A. Cunsolo et M. Nardone, VELOCITY DISPERSION AND VISCOUS RELAXATION IN SUPERCOOLED WATER, The Journal of chemical physics, 105(10), 1996, pp. 3911-3917
Brillouin scattering spectra of water from T = 30 degrees C down to su
percooling temperatures of about T = -26 degrees C have been measured,
at different scattering angles and for different exciting wavelengths
, covering exchanged wave vector values from 0.0137 to 0.0351 nm(-1).
A fit of the spectra using the hydrodynamic line shape for a simple fl
uid confirms the existence of a relevant dispersion in the wave vector
dependence of the hypersonic sound velocity. The parameters obtained
fitting the data with a relaxing hydrodynamic model indicate the ratio
between volume and shear viscosity is almost temperature independent
also in the supercooled regime and that a single relaxation process, i
nvolving almost entirely both shear and volume viscosities, accounts f
or the observed dispersion. The infinite frequency sound velocity is f
ound to be of about 2150 m/s almost independently on temperature. The
temperature dependence of the relaxation time is discussed and compare
d with that of other relaxation times available in the literature. Pre
dictions are made for the temperature and wave vector values at which
the dispersion of sound velocity should be best observed. (C) 1996 Ame
rican Institute of Physics.