Raman non‐coincidence effect of the carbonyl stretching mode in confined polar liquids

The Raman non‐coincidence effect of the symmetric C=O stretching band was measured in liquid acetone and N,N‐dimethylformamide confined to porous silica glasses prepared by the sol—gel process. The experiments were carried out both on bulk liquids and liquids confined to glasses with pore radii from 17—76 Å at 293 K. The value of the non‐coincidence was decreased with decreasing pore radius (R) and scaled approximately as 1/R. Additional information about the role of pore surface effects was obtained by measurements on the polar liquids confined to surface‐modified glasses when the surface hydroxyl groups were replaced by OSi(CH3)3 groups. The experimental data show that the non‐coincidence effect is independent of the pore size in surface‐modified glasses.