Raman spectroscopy studies of liquids confined to porous silica glasses

Raman spectroscopic experiments are presented to investigate the dynamics and structure of liquids confined to porous silica glasses. Using dimethyl sulfoxide (DMSO) as an illustrative example, it is reported that the vibrational correlation time of the SO stretching vibration in DMSO is decreased by confinement and scales with the reciprocal pore radius. This result is interpreted on the basis of a two-state model for surface and bulk molecules. The different contributions to the SO vibrational relaxation are discussed. Furthermore, using the noncoincidence of the isotropic and anisotropic Raman frequencies of the SO vibrational mode, which is a result of an intermolecular vibrational coupling, the surface layer structure of DMSO in pores of silica glass is derived