SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 37: Poster: Ultrafast Electron Dynamics at Surface and Interfaces II

O 37.2: Poster

Dienstag, 28. März 2023, 18:00–20:00, P2/EG

Pump-probe second harmonic spectroscopy of molecule/metal interfaces — Jinghao Chen¹, Rui Shi², Ping Zhou¹, Uwe Bovensiepen¹, Wolfgang Hübner², Georg Lefkidis², and •Andrea Eschenlohr¹ — ¹Faculty of Physics and CENIDE, Uni Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany — ²Department of Physics, TU Kaiserslautern, Box 3049, 67653 Kaiserslautern, Germany

Achieving a microscopic understanding of charge transfer dynamics and the relaxation of optically excited electrons and holes at molecule/metal interfaces requires an interface-sensitive analysis on the respective femtosecond timescales. Second harmonic spectroscopy (SHS) is such an interface-sensitive probe in centrosymmetric materials. We perform pump-probe SHS in the visible wavelength range (1.9-2.5 eV) with <20 fs pulse duration. A prototypical molecule/metal interface is prepared by adsorption of iron octaethylporphyrin (FeOEP) molecules on Cu(001) and analyzed in situ in ultrahigh vacuum. By comparison with first principles theory, we identify a molecule-induced resonance at about 2.2 eV fundamental photon energy in the SHS of one monolayer of FeOEP/Cu(001). At this resonance, we observe a markedly slower relaxation time of the pump-induced changes in SHS compared to the bare Cu(001) surface, which indicates an increased lifetime of the electronic molecular state.

We thank H. Wende, J. Güdde and E. Riedle for valuable experimental advice, and the German Research Foundation for funding via SPP 1840 QUTIF and Sfb 1242.