Proton NMR linewidths and second moments, and spin-lattice relaxation
times in the laboratory (12 and 60 MHz) and in rotating frames (H-1 =
9 x 10(-4) T) were studied for polycrystalline guanidinium nitrate ove
r a temperature range covering three solid phases. An analysis of the
experimental results enabled us to reveal a complex cation motion and
derive the respective activation parameters. In the low-temperature ph
ase a proton motion in the hydrogen bond has been demonstrated and cha
racterized. A convergence of two reorientational correlation times of
the guanidinium cation has been discovered at the first-order phase tr
ansition.