Regensburg 2004 – wissenschaftliches Programm
O 45.1: Vortrag
Freitag, 12. März 2004, 11:15–11:30, H39
Two-pulse correlation of femtosecond laser-induced diffusion of oxygen on Pt(111) — •K. Stépán, J. Güdde, and U. Höfer — Fachbereich Physik, Philipps-Universität Marburg, D-35032 Marburg
We have studied the mechanism of oxygen diffusion on Pt(111) induced by femtosecond laser pulses. The dissociative adsorption of O2 on a vicinal surface was used to selectively decorate the step sites with atomic oxygen . Diffusion from the step edges onto the terraces was induced at a substrate temperature of T=80 K by 100-fs, 800-nm pump pulses with absorbed fluences of 8-16 mJ/cm2. It was monitored in situ with optical second-harmonic generation (SHG) by exploiting the sensitivity of SHG to surface symmetry. The diffusion mechanism was explored in the time domain by performing measurements of the diffusion efficiency as a function of the delay time between two cross-polarized pump pulses. The two-pulse correlation has a width of about 1 ps. This indicates a diffusion process induced by multiple excitations from the hot electron gas of the metal, similar to the meanwhile well-studied phenomenon of desorption induced by multiple electronic excitations (DIMET) .
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