Phase-sensitive sum frequency vibrational spectroscopic study of air/water interfaces: H2O, D2O, and diluted isotopic mixtures

Xiaofan Xu; Y Ron Shen; Chuanshan Tian

doi:10.1063/1.5081135

Phase-sensitive sum frequency vibrational spectroscopic study of air/water interfaces: H₂O, D₂O, and diluted isotopic mixtures

J Chem Phys. 2019 Apr 14;150(14):144701. doi: 10.1063/1.5081135.

Authors

Xiaofan Xu¹, Y Ron Shen¹, Chuanshan Tian¹

Affiliation

¹ Department of Physics, State Key Laboratory of Surface Physics and Key Laboratory of Micro- and Nano-Photonic Structures (MOE), Fudan University, Shanghai 200433, China.

PMID: 30981245
DOI: 10.1063/1.5081135

Abstract

Using phase-sensitive sum-frequency vibrational spectroscopy with a carefully chosen phase reference, we revisited the vibrational spectra of vapor/water interfaces of neat H₂O and D₂O as well as HDO in diluted isotopic mixtures. Using z-cut quartz as the phase reference, with proper frequency scaling, the gross features of the OH and OD stretching spectra from H₂O and D₂O and from HDO in two isotopic mixtures look similar and agree with those reported earlier, but differences are also apparent. In particular, a weak positive band at low frequencies, which has been asserted by molecular dynamic simulations but not detectable in the experimental OH spectrum with pure H₂O, is now visible in the OD spectrum. The differences must arise from the change of intermolecular interaction of water molecules with their surrounding molecules upon exchange of the isotopes.