Abstract
The dynamic network structures of water molecules surrounding acetone molecule and DMSO molecule are investigated by low frequency Raman spectroscopy. Acetone molecule and DMSO molecule have very similar molecular structures with only one difference in the central atom; it is a carbon for acetone and is a sulfur for DMSO. These differences manifest themselves as the differences of dipole moment of each molecule which result in a very different behavior of their aqueous solutions. Observed Raman spectra are analyzed by the linear combination of Raman spectrum of pure water and that of pure solute. We found that besides the linear combination of two spectra the extra damped harmonic oscillation mode was required for the cancellation of the systematic deviation from observed spectra. It is also found that the extra oscillation mode shows strong solute dependence. Using this solute dependence of the extra oscillation mode, we found that acetone molecules promote the ordered structure of water molecules while DMSO molecules prevent the formation of the ordered structure of water molecules.
