A PULSED CL-35 NQR STUDY ON THE MOLECULAR MOTIONS AND PHASE-TRANSITION OF 4-CHLOROBENZYL ALCOHOL

The spin-lattice and spin-spin relaxation times T-1 and T-2 of Cl-35 N QR were measured for the high (I) and low (II) temperature phases of 4 -chlorobenzyl alcohol in the range 50 < T/K < 338 (transition and melt ing points: 236 and 343.5 K, respectively). In phase II the T-1 behavi or in the range 50 < T/K < 90 can be explained by lattice vibrations a nd that in the range 90 < T/K < 190 by reorientation with an activatio n energy of ca. 3.8 kJ/mol. In phase I, the T-1 behavior at T > 260 K is explainable by another reorientation with E(a) approximate to 4.7 k J/mol. The T-1 vs. T curves revealed that in both phases the crystal d ynamics is anomalous in the vicinity of the transition temperature. La ttice defects accumulated in phases I and II by the phase transition w ere found to be responsible for the extremely short inverse line width parameters (T-2).