Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 5: Electron and spin dynamics I

O 5.2: Talk

Monday, March 22, 2010, 11:30–11:45, H34

Image-Potential Resonances on Al(100) — •Matthias Schult, Manuel Marks, Jens Güdde, and Ulrich Höfer — Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany

The Hydrogen-like image-potential (IP) states provide a well understood model system to study electron dynamics at metal surfaces. The energy of these states is usually located within the projected bulk band gap, which limits the penetration of the excited electrons into the bulk. In many surface phenomena that are connected to electron transfer, however, electronic resonances, i.e. electronic states at the surface that are resonant with bulk states, play an important role.

At Al(100) the vacuum energy lies 6 eV above the projected bulk band gap and the whole series of IP states form surface resonances with strong coupling to bulk states. Excited electrons in these resonances can not only decay by electron-hole pair excitation, but can also scatter elastically into the bulk. Therefore, much shorter lifetimes and broader linewidths compared to noble metal surfaces can be expected.

In this talk we present experimental results on the energies and lifetimes of IP resonances on the Al(100) surface obtained by time-resolved two-photon photoemission. In the photoelectron spectra the first members of the IP resonance series up to n=3 could be resolved. For n≥ 3 lifetimes that are longer than the experimental time-resolution of 60 fs could be observed. We will compare the experimental results to calculations using a one-dimensional model potential, which predict binding energies and the elastic contribution to the lifetimes.