NMR study of ammonium reorientation motion in NH4Br at high pressure

Measurements of spin-lattice relaxation time T-1 have been performed for po lycrystalline ammonium bromide as a function of hydrostatic pressure and te mperature. Activation parameters for NH; ion reorientation as functions of pressure were obtained. A two-well potential model is proposed for descript ion of ammonium reorientation motion. On the basis of the proposed model an d obtained activation data the libration frequency of the ammonium ion as a function of pressure was calculated and good agreement between experiment and calculation was obtained.