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Quadrupole splitting of the deuteron magnetic resonance was measured in single crystals of solid D2O at —10°C. For deuterons on the hexagonal crystal axis, eQq1/h equaled 213.2±0.8 kc/sec, and | η1 | was equal to 0.100±0.002. For the other deuterons, eQq2/h was found to be equal to 216.4±1.0 kc/sec. No change in the line separations was observed at a temperature of —70°C. No evidence was found for hindered rotation of the D2O molecules nor for intermolecular deuteron transfer at —10°C. Lower limits to the barriers hindering these motions were estimated; these limits permit estimates to be made of hydrogen-bond energies. The coupling constants in the solid are about 30% less than those reported for the free molecule. Most of this decrease must be ascribed to electronic structural changes brought about as a result of hydrogen-bond formation.

Several pulsed NMR experiments using rapidly repeating pulse sequences are described. Theoretical results for magnetization as a function of pulse spacing T are given for cases where the Bloch equations apply, and compared with experiments. These results suggest a simple method of rapid signal accumulation when T 2*

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4600L. C. HOSKINS Ref. 2J. The actual computations were carried out by using an iteration procedure written for the IBM 1620 computer. The error limits in the force constants were set by arbitrarily admitting an error of ±0.4 cm-l in the P-R separations.The differences between the force constants of this work and those of Levin and Abramowitz are not solely due to interpolation errors and choices of structural parameters. Because of deviations of the theoretical and observed sum rules, the latter authors chose their force field as midway between that which reproduced .\3 and that which reproduced '\4, with the uncertainties in the force constants being set by estimated errors in the zeta values. In this work the force field was chosen as that which reproduced .\4 exactly, .\3 being set by the sum rule.The interaction force constants F34 for these Group V triflourides are clearly negative, being smallest for NF3 and approximately equal for PF 3 and AsF 3 . The bending force constant F44 decreases from NF3 to AsF3, but the F33 constant is largest for PFa and smallest for NFa.Besides the work by Levin and Abramowitz 3 and Hoskins and Lord,2 the only other attempt which has been made to determine the interaction constants of Group V trifluorides was made by Mirri et al. 16 using rotational distortion constants of PF3. Their value of F 34 = -0.677 mdyn is not consistent with the results using Coriolis coupling data, and an interaction force constant of this magnitude cannot result from uncertainties in the zetas. Their force constants for PFa are therefore probably in error.Deuterium magnetic resonance spectra of polycrystalline NDa have been observed at 75°, 159°, and 185°K. The measured values of e'qQlh were IS6±7 kc/sec at 75°K, and 72.5±0.9 kclsec at 159° and 185°K. The decrease at the higher temperatures has been attributed to rotational averaging. Single-crystal growth in the polycrystalline matrix was noted at the higher temperatures; it did not seriously interfere with the measurement of e 2 qQlh. Proton second-moment measurements were made on a polycrystalline sample of NHa at 75°K. The moment obtained was intermediate between the moments expected for the cases of fast and slow Ca reorientation. The rotational-transition temperature has been estimated to be 72°±2°K. A lower limit of 1.75 kcal/mole for the reorientational activation energy was estimated. An anomalous absorption peak was recorded in the center of the NDa spectrum at 75°K. It may possibly be ascribed to a double-quantum transition.