Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 12: Ultrafast Electron and spin dynamics at interfaces II

O 12.6: Vortrag

Montag, 12. März 2018, 16:15–16:30, MA 005

The role of small polarons in ultrafast electron localization near a model electrolyte/metal interface — •Sarah King, Katharina Broch, and Julia Stähler — Department of Physical Chemistry, Fritz-Haber Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

In the current study, we investigate the formation dynamics of small polarons in thin films of dimethyl sulfoxide (DMSO) near a Cu(111) metal interface using time- and angle-resolved two-photon photoemission spectroscopy. A delocalized electronic state within the second DMSO monolayer is initially formed upon photoexcitation and dynamically becomes a small polaron in DMSO on a 200 fs timescale, consistent with localization due to vibrational dynamics of the DMSO film. The polaron is subsequently further stabilized through longer-range screening on a 600 fs timescale. As the small polaron formation dynamics are the same for both 6 ML and 2 ML of DMSO, the mechanism observed in our experiments is relevant to bulk DMSO near metal surfaces. Furthermore, the small polaron acts as a precursor state for a surface-bound electronic state with a lifetime thirteen orders of magnitude longer. This highlights the way in which electronic states near metal surfaces with femtosecond lifetimes are important precursors for long-lived states of solvents and electrolytes.