X-ray diffraction and Raman spectroscopy investigations in concentrated aqueous solutions of yttrium and strontium nitrates

X-ray diffraction experiments on concentrated aqueous solutions of yttrium and strontium nitrates seem to demonstrate that a local order concerning the cations themselves exists. Molecular models built to interpret these experiments suggest that a disturbance of the quasi-close-packing of the cations is more marked for these nitrate solutions than for aqueous solutions of halide salts of the same cations. Raman spectra of both solutions show a multiple structure of some bands assigned to the internal vibrational motions of the nitrate anion in agreement with what was observed by Mathieu and Lounsbury for strontium nitrate solutions. A tentative interpretation of this result is proposed.