  Theoretical investigations of surface-state electron dynamics in noble metals
are reported. The dynamically screened interaction is computed, within
many-body theory, by going beyond a free-electron description of the metal
surface. Calculations of the inelastic linewidth of Shockley surface-state
electrons and holes in these materials are also presented. While the linewidth
of excited holes at the surface-state band edge (${\bf k}_\parallel=0$) is
dominated by a two-dimensional decay channel, within the surface-state band
itself, our calculations indicate that major contributions to the
electron-electron interaction of surface-state electrons above the Fermi level
come from the underlying bulk electrons.
