies of the isothermal desorption of carbon monoxide from the three low index rhodium surfaces using time-resolved electron energy loss spectroscopy (TREELS). We use a quasiequilibrium model and apply lattice gas theory and the transfer matrix technique to model the desorption isotherms. With the further assumption that the nearest neighbor interaction energy between chemisorbed CO molecules is large and repulsive, we extract the second and third neighbor lattice energies for all three surfaces. We compare our results with the ordered CO overlayer structures reported by low electron energy diffraction measurements. We find that the lateral interaction energies on all three surfaces exhibit weak but non-negligible repulsion and attraction. We also examine and discuss the validity of the quasiequilibrium assumption in analyzing desorption measurements. Finally, we compare and discuss the trends in observed CO structures on various transition metal surfaces. (C) 1997 Elsevier Science B.V.