Surface-binding-energy shifts for sodium, magnesium, and aluminum metals

The core-level binding-energy shifts for surface atoms relative to bulk atoms ("surface shifts") have been measured for the $2p$ levels of Na (220 meV) and Mg (140 meV) using synchrotron-radiation-excited photoelectron spectroscopy. For Al, both a surface shift and a broadening are considered. The sign and magnitude of these shifts are compared with calculated values based on surface energies. The mean free path of the photoelectrons is determined by evaluation of the intensity ratio $\frac{I_{\mathrm{bulk}}\mathrm{}\left(2p\right)\mathrm{}}{I_{\mathrm{surface}}\mathrm{}\left(2p\right)\mathrm{}}$.