TRIPLET CORRELATIONS IN THE HYDRATION SHELL OF AQUAIONS

The presence of angular O-ion-O correlations in the hydration shell of dilute water solutions of Cu2+ and Br- is investigated by means of an X-ray absorption experiment. An advanced data analysis including multiple-scattering effects produced quantitative information on these triplet correlations; the complementarity with X-ray and neutron diffraction is discussed. The experimental spectra indicate that Cu2+ has a Jahn-Teller distorted octahedral coordination, while the hydration shell of Br- is more disordered and substantially dominated by excluded volume effects