Dresden 2009 – scientific programme
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O: Fachverband Oberflächenphysik
O 46: Time-resolved spectroscopies I
O 46.6: Talk
Thursday, March 26, 2009, 11:45–12:00, SCH A315
Fano line profiles in two-photon photoemission of image-potential states on Si(100) — •Christian Eickhoff1,2, Jens Kopprasch1,2, Cornelius Gahl1, and Martin Weinelt1,2 — 1Max-Born-Institut, Max-Born-Straße 2a, 12489 Berlin, Germany — 2Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
We have studied the surface states on Si(100) by time-, energy- and angle-resolved two-photon photoemission spectroscopy. Tuning the photon energy of the pump pulse between 4.5 and 5.4 eV allows us to populate unoccupied states up to the Si(100) vacuum level. Besides the occupied dangling-bond state Dup, we have identified the Rydberg-like series of image-potential states. Lifetimes and binding-energies of n=1, 2 and 3 will be presented. Significant variation of both the 2PPE peak positions and intensities were found when tuning the photon energy across the Dup to n = 1 and Dup to n = 2 transitions. Below resonance we observe the Dup initial state with the kinetic energy following the pump pulse photon energy. Above resonance the Dup intensity is significantly reduced and the peak position reflects the respective image-potential-state resonances. Around the resonance the lowering in energy of the expected peak position and the intensity variations can be explained by a Fano-like resonance, caused by interference between transitions from Dup to the discrete image-potential-state resonances and the bulk continuum in combination with the finite bandwidth of the laser pulses.