Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 75: Ultrafast Electron and Spin Dynamics

O 75.10: Vortrag

Mittwoch, 22. März 2017, 17:15–17:30, TRE Phy

Ultrafast electron dynamics and small polaron formation in solid DMSO on Cu(111) — •Sarah King, Katharina Broch, and Julia Stähler — Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

The ultrafast electron solvation dynamics in DMSO have been investigated using time- and angle-resolved two-photon photoemission spectroscopy of condensed DMSO films on a Cu(111) single crystal with different coverages, between 1 and 10 monolayer (ML) equivalents. At DMSO coverages higher than 1 ML, initially a delocalized electronic state is formed in DMSO at 2.85 ± 0.05 eV relative to the Fermi level, with an effective mass of approximately 1.8 times the mass of a free electron. This state simultaneously undergoes localization and energetic stabilization where the peak energy shifts to lower energies at a rate of approximately 1 eV/ps as the peak dispersion flattens. By 200 fs after formation, this state exhibits negative dispersion and ten-fold slower peak shifting before decaying completely within 1 ps. We preliminarily attribute the dynamics in peak energy and localization to small polaron formation in DMSO. The decay-time of the small polaron state is concomitant with the rise-time in a DMSO/vacuum surface state at 2.30 ± 0.05 eV, which has an extremely long decay time of seconds and exhibits reactivity with oxygen. As DMSO is a common electrolyte, our results on non-equilibrium electronic states in DMSO are important for understanding electrochemistry.