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Updated: Jan 15, 2026

Author Spotlight: Unveiling the Potential of VSFG Microscopy in Studying Mesoscopically Heterogeneous Self-Assembled Structures
Published on: December 1, 2023
Origin of the nonresonant signal in sum-frequency vibrational spectroscopy at the water interface
1Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, P. R. China. zrh@iccas.ac.cn.
Abstract:
We theoretically investigate the origin of the nonresonant signal in sum-frequency vibrational spectroscopy (SFVS) in interfacial water. The ground and excited states of water molecules are calculated using density functional theory (DFT) and time-dependent DFT (TDDFT). Transition moments, including electric and magnetic dipole as well as electric quadrupole terms, are computed. The SFVS from the electric dipole contribution is evaluated considering molecular orientations from neural network-based molecular dynamics simulations. The results demonstrate that the nonresonant SSP SFVS is dominated by the electric quadrupole contribution, with negligible contributions from electric and magnetic dipole terms. Theoretical predictions align well with experimental SFVS measurements, underscoring the importance of quadrupole effects in interfacial spectroscopy.
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