Proton spin lattice relaxation by NH4+ ion motions and spin diffusion in some ammonium compounds

Abstract

The spin-lattice relaxation times (T1) of protons in polycrystalline diammonium-d-tartrate, (NH4)2C4H4O6, ammonium bismuth citrate, NH4BiC6H5O7, diammonium hydrogen citrate, (NH4)2HC6H5O7, sodium ammonium hydrogen phosphate tetrahydrate, NaNH4HPO4·4H2O, ammonium carbonate mohohydrate, (NH4)2CO3·H2O, ammonium thiosulfate (NH4)2S2O3 and hydroxylammonium chloride, NH3OHCl, have been measured as a function of temperature. The first two compounds have double minima but each of the latter exhibits a single minimum in T1. The results have been interpreted by considering the reorientational motions of the NH4+ ions and their role of behaving as sinks to rapid spin diffusion of the other protons in the compounds. The double minima in T1 for the first two compounds were attributed to the magnetically nonequivalent NH4+ ions in their unit cells. © 1984.