Lifetimes of image-potential states on Cu(100) and Ag(100) measured by femtosecond time-resolved two-photon photoemission

We report time-resolved studies of image-potential states on Cu~100! and Ag~100!. Femtosecond ultravioletpump and infrared-probe techniques combined with two-photon photoemission have been used to measure relaxation dynamics of n51, 2, and 3 image-potential states. We found the lifetimes of these states on Cu~100! at room temperature to be 4066, 120615, and 300620 fs, respectively. The corresponding values for Ag~100! are 5565, 160610, and 360615 fs. @S0163-1829~98!06643-0#