The chlorine-NQR and the deuteron-NMR relaxation have been investigated in (${\mathrm{ND}}_{\mathit{x}}$${\mathrm{H}}_{4\mathrm{-}\mathit{x}}$${)}_2$${\mathrm{SnCl}}_6$ (x=0,0.4) in the temperature range 4–300 K. Besides the large cross-relaxation maximum observed in both natural and partially deuterated compounds at about 55 K the ${}_{}{}^{35}{}_{}{}^{}\mathrm{NQR}$ relaxation rate shows two smaller maxima at 20 and 30 K in the deuterated salt only. These maxima are shifted to a higher temperature for ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$ isotope. The peak at 30 K has a corresponding tunneling channel in the ${}_{}{}^2{}_{}{}^{}\mathrm{NMR}$ relaxation rate. Deuteron spin-lattice relaxation rates, measured at 13.86 and 52.37 MHz, besides the level-crossing maxima, also show classical maxima related to molecular motions against a barrier about 15% of the full potential. All these effects are caused by limited jumps in a substructure at the bottom of the potential.

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