Lattice Imperfections and Relaxation of Cl NQR in Chloral Iso-Butylhemiacetal

Abstract

Abstract The temperature dependence of the S/N ratios of three 35Cl NQR lines (v1, v2 , v3) in chloral iso-butylhemiacetal shows interesting features in the range 77-300 K. 35Cl T1 indicates that above 220 K reorientation of CCl 3 is excited, and this results in a gradual decrease in S/N. The activation energy calculated from 35Cl NQR T1 results is 30 kJ mol-1 for v1 and v2 but 25 kJ mol -1 for v 3 . The difference seems to be attributable to the motion of H in the OH group. A minimum of 35Cl NQR T2 is found around 180 K but 35Cl T1 shows no anomaly. 35Cl T2 determines the S/N ratios in the range between 130-220 K. The line broadening below 130 K is attributable to an inhomogeneity of the electric field gradient at resonant nuclei produced by lattice defects.