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35 Cl NQR frequency and spin lattice relaxation time in 3,4-dichloronitrobenzene have been measured as a function of temperature and pressure. Two NQR signals were observed in the temperature range 77 to 300 K and pressure up to 5.1 kbar at 300 K. The contributions to the relaxation from the torsional motion of the molecule and reorientational motion of the nitro group have been analyzed on the basis of the Woessner and Gutowsky model. The temperature dependence of the average torsional lifetimes of the molecules, transition probabilities, and the activation energy for the reorientation of the nitro group was estimated. The pressure dependence of the NQR frequency in 3,4-Dichloronitrobenzene shows a nonlinear increase in NQR frequency with increase in pressure, indicating increased contribution from the static effects at higher pressures. A thermodynamic analysis of the data was carried out to determine the constant-volume temperature coefficients of the NQR frequency. The spin-lattice relaxation was found to be weakly dependent on pressure., (© 2019 John Wiley & Sons, Ltd.)

The pressure dependences of (35)Cl nuclear quadrupole resonance (NQR) frequency, temperature and pressure variation of spin lattice relaxation time (T(1)) were investigated in 3,4-dichlorophenol. T(1) was measured in the temperature range 77-300 K. Furthermore, the NQR frequency and T(1) for these compounds were measured as a function of pressure up to 5 kbar at 300 K. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities W(1) and W(2) for the Δm = ±1 and Δm = ±2 transitions were also obtained. A nonlinear variation of NQR frequency with pressure has been observed and the pressure coefficients were observed to be positive. A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency. An attempt is made to compare the torsional frequencies evaluated from NQR data with those obtained by IR spectra. On selecting the appropriate mode from IR spectra, a good agreement with torsional frequency obtained from NQR data is observed. The previously mentioned approach is a good illustration of the supplementary nature of the data from IR studies, in relation to NQR studies of compounds in solid state., (Copyright © 2012 John Wiley & Sons, Ltd.)

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., (2010 John Wiley & Sons, Ltd.)