Ion hydration under pressure.
The pressure dependence of the radial distribution of water oxygen atoms around Rb+ and Br- ions in a diluted RbBr aqueous solution has been investigated by means of x-ray absorption spectroscopy at the Br and Rb K edges up to 2.8 GPa, using a large-volume high-pressure setup developed at a third generation synchrotron radiation facility. Dramatic effects in the anion hydration structure, in particular, are observed, indicating that upon increasing pressure water undergoes a structural transformation which involves considerable molecular reorientation.
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