Dynamical structure of water in dioxane aqueous solution by low-frequency Raman scattering

The low-frequency Raman spectra of dioxane aqueous solutions have been analyzed from a dynamical aspect of water structure. The reduced Raman spectra x9( n̄) of the dioxane aqueous solutions are well explained by a superposition of three characteristic modes of water and one Gaussian mode ~;60 cm! of dioxane. The concentration dependence of x9( n̄) spectra shows that the 190 cm mode of water disappears below about 0.8 molar fraction of water. This molar fraction corresponds to the ratio of four water molecules to one dioxane molecule. This means that the tetrahedral-like structure of water which is formed by five water molecules is almost destroyed below about 0.8 molar fraction. Thus the basic idea of the five water molecules model of liquid water has been confirmed from Raman spectroscopic point of view. © 1996 American Institute of Physics. @S0021-9606~96!51319-9#