Photoemission from Al(100) and (111): Experiment and ab initio theory

Photoelectron spectra from (100) and (111) surfaces of aluminum in the photon energy range 44\char21{}100 eV are measured and calculated within an ab initio one-step theory. Dispersion of spectral structures is interpreted in terms of unoccupied electronic structure of a semi-infinite crystal. The energy dependence of complex self-energy is derived from the experiment. The lifetimes of the (100) and (111) surface states and the photon energy dependence of the intensity of photoemission from the surface states are determined. A broad spectral structure is experimentally observed at the (111) surface, which disappears at the room temperature. It is tentatively interpreted as a surface resonance.