Proton and Deuteron NMR of Ice Polymorphs

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Abstract
Proton and deuteron nuclear magnetic resonances in the H2O and D2O ice polymorphs have been recorded at 60 MHz and at 8 MHz, respectively. Proton rigid-lattice second moments have been obtained at 75°K for ices Ih, Ic, II, V, VI, and IX. The modulation-corrected experimental values of the second moments ranged from 32.2 G2 in ice Ic to 37.9 G2 in ice VI. Theoretical inter- and intramolecular contributions to the second moments of these ices have been made, with corrections applied to the latter for librational and vibrational motions after the manner of Pederson. These theoretical results when compared with experimental values strongly support the bent hydrogen-bond model with an H–O–H angle near 104°, in agreement with conclusions reached from our recent neutron-diffraction pattern analyses of ices Ic, II, and IX. Deuteron quadrupole coupling constants for ices Ic, II, V, and IX have been estimated from derivative of dispersion traces by comparison with the ice Ih signal obtained under similar experimental conditions. Because of saturation effects, it was not possible to record deuteron resonances at the temperature of liquid nitrogen; however, signals were recorded at temperatures slightly below the respective phase-transition temperatures for these ice polymorphs. From the relatively constant values of e2qQ / h observed for these ices, it appears that the O–D bond distance is essentially unchanged in the different ice forms. This generalization is also supported by the results of neutron-diffraction studies.

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