Temperature‐ and pressure‐dependent study of ³⁵Cl NQR frequency and spin lattice relaxation time in 2,3‐dichloroanisole

Abstract

The temperature and pressure dependence of (35)Cl NQR frequency and spin lattice relaxation time (T(1)) were investigated in 2,3-dichloroanisole. Two NQR signals were observed throughout the temperature and pressure range studied. T(1) were measured in the temperature range from 77 to 300 K and from atmospheric pressure to 5 kbar. Relaxation was found to be due to the torsional motion of the molecule and also reorientation of motion of the CH(3) group. T(1) versus temperature data were analyzed on the basis of Woessner and Gutowsky model, and the activation energy for the reorientation of the CH(3) group was estimated. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities were also obtained. NQR frequency shows a nonlinear behavior with pressure, indicating both dynamic and static effects of pressure. The pressure coefficients were observed to be positive for both the lines. A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency. The variation of spin lattice time with pressure was very small, showing that the relaxation is mainly due to the torsional motions of the molecules.

35Cl NQR frequency and spin lattice relaxation study in 3,4‐dichloronitrobenzene as a function of temperature and pressure

“…By following the similar procedure used by Ramu et al and Suresh et al, the NQR data has been analyzed using Equations , and . The moment of inertia values are taken from the literatur .…”

“…The molten solid of mass about 2 g is taken in a glass ampoule of 10‐mm diameter and sealed to avoid hydration of the sample. Measurements of NQR frequency and spin lattice relaxation time (T 1 ) have been carried out using the set up described earlier in the temperature range 77 to 300 K. Two lines were observed throughout the temperature range studied and the frequency values at 77 K are in good agreement with those reported in the literature…”

“…Bayer proposed the first theoretical model to explain the temperature dependence of T 1 , which was later modified by Woessner and Gutowsky by defining an average lifetime for all the torsional states and obtained W 1 and W 2 for the Δm = ±1 and Δm = ±2 transitions. In the present case, we have followed the methods used by Ramu et al and Suresh et al for the analysis of spin lattice relaxation time.…”

“…The second term, the “dynamic term,” represents the effect of pressure on the amplitude of torsional oscillation. The methods followed for the analysis of pressure variation of NQR frequency is as described in the paper by Ramu et al and Suresh et al…”

Assessment of substituent effects on the parameters of 35Cl nuclear quadrupole resonance in para‐substituted benzene‐sulphenyl chloride via quantum chemical calculations

“…The first NQR measurements were reported for a solid using signals from 35 Cl in transdichloroethylene . 35 Cl NQR parameters of the many molecules were investigated for illustration of the structural details and the variations in the electronic environment of the nucleuses . In one study, correlation of 35 NQR coupling frequencies for some chlorobenzene has been investigated …”