Abstract
The spin–lattice relaxation times of protons in polycrystalline hydrazine dichloride, N2H6Cl2, hydrazine dinitrate, N2H6(NO3)2, hydrazine hydrate, N2H6O, and hydrazine sulphate, N2H6SO4, have been measured at 60 MHz as a function of temperature between 140 and 450 K. T1 passes through a minimum of 21.6 ms for each of the first three compounds. However, T1 for hydrazine sulphate exhibits anomalous behaviour at low temperatures: it usually passes through a minimum of 47 ms but in some experiments through a minimum of 27 ms. The temperature dependence of T1 was found to be characteristic of a dominant relaxation mechanism, reorientational motion of NH+ 3 groups about the N—N bond direction. The experimental value (T1)min= 21.6 ms agrees exactly with the estimated value for the first three compounds. However, all the experimental T1 results cannot be fitted by assuming an Arrhenius dependence of correlation times and this has been attributed to a decrease in activation energies with increasing temperature.

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