Date of Original Version
Thin overlayers of Na, K, Rb, and Cs on different sp-metal substrates have been investigated using photoelectron spectroscopy. The alkali core levels show clearly resolved binding-energy shifts between the surface layer, the intermediate layer(s), and the interface layer. The magnitude of these shifts depends on sp metal and on alkali metal. The layer-resolved core-level binding-energy shifts are well reproduced by models based on a thermodynamical description. For three-layer alkali films the core-level binding energy of the intermediate layer is found to exhibit a small but significant shift between different sp-metal substrates. A simple relationship between the core-level binding-energy shift for the interface layer and the difference in rs value between the sp substrate and the adsorbate is shown to exist.
E. Lundgren, R. Nyholm, M. Qvarford, J. N. Andersen, D. Heskett, and S. V. Christensen. (1997). "Unified behavior of alkali core-level binding-energy shifts induced by sp metals." Physical Review B, 56(19), 12560. Available at: http://dx.doi.org/10.1103/PhysRevB.56.12560