ELECTRON MEAN FREE-PATH IN BE METAL

Photoemission data in which the signals from the first two atomic layers are well distinguished from that of the bulk are used to determine the kinetic-energy dependence of the inelastic electron mean free path in Be metal. Using a layer attenuation model, the electron mean free path is extracted from experimental core-level data recorded from the Be(0001) and Be(101̄0) surfaces. The values determined for the two surfaces show a good overall agreement and the mean free path is found to exhibit a pronounced minimum at an electron kinetic energy of around 25 eV. The experimental results are compared with the mean free path calculated using the approach originally applied by Quinn. The experimental and calculated values are found to agree fairly well at higher energies. At lower energies the experimental values drop significantly below the theoretical values and locate the minimum at a markedly smaller kinetic energy. Possible reasons for this discrepancy are discussed. © 1994 The American Physical Society.