IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS1-MoP

Paper SS1-MoP4
Femtosecond Dynamics of Electrons in Image-potential States on Stepped Cu(001)

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Electronic Structure Poster Session
Presenter: M. Roth, Universität Erlangen-Nürnberg, Germany
Authors: M. Roth, Universität Erlangen-Nürnberg, Germany
M. Pickel, Universität Erlangen-Nürnberg, Germany
J. Wang, Universität Erlangen-Nürnberg, Germany
M. Weinelt, Universität Erlangen-Nürnberg, Germany
Th. Fauster, Universität Erlangen-Nürnberg, Germany
Correspondent: Click to Email
The Rydberg-like series of image-potential states (|n>, n = 1, 2, ...) is a prototype system for loosely bound electrons at a metal surface. The electronic structure and the femtosecond dynamic of these states is studied by energy- and time-resolved two-photon photoemission spectroscopy. The electron trapped in the image-potential moves virtually free lateral to the surface exhibiting a parabolic dispersion with effective mass close to the free-electron mass. In this intermediate state the electron is subject to inelastic and quasielastic scattering processes which cause decay of the population and phase relaxation. The influence of surface corrugation on these processes has been investigated for stepped Cu(117) and Cu(119) surfaces which are vicinal to Cu(001). The dynamics depend on both the distance of the electron in front of the surface (~ n@super 2@) and the parallel momentum perpendicular to the step edge. Only for the lowest image-potential state |1> we can identify umklapp processes. An electron in this state which moves upstairs apparently has a longer lifetime than an electron moving downstairs. In the second image-potential state |2> the decay rate decreases linearly with kinetic energy but independent of direction. While quasielastic scattering with small momentum transfer is mainly observed for the first image-potential state, the population of state |2> decays in addition via resonant scattering from the band bottom to states of band |1> with finite momentum. Compared to the Cu(001) surface the latter process is considerably enhanced on the stepped surfaces.