The dynamics of water molecules in ionic solution. II. Quasi-elastic neutron scattering and tracer diffusion studies of the proton and ion dynamics in concentrated Ni²⁺, Cu²⁺and Nd³⁺aqueous solutions

Abstract

For pt.I see ibid., vol.20, p.1573 (1987). The technique of high-resolution incoherent quasielastic neutron scattering (QENS) is used to measure the translational diffusive motion of water protons in concentrated NiX2, CuX2 and NdX3 aqueous solutions in which X=Cl-, ClO4- and/or NO3-. The technique of tracer diffusion is also used in order to measure the cation selfdiffusion coefficient in concentrated NiX2 and CuX2 aqueous solutions in which X=Cl- and ClO4-. It is shown that at room temperature ( approximately=25 degrees C) the cation-water proton binding times are described by the limits tau 1(Ni2+)>or approximately=5*10-9 s, tau 1(Cu2+)<or approximately=10-10 s and tau 1(Nd3+)>10-10 s and that for the Ni2+ solutions, which are in slow exchange, the diffusion coefficient of protons bound to the cation is measurable using the QENS method.