Erlangen 2018 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 21: Advanced Time-Resolved Spectroscopy

MO 21.5: Vortrag

Donnerstag, 8. März 2018, 15:00–15:15, PA 2.150

Structure and dynamics of water at the electrolyte solution-air interface studied with pump-probe SFG — •Malte Deiseroth, Sudipta Das, Mischa Bonn, and Ellen H.G. Backus — Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz

Physical and chemical processes occurring at salt-water-air interfaces play a prominent role in a variety of fields ranging from the chemistry of atmospheric aerosols and heterogeneous catalysis to biophysics and biochemistry. Knowledge of the molecular interfacial structure and energy flow dynamics at these interfaces is important, not only for a fundamental understanding of this ubiquitous liquid but also to understand its reactivity.

Here, we report a surface-sensitive sum-frequency generation (SFG) spectroscopy study of the interface of electrolyte solutions with air, aimed at obtaining information about the molecular arrangement of water and ions at the interface, and how this affects energy dissipation at the interface. Time-resolved and 2D pump-probe spectroscopy provide insights into dynamics of interfacial water molecules with sub-picosecond time resolution. Substantial differences are observed between the static SFG spectra obtained from the surface of solutions of Na₂SO₄, Na₂CO₃, and pure water, pointing to large variations in the interfacial structure of these different solutions; remarkably, the vibrational dynamics of these systems are indistinguishable. Hence, while electrolytes clearly restructure the interface of water, the vibrational dynamics is unaffected by the structural changes.