PROTON AND DEUTERON MAGNETIC RESONANCE IN PARTLY DEUTERATED CRYSTALS .3. GYPSUM

Single crystals of gypsum containing approximately 50 per cent deuterium have been made by heating natural gypsum crystals in heavy water at 110°C for 24 hr. The room temperature D(euteron)MR- and P(roton)MR-spectra of these partly deuterated crystals have been analyzed in detail. The water molecules are flipping fast at room temperature making the two deuterons in each molecule magnetically equivalent. The quadrupole coupling constant has been found to be 118.3 ± 0.7 kHz and the asymmetry factor 0.877 ± 0.009. The directions of the principal axes are closely related to the orientation of the water molecule as given by neutron diffraction. From the hyperfine structure in the DMR-spectra and the second moments of the PMR-spectra the mole fractions of H2O, HDO and D2O molecules in the crystal are derived. The deuteron distribution in the crystal is found to be different from a random distribution on the available sites. The data indicate that the molecular distribution within the crystal is random, but intermolecular proton-deuteron exchange does not seem to take place inside the crystal to a measurable extent. © 1969.