Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 29: Zeitaufgelöste Spektroskopie II

O 29.1: Vortrag

Donnerstag, 27. März 2003, 11:15–11:30, FOE/ORG

Band structure of Ar adlayers probed by two-photon photoemission — •K. Duncker, M. Rohleder, W. Berthold, J. Güdde, and U. Höfer — Fachbereich Physik, Philipps-Universtät, D-35032 Marburg

Using angle-resolved two-photon photoemission (2PPE) we studied the effects of Ar adsorption on the dispersion properties of the unoccupied electronic states of the Cu(100) surface. Although adsorption of 4 monolayers (ML) leads to strong decoupling of the n=1 image-potential state from the bulk metal[1], the effective mass of parallel motion remains unaltered with a value close to unity. As, in this case, the electron stays outside the layer in the vacuum, the interaction with the Ar potential is very weak. Ar layers, on the contrary, with thicknesses larger than 20 ML can sustain a series of image-like resonance states, which are completely localized inside the layer. For the lowest n′=1 state we find an effective mass of only 0.5, which equals the literature value of the effective mass at the Ar conduction band minimum. This can be explained, because the states are derived from the Ar 4s conduction band and thus follow the same dispersion relation.

[1] W. Berthold, P. Feulner, and U. Höfer, Chem. Phys. Lett. 358, 502 (2002).