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O: Oberflächenphysik

O 50: Time-resolved spectroscopy II

O 50.5: Vortrag

Freitag, 31. März 2006, 12:15–12:30, WIL C207

Transition of Ar/Cu image-potential states from short-lived scattering resonances to long-lived quasi-bound interface states — •M. Rohleder, W. Berthold, J. Güdde, and U. Höfer — Fachbereich Physik, Philipps-Universität, D-35032

In the presence of thick Ar overlayers the image potential of Cu(100) gives rise to interface electronic states above the vacuum level. In previous experiments [1,2] we have shown that fundamental aspects of the dynamics of electronic decay at buried solid-solid interfaces and fast electron transfer processes through thin insulators can be investigated for this system by means of time-resolved two-photon photoemission (2PPE). Here, we demonstrate that these interface states may also be observed as final-state resonances in conventional one-photon photoemission (1PPE). Spectroscopically, this has advantages in terms of a higher accessible energy range above the vacuum level. With increasing layer thickness the hydrogen-like series shows a transition from broad resonances in the Ar conduction band into more narrow quasi-bound states confined to the Ar/Cu interface. We compare the experimental results with theoretical resonance positions and linewidths derived from a parametrized one-dimensional potential. For electrons with small momenta perpendicular to the surface we find excellent agreement between calculated and measured energies. The calculated widths of the lowest lying resonances agree well with the electron transfers times measured by 2PPE whereas the 1PPE spectra are apparently broadened by other contributions.

[1] M. Rohleder et al., Phys. Rev. Lett. 94, 017401 (2005).

[2] M. Rohleder et al., New. J. Phys. 7, 103 (2005).