COVERAGE-DEPENDENT CORE-LEVEL BINDING-ENERGY SHIFTS OF ALKALI-METAL ATOMS ON METAL-SURFACES

Coverage-dependent core-level binding energies of the Na 2p level of Na adsorbed on Cu(111) and Ni(111) surfaces are measured and compared to a first-principles calculation of Na on jellium. Similar behavior of the Na 2p level for both Cu and Ni suggests a substrate-independent core-level shift mechanism. The result of a local-density-functional calculation of the electrostatic potential-energy change as a function of alkali-metal coverage allows us to separate out the contributions of initial- and final-state effects in the coverage dependence of alkali-metal core-level binding-energy shifts.