Longitudinal relaxation rates of⁷Li in concentrated solutions of LiNO₃in 1,3‐diaminopropane in the liquid state

Abstract

The temperature and concentration dependencies of 7Li longitudinal relaxation have been investigated for concentrated solutions of LiNO3 in 1,3‐diaminopropane in the liquid state. The experimental longitudinal relaxation rates (R1) of 7Li are interpreted as the sum of the quadrupolar and the dipolar contributions. The dipolar contributions are estimated from the assumed local structure of solutions and the assumption that the correlation times of the quadrupolar and dipolar interactions are identical. Then, the quadrupolar contributions are separated from the experimental R1, values and described by the electric field gradient (EFG) at the 7Li nucleus and its reorientational correlation time (τ). The temperature dependence of τ deviated from a simple Arrhenius law over the temperature range studied. The composition dependence of τ and EFG show bends at around 30mol% LiNO3. This is consistent with the previous results obtained from the electrical conductance, and suggests that solvent molecules may act as bridges between Li+ ions at higher concentrations of LiNO3.