Spin–lattice relaxation of protons in some polycrystalline ammonium compounds

Abstract

The temperature dependence of the spin–lattice relaxation times of protons in polycrystalline ammonium bromide (NH₄Br), ammonium thiocyanate (NH₄SCN) ammonium nitrate (NH₄NO₃), ammonium peroxydisulphate [(NH₄)₂S₂O₈], ammonium dichromate [(NH₄)₂Cr₂O₇] and ammonium cerium nitrate [(NH₄)₂Ce(NO₃)₆] have been investigated using a pulse technique at 60 MHz. Discontinuities in the spin-lattice relaxation times against temperature plots have been observed and it is concluded that the spin–rotational interactions of NH⁺₄ ions contribute to the spin–lattice relaxation at elevated temperatures. The spin–lattice relaxation of some of the compounds exhibits a minimum at low temperatures; experimental results are in good agreement with theory.