Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 48: Surface dynamics I
O 48.2: Vortrag
Mittwoch, 24. März 2010, 10:45–11:00, H40
Fluence-dependent two-pulse correlation for electronically induced diffusion of O/Pt(111) — •Kristina Klass1, Gerson Mette1, Jens Güdde1, Michael Dürr1,2, and Ulrich Höfer1 — 1Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032 Marburg — 2Fakultät Angewandte Naturwissenschaften, Hochschule Esslingen, D-73728 Esslingen
We present results of a time-domain study of electronically induced diffusion of atomic oxygen on a vicinal Pt(111) surface. At low substrate temperatures, hot electrons are excited by femtosecond laser pulses and result in a hopping of O atoms from the O-saturated steps onto the terraces. Optical second-harmonic generation (SHG) was used to observe this process via monitoring the occupation of the step sites. The strong fluence dependence of the diffusion process was detected via SHG microscopy by analyzing the signal across the laser beam profile. In combination with two-pulse correlation measurements this techniques was used to study the dynamics of energy flow from the initial excited substrate electrons to the adsorbate degree of freedom at different laser fluences. The widths of the two-pulse-correlations are in the picosecond range and increase with increasing laser fluence. The results are qualitatively similar to those obtained recently for CO/Pt(111) [1]. They are discussed on the basis of an empirical friction model using an electronic friction coefficient that depends on excitation density.