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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.

The Zeeman effect of chlorine nuclear quadrupole resonance in polycrystalline samples of 2,6-, 2,5 and 3,5-dichloro.phenol has been investigated at room temperature in order to study the effect of hydrogen bonding on the electric field gradient asymmetry parameter q. While the two n.q.r. lines in 3,5dichlorophenol gave an asymmetry parameter of x 10 %, those in 2,6-and 2,5-dichlorophenol gave different values of q for the two chlorines. The chlorine atom which is ortho to the OH group and involved in hydrogen bonding (k, corresponding to the low frequency line) gave an asymmetry parameter of0.21 in 2,6dichlorophenol and 0.17 in 2,5-dichlorophenol while the other chlorine ( i e . , corresponding to the high frequency line) gave a lower value of 0.12 in 2,6-dichlorophenol and 0.11 in 2,5-dichlorophenol. These values of q are discussed in terms of hydrogen bonding and bond parameters.

An ESR study of centres in x-irradiated ammonium perchlorate single crystals is carried out that is aimed at resolving the controversy that has recently arisen over the possible occurrence of low-temperature phase transitions in the compound (room temperature structure: orthorhombic; space group Pnma). The ESR spectra are recorded as a function of the orientation of the magnetic field H in the three orthogonal crystallographic planes at 300 K, 77 K, and 4.2 K, and also as a function of temperature for H parallel to the principal z-component of the hyperfine coupling tensor. The analysis of the spectra shows that while the -tensor remained axial over the entire temperature range 2.0052(3), 2.0055(3), 2.0057(3) and 2.0090(3), 2.0096(3), 2.0105(3) at 300 K, 77 K, and 4.2 K respectively), , which is rhombic at room temperature , , and at 300 K) becomes more axial as the temperature is lowered , , and at 77 K, and , , and at 4.2 K). No changes in the spectra attributable to any phase transition were observed, and we conclude that does not undergo any phase transition below room temperature. Furthermore, it is found that during radiative decomposition the mirror-related Cl - O bonds, even though weaker than the other Cl - O bonds, do not break, thus confirming our earlier conclusion that mirror symmetry is preserved during radiation damage.

Key words zirconium nitride/silicon thin films, dc reactive magnetron sputtering, optical constants, electrical resistivity. PACS 81.15.Cd, 68.55, 78.66 This paper deals with the preparation of Zirconium Nitride films by DC reactive magnetron sputtering. Films were deposited on silicon substrates at room temperature. Nitrogen partial pressure was varied from 4x10 -5 to 10x10-5 m bar and the effect on the structural, electrical, optical properties of the films was systematically studied. The films formed at a nitrogen pressure of 6x10 -5 mbar showed low electrical resistivity of 1.726x10 -3 Ω.cm. The deposited films were found to be crystalline with refractive index and extinction coefficient 1.95 and 0.4352 respectively.