Temperature Features of Hydration of Singly-Charged Ions as Studied in A Diffusion NMR Experiment

Abstract

The concentration dependences of the self-diffusion coefficients of water molecules in water solutions of a series of 1–1 electrolytes at different temperatures determined using nuclear magnetic resonance (NMR) with a magnetic field gradient are analyzed. The relevant results show that the hydration sign for Cs⁺, I⁻, Rb⁺, Br⁻, K⁺, and Cl⁻ ions changes at temperatures characteristic for each ion. These characteristic temperatures are determined for the ions and KI, KBr, KCl, CsF, LiI, KF, LiCl, NaCl, RbCl, and Li₂SO₄ water solutions. The temperature dependence of the $\tau _{0} /\tau _{{1i}}$ ratio of the lifetime of water molecules in the structure of bulk water $\tau_{0}$ to their lifetime in the structure of hydrated shells $\tau_{1i}$ of Cs⁺, I⁻, Rb⁺, Br⁻, Cl⁻, K⁺, Na⁺, F⁻, and Li⁺ ions (i) is studied.