EFFECT OF HYDROSTATIC-PRESSURE ON CATION REORIENTATION IN PYRIDINIUM IODIDE

Measurements of second moment of H-1 NMR line, spin-lattice relaxation time and complex permittivity have been performed for polycrystalline pyridinium iodide as a function of hydrostatic pressure and temperatu re. The influence of pressure on molecular reorientation of the pyridi nium cation was analysed. The occurrence of reorientations between the potential energy minima of different depths in the low-temperature ph ase was confirmed. With increasing pressure the height of the E-B barr ier was found to increase while that of the E-C barrier and asymmetry parameter Delta was found to decrease.