Measurements of intrinsic linewidth versus parallel momentum of image-potential states on Ag(1 0 0)

Intrinsic linewidths of electronic image-potential states versus the momentum parallel to the surface on Ag(1 0 0) have been measured with angle resolved two-photon photoemission using the time of flight technique. The influence of the time of flight spectrometer angular acceptance on intrinsic linewidth measurements is taken into account and a proper data analysis is proposed. The inverse linewidth as a function of parallel momentum is compared with time-resolved measurements of image-state lifetimes on Ag(1 0 0) and Cu(1 0 0) reported in the literature. The data analysis shows that decay dynamics of image potential states in Ag and Cu may be determined by different physical mechanisms.