DYNAMICAL PROPERTIES OF WATER-METHANOL SOLUTIONS STUDIED BY DEPOLARIZED RAYLEIGH-SCATTERING

The dynamics of water in water-methanol solutions is studied by depola rized Rayleigh light scattering as a function of concentration and tem perature. The obtained data give evidence of a well-defined maximum il l the hydrogen bonding relaxation time at equimolar concentration. Thi s phenomenon is consistent with the presence of well-defined shells of water around the methanol molecules as observed recently by means of a neutron diffraction experiment. In addition, our data show that the water rotational relaxation time increases with increasing solute conc entration. This suggests that the water structure in these shells is m ore stable than bulk water structure at the same temperature.