An incoherent quasi-elastic neutron scattering study on the dynamics of aqueous Cr3+perchlorate solutions

The technique of high-resolution, incoherent quasi-elastic neutron scattering (IQENS) is applied to a 1.790 molal (mol kg-1) solution of Cr(ClO4)3 at 26+or-1 degrees C. The results are consistent with a dynamic hydration number of six water molecules, each having a Cr3+-water-proton binding time described by the limit tau 1>or approximately=5*10-9 s. The results do not show a second shell of water protons in slow exchange with the cation, which implies a Cr3+ to second-shell water-proton binding time that is <5*10-9 s. Values for the water-proton translational self-diffusion coefficients are presented.