35/37Cl NQR and Raman investigations of molecular motions in (NH4)2SnCl6

The NQR frequency and the spin-lattice relaxation time of the isotopes 35Cl and 37Cl in (NH4)2SnCl6, have been investigated in the temperature range 4.2 K to 450 K. The anomalous temperature variation of the resonance frequency is attributed to the additional field gradient produced by the NH+4 ion. This contribution changes as the jump rate of the hindered rotation of the ammonium ion varies with temperature. Nowhere in the temperature range studied the relaxation rates follow a simple T2 behaviour. This might partly be due to the same mechanism.