Structural investigation of water and aqueous
solutions by Raman spectroscopy*
F. Rull
Unidad Asociada al Centro de Astrobiologia, INTA-CSIC;
Cristalografia y Mineralogia, Facultad de Ciencias, Universidad de Valladolid,
Valladolid, Spain
Abstract: In the context of a long study of the dynamical properties
of water and inorganic aqueous solutions using infrared (IR) and Raman
spectroscopy,we present here recent results of the influence of salt
concentration on the dynamics of water molecules. The main systems studied
were salts of XnYm type (where X = Li+,
Na+, K+, Rb+, Cs+, Mg2+,
Zn2+ and Y = Cl–,ClO4–,
NO3–, SO4–2).
The whole spectrum reflects the molecular and ionic interactions between
solvent molecules and solvent–solute and solute–solute molecules. Nevertheless,
each spectral region supplies different information about these intermolecular
interactions.
The strong modifications in intensity and band profile undergone by
the v(OH) band depends mainly on the nature of anions while cations
have a weak influence. A picture of these different situations in a
particular salt solution needs the support of a model of the dynamic
structure of the water solvent. A discussion of the current state of
the dynamical models of liquid water and new ideas on water dynamics
are presented on the basis of the results obtained from the study of
internal OH/OD vibrations of water in diluted mixtures of D2O/H2O.
Finally, a comparative analysis of the influence on the dynamics of
water molecules under the concentration of perchlorate and chloride
salts of monovalent cations in water and isotopic D2O/H2O
mixtures was undertaken using Raman spectroscopy.
* Lectures presented at the 10th International Symposium
on Solubility Phenomena, Varna, Bulgaria, 22 -26 July 2002. Other
lectures are published in this issue, pp. 1785-1920.
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