Sum-frequency vibrational spectroscopy of interfacial water under Fermi resonance

We present the investigation of sum-frequency vibrational spectroscopy (SFVS) for interfacial OH stretching modes, employing a mixed quantum/classical approach coupled with artificial neural network-based molecular dynamics simulations. This study provides an explicit account of electric dipole effects under Fermi resonance, which couples the bending overtone with the fundamental stretching mode. Our results reveal that Fermi resonance modulates the spectral features of stretching-mode SSP SFVS. The findings provide new molecular-level insights into the vibrational coupling mechanisms at water interfaces and represent an important advancement in interpreting surface-specific vibrational spectra.