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 Angstrom 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.