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O: Fachverband Oberflächenphysik

O 28: Solid-Liquid Interfaces II: Structure and Spectroscopy

O 28.1: Talk

Tuesday, March 19, 2024, 10:30–10:45, H 1012

Just How Anisotropic is the Air-Water Interface? An SFG/DFG Study — •Martin Thämer¹, Alexander Fellows¹, Álvaro Díaz Duque¹, Vasillios Balos², Louis Lehmann³, Roland Netz³, and Martin Wolf¹ — ¹Fritz-Haber-Institut der MPG, Berlin, Germany — ²IMDEA Nanociencia, Madrid, Spain — ³Freie Universität, Berlin. Germany

The air-water interface belongs to the most abundant interfaces on our planet and its unique properties are at the heart of numerous chemical processes in both nature and industrial applications. However, despite decades of research, some of the most fundamental aspects of the air-water interface still remain controversial, particularly the thickness of the interfacial region.

Here we directly address this question by employing our recently developed depth-resolved vibrational spectroscopy, which is based on the simultaneous measurement of phase-resolved sum- and difference-frequency signals and allows for precise depth-profiling on the sub-nm scale. Through isotopic exchange experiments the second-order spectra are separated into their resonant and non-resonant contributions, allowing the origins of each to be determined along with the length-scales of their decaying contributions. These results provide the first direct experimental measurement of the anisotropic layer thickness and yield important insight into the different signal contributions in second-order spectroscopy on water.

Keywords: Water Interface; SFG/DFG spectroscopy; Depth Profiling