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Bulk Contributions Modulate the Sum-Frequency Generation Spectra of Interfacial Water on Model Sea-Spray Aerosols

preprint
submitted on 29.12.2017 and posted on 03.01.2018 by Sandeep K. Reddy, Raphael Thiraux, Bethany A. Wellen Rudd, Lu Lin, Tehseen Adel, Tatsuya Joutsuka, Franz M. Geiger, Heather C. Allen, Akihiro Morita, Francesco Paesani
Vibrational sum-frequency generation (vSFG) spectroscopy is used to determine the molecular structure of water at the interface of palmitic acid monolayers. Both measured and calculated spectra display speci c features due to third-order contributions to the vSFG response which are associated with nite interfacial electric potentials. We demonstrate that theoretical modeling enables to separate the third-order contributions, thus allowing for a systematic analysis of the strictly surface-sensitive, second-order component of the vSFG response. This study provides fundamental, molecular-level insights into the interfacial structure of water in a neutral surfactant system with relevance to single layer bio-membranes and environmentally relevant sea-spray aerosols. These results emphasize the key role that computer simulations can play in interpreting vSFG spectra and revealing microscopic details of water at complex interfaces, which can be difficult to extract from experiments due to the mixing of second-order, surface-sensitive and third-order, bulk-dependent contributions to the vSFG response.

Funding

National Science Foundation

History

Topic

  • Photochemistry (Physical Chem.)
  • Interfaces
  • Spectroscopy (Physical Chem.)

Email Address of Submitting Author

fpaesani@ucsd.edu

Institution

University of California San Diego

Country

United States

ORCID For Submitting Author

0000-0002-4451-1203

Declaration of Conflict of Interest

No conflict of interest

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