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O: Fachverband Oberflächenphysik

O 51: Focus Session: Structure and Dynamics of Solvent at Electrochemical Interfaces II

O 51.2: Vortrag

Dienstag, 10. März 2026, 15:00–15:15, TRE/MATH

Second-order nonlinear vibrational spectroscopy: from depth-resolved studies at charged aqueous interfaces towards determining excitonic-vibrational coupling in hybrid heterostructures — •Debojyoti Roy, Sarabjeet Kaur, Álvaro Díaz Duque, Martin Wolf, Alexander P. Fellows, and Martin Thämer — Fritz-Haber-Institut of the Max Planck Society, 14195 Berlin, Germany

The properties of charged aqueous interfaces are governed by interfacial electric fields that influence ion distributions in the liquid phase, forming an electric double layer. While the evolution of the electric potential is relatively well described by theoretical models, much less is known about the influence of the DC fields on the interfacial molecular structure of water and its evolution with depth. Using our recently developed combined sum- and difference-frequency generation spectroscopy (SFG/DFG), we investigate the depth-dependent water structure at charged interfaces as a function of ionic strength, obtaining deep insight into the anisotropic orientational distribution of water and detailed information on the properties of the hydrogen bond network at different distances from the phase boundary.

Besides depth-resolution, the complementary information from SFG and DFG responses can also be used to isolate coupling terms in doubly-resonant studies. Here we also explore this possibility conceptually and propose such studies on exciton-vibrational coupling in 2D material/organic interfaces, which have various applications in solar cells but still lack understanding of their physicochemical properties.

Keywords: nonlinear vibrational spectroscopy; charged aqueous interfaces; excitonic–vibrational coupling; phase resolved SFG\DFG spectroscopy; 2D hybrid heterostructures