Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 68: Focussed session: Functional molecules at surfaces III
O 68.6: Vortrag
Donnerstag, 29. März 2012, 12:30–12:45, A 053
Electron Dynamics in Azobenzene SAMs on Gold — •Stefanie Paarmann, Cornelius Gahl, and Weinelt Martin — Fachbereich Physik, Arnimallee 14, 14195 Berlin
Electronic structure and femtosecond electron dynamics of self-assembled monolayers of azobenzene functionalized alkanethiols on gold have been investigated with time-resolved two-photon photoemission spectroscopy (2PPE). Two excited electronic states at 2.4 and 3.6 eV above EF are attributed to unoccupied states in the chromophores, which are populated via charge transfer from the metal substrate and exhibit lifetimes in the order of 100 fs. Additional to the ultrafast dynamics we observe a continuous change of the monochromatic 2PPE spectra on the time scale of hours. While at a photon energy of h ν=4.2 eV the SAM is irreversibly modified by the UV illumination, reversible changes attributed to photoisomerization occur at h ν=3.6 eV. The low cross-section of <10−22 cm2 is in accordance with earlier experiments where within the experimental error no photoresponse to UV light was observed.