Regensburg 1998 – scientific programme
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O: Oberflächenphysik
O 38: Elektronische Struktur (Experiment und Theorie) (IV)
O 38.1: Talk
Friday, March 27, 1998, 11:15–11:30, H37
Effects of laser linewidth in fs time-resolved spectroscopy of image-potential states — •I. L. Shumay1, Ch. Reuß1, U. Thomann1, M. Weinelt1, U. Höfer2, and Th. Fauster1 — 1Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen — 2Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85740 Garching
Recent breakthrough [1,2] in precise lifetime measurements of image-potential states on a number of clean metal surfaces by femtosecond time-resolved two-photon photoelectron spectroscopy has drawn attention to different relaxation mechanisms of photoexcited electrons. It has been shown that time-resolved experiments allow one to measure the energy relaxation time T1. On the other hand, the intrinsic linewidth from energy-resolved spectra is equal to Γ=1/2T1+1/T2*, where T2* is the dephasing time. However, a broad spectral width of both pump and probe pulses in fs experiments may have a dramatic effect on the deduced lifetimes. We present our energy- and time-resolved measurements on Cu(100) and Cu(111) surfaces showing an interplay between on- and off-resonance excitation. The results are discussed within the framework of optical Bloch equations with proper account for off-resonant excitation.
[1] T. Hertel, E. Knoesel, M. Wolf, and G. Ertl, Phys. Rev. Lett. 76, 535 (1996).
[2] U. Höfer, I. L. Shumay, Ch. Reuß, U. Thomann, W. Wallauer, Th. Fauster, Science 277, 1480 (1997).