Correlation between work function changes and core-level shifts in alkali overlayers

The authors have measured the work function changes and Na 2p core-level shifts for the systems Na/Cu(111), Na/Ni(111), and Na/Cu(110) as a function of alkali coverage. They find that the coverage dependence of the core-level shift in the first layer is well correlated with the work function change. They suggest that these quantities are related through the coverage dependence of the alkali dipole moment and the position of the centroid of the alkali valence charge density. In order to confirm this relationship, the authors use a simple fitting procedure which is able to reproduce the work function changes from the core-level shifts for all three systems.