Vibrational sum-frequency generation (vSFG) spectroscopy is used to determine the molecular structure of water at a model sea-spray aerosol surface. Both measured and calculated spectra display specific features as a result of third-order contributions to the vSFG response, and these are associated with finite interfacial electric potentials. We demonstrate that theoretical modeling enables separation of 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 insights into the interfacial molecular organization and hydrogen-bonding structure of water, which mediate heterogeneous processes on sea-spray aerosols. Our results emphasize the key role that computer simulations can play in interpreting vSFG spectra and revealing microscopic details at complex aqueous interfaces, which can be difficult to extract from experiments because of the mixing of second-order, surface-sensitive, and third-order bulk-dependent contributions to the vSFG response.

振动和频产生（vSFG）光谱用于确定模型海喷雾气溶胶表面上水的分子结构。由于对vSFG响应的三次贡献，测量和计算的光谱均显示特定特征，并且这些特征与有限的界面电势相关。我们证明了理论建模可以分离三阶贡献，从而可以对vSFG响应的严格表面敏感的二阶成分进行系统分析。这项研究提供了对水的界面分子组织和氢键结构的基本见解，它们介导了海喷雾气溶胶的异质过程。