Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)

O 29.52: Poster

Wednesday, March 29, 2006, 14:30–17:30, P2

Chirped-Pulse Two Photon Photoemission spectroscopy from surfaces — •Felix Steeb, Stefan Mathias, Michael Bauer, and Martin Aeschlimann — FB Physik, TU Kaiserslautern, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern

Two-Photon Photoemission (2PPE) with ultrashort laser pulses is a well-established technique which has been successfully applied to the investigation of the structure and dynamics of electron excitations at surfaces. In this paper, we show that the spectral chirp of the exciting laser pulse is an additional experimental parameter which can be utilised to gather further information on the electron states involved in the 2PPE process.

A well-defined amount of spectral chirp is applied to the ultrashort laser pulse. For a series of differently chirped pulses, the appropriate 2PPE spectra were recorded. In the case of a clean and a cesium covered Cu(111) surface, we observe significant energy shifts as large as 40 meV from the occupied shockley surface state and from the unoccupied cesium resonance respectively.

Model calculations within the framework of the Liouville-von-Neumann equations reproduce the experimental results for the photoexcited adsorbate and enable us to relate this shift to the finite lifetime of the adsorbate resonance. On the other hand, a lack of any energy shift of the shockley surface state in the simulations point to a need for further development of the theoretical model. The results and future prospects, e.g. the interaction of spectral chirp and adsorbate motion are discussed.