Time-dependent electron phenomena at surfaces.

Femtosecond and subfemtosecond time scales typically rule elec- tron dynamics at metal surfaces. Recent advance in experimental techniques permits now remarkable precision in the description of these processes. In particular, shorter time scales, smaller system sizes, and spin-dependent effects are current targets of interest. In this article, we use state-of-the-art theoretical methods to analyze these refined features of electron dynamics. We show that the screening of localized charges at metal surfaces is created locally in the attoseconci time scale, while collective excitations transfer the perturbation to larger distances in longer time scales. We pre- dict that the elastic width of the resonance in excited alkali adsor- bates on ferromagnetic surfaces can d~pend on spin orientation in a counterintuitive way. Finally, we quantitatively evaluate the elec- tron-electron and electron-phonon contributions to the electronic excited states widths in ultrathin metal layers. We conclude that confinement and spin effects are key factors in the behavior of electron dynamics at metal surfaces. [ABSTRACT FROM AUTHOR]