Regensburg 2004 – scientific programme

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O: Oberflächenphysik

O 37: Zeitaufgelöste Spektroskopie I

O 37.1: Talk

Thursday, March 11, 2004, 15:45–16:00, H36

Electron-phonon coupling for surface states on Pd(111) — •Andrea Melzer, Martin Weinelt, and Thomas Fauster — Lehrstuhl für Festkörperphysik, Staudtstraße 7, D-91058 Erlangen

Electrons in surface states can be scattered by phonons to bulk states or to states within the surface band at different parallel momentum. The first process usually requires phonons with large momentum compared to the second process. On the Pd(111) surface an unoccupied sp-like surface state exists and can be studied by time-resolved two-photon photoemission. Scattering to bulk states reduces the population in contrast to scattering within the surface band. The first process shows up in a reduced lifetime while both processes increase the linewidth. We have measured the change of lifetime and linewidth for the surface state on Pd(111) for variable temperatures up to 900 K. For the electron-phonon mass enhancement parameter a value of 0.36 is found which is significantly larger than for the occupied surface states on other fcc(111) surfaces. The time-resolved data indicate large contributions from intraband scattering in contrast to theoretical expectations.