Raman frequency noncoincidence effect of confined liquid dimethyl sulfoxide

Raman spectroscopy was used to study the short-range structure of liquid dimethyl sulfoxide (DMSO) confined to porous silica glasses in the pore radius range from 15 to 56 A. By analyzing isotropic and anisotropic Raman spectra of DMSO in the SO stretching vibration region, we found the noncoincidence of the in-phase and out-of-phase SO vibrational wavenumbers increasing with decreasing pore radius. This behavior is in contrast to that found earlier for other confined polar liquids. Using a theory derived by Logan and results of ab initio calculations, the liquid structures of DMSO, acetone, N,N-dimethyl formamide in the proximity of silica surfaces are proposed. (C) 1999 American Institute of Physics. [S0021-9606(99)70145-5].