Surface-state hole decay mechanisms: The Be(0001) surface

First-principle calculations and angle-resolved photoemission experiments are combined to analyze the different contributions to the surface-state hole dynamics at the Be(0001) surface. The computed inelastic electron-electron scattering rate gamma is in good agreement with experiment once the electron-phonon contribution is subtracted. gamma is strongly influenced by details of the surface band structure. In particular, the intraband transitions within the surface state itself ignored in traditional Fermi liquid theory contribute 65%-85% to gamma. This intraband contribution and the highly spatial nonlocality of the self-energy makes the energy and momentum dependence of gamma to be proportional to (E-F-E)(alpha) (with alpha <2) in contrast to the observed similar or equal to2 value in noble and transition metal surfaces.