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.

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