A level-crossing relaxation study of ND4+ion tunnelling frequencies in ND4ClO4and (ND4)2PtCl6

Deuteron spin-lattice relaxation time T 1 was measured in ND 4 ClO 4 and (ND 4 ) 2 PtCl 6 at frequencies from 4 to 7 MHz and for the temperature range from 1.7 to 40K. Shallow level-crossing minima were revealed in the frequency dependence, allowing the tunnelling splittings between the A and E symmetry levels to be estimated as about 6.2 MHz and 10.8 MHz for ND 4 ClO 4 and (ND 4 ) 2 PtCl 6 , respectively. The shape of the free induction decay was observed to depend on the resonance frequency and was found to be much shorter at the level-crossing minima for ND 4 ClO 4 . Activation energies of 3.2 and 3.6 kJ mol -1 were obtained for ND 4 ClO 4 and (ND 4 ) 2 PtCl 6 respectively.