Time-resolved photoemission from image-potential states

Electrons attracted by the image force to a metal surface are loosely bound and form a Rydberg-like series of states converging towards the vacuum lev el. Energies and lineshapes of these image-potential states are studied by two-photon photoelectron spectroscopy. The use of Ti-sapphire lasers as lig ht sources has raised the count rates by several orders of magnitude and pr ovided the opportunity to study the lifetime in the femtosecond range. Cohe rent excitation of several higher image-potential states of the Rydberg-lik e series leads to the observation of quantum beats in the time domain. The decay of the beat pattern and the lifetime are strongly influenced by adsor bates. The dependence on the quantum number of the image-potential states a nd the adsorbate will be discussed. The model system of image-potential sta tes can be studied extremely well in present experiments and the results co ntribute to the understanding of photochemical processes and hot-electron d ynamics at surfaces. (C) 2001 Elsevier Science B.V. All rights reserved.