NMR relaxation study of rotational motion in low-barrier ammonium salts

The temperature dependence of the proton spin-lattice relaxation times T1 and T1/g9 for polycrystalline (NH4)2RuCl6, (NH4)2PdCl6 and (NH4)2PtCl6, shows that the ammonium reorientation is the dominant relaxation mechanism. In these salts, as for other low-barrier ammonium salts, the activation energies are small, as suggested by considerations concerning the lattice structure and symmetry.