DYNAMICS OF NITRITE IONS IN IONIC PLASTIC CRYSTAL RBNO2 STUDIED BY NITROGEN AND RUBIDIUM NMR

Temperature dependences of NMR spin-lattice relaxation times T-1 of N- 15, N-14, Rb-85 and Rb-87, spin-spin relaxation times T-2 of N-14 and Rb-87, and NMR spectra of N-15 and Rb-87 in RbNO2 were observed in the plastic phase (Phase I) and the low-temperature phase (Phase II) obta inable below 264 K. We showed the presence of a new NO2- motion in Pha se II with an activation energy of 12- 15 kJ mol(-1). This motion was assigned to NO2- reorientation about its C-2-axis by referring to the temperature dependence of the N-15 chemical-shift anisotropy and the r eported data of the dielectric dispersion. In the plastic phase, we de tected the NO2- isotropic reorientation with an activation energy of 6 .2 kJ mol(-1) and the ionic self-diffusion with 110 kJ mol(-1), which was confirmed by measuring electrical conductivity.