A Pulsed ³⁵Cl NQR Study on the Molecular Motions and Phase Transition of 4-Chlorobenzyl Alcohol

Abstract

The spin-lattice and spin-spin relaxation times T t and T 2 of 35 C1 NQR were measured for the high (I) and low (II) temperature phases of 4-chlorobenzyl alcohol in the range 50< T/K <338 (transition and melting points: 236 and 343.5 K, respectively). In phase II the T x behavior in the range 50< T/K<90 can be explained by lattice vibrations and that in the range 90<T/K<190 by reorientation with an activation energy of ca. 3.8 kJ/mol. In phase I, the T x behavior at T>260 K is explainable by another reorientation with £ a %4.7 kJ/mol. The T, vs. T curves revealed that in both phases the crystal dynamics is anomalous in the vicinity of the transition temperature. Lattice defects accumulated in phases I and II by the phase transition were found to be responsible for the extremely short inverse line width parameters (7^).