Model of molecular reorientation in liquid water and anionic effect on Raman spectral data

New experimental data on O-H and O-D stretching vibrations were obtained from Raman studies on light and heavy water and some aqueous salt solutions. We estimate the previous results in (his field under new aspects, The mechanism of defect formation was suggested as rotational reorientation of the liquid water molecules by analogy with the rotational isomerism when hindered rotation around single bonds takes place. This point of view is true for H2O, HOD and D2O molecules. On the basis of our Raman spectra of light, heavy liquid water, HOD and aqueous solutions of various salts we report on non homogeneity of the spatial H-bond network of liquid water. The reason for that is the presence of defects of the H-bond network from the different conformations of fully hydrogen-bonded five-molecule structural units found in liquid water. The presence of each of them depends on temperature, pressure and solution concentration. Each component of the stretching water band meeting a corresponding confirmation can be separated in the Raman spectra of aqueous solutions by selection of different alkali metal halides. The frequencies and intensities of these components practically do not depend on the nature of the cation but on the nature and size of the anion of the dissolved salt. Our result suggests water molecule mobility across the defects of the H-bond network and not by defects of the liquid water structure often reported in literature.