Nuclear Relaxation and Spin Exchange in Ammonium Hexafluorophosphate (NH4PF6).

The three phases of solid ammonium hexafluorophosphate NH4PF6 have been studied by cw and pulsed NMR methods between 298 and 77K. The proton and fluorine second moments at 298K are consistent with rapid, randomized reorientations of NH4 and PF6- ions, while the larger values at 77K require that there be little or no motional narrowing by reorientations of the PF6- ions even though the narrowing by NH4 reorientations is still present. For both nuclear species the spin-lattice relaxation time T1 studies of the two low-temperature phases reveal three distinct regions Activation parameters for the PF6- reorientation were determined from the fluorine T1 in ND4PF6.