Dynamical Properties of Water in Nickel (II) Hexafluorosilicate (IV) Hexahydrate NiSiF6.6H2O Below 300 K Probed by Raman Spectroscopy

Raman spectra of NiSiF66H2O have been measured between 300 and 10 K. The Raman band due to vibrations of the water molecules in the solid shows an exponential variation of the half-width with temperature which is interpreted as due to thermally activated re-orientation of the water. This activation energy is significantly lower than the barrier height to water re-orientation measured by dielectric relaxation and we interpret the activation energy as the energy of the first excited vibrational level of the water.