Proton and Deuteron Magnetic Resonance Study of Calcium Bromate Monohydrate

Abstract

The proton magnetic resonance spectrum of calcium bromate monohydrate was obtained. Results indicate that there are two orientations of the water molecule in the crystal. The p–p distances are 1.58 ± 0.02 and 1.59 ± 0.02 Å, respectively. Their orientations with respect to the crystallographic axes were determined. The protonic spin–lattice relaxation times were measured as functions of orientation at room temperature and of temperature in a single crystal of calcium bromate monohydrate. The b crystallographic axis was the axis of rotation of the crystal. The relaxation time was essentially independent of orientation of the crystal in the external magnetic field. The temperature dependence was characteristic of 180° flipping motion of the H2O molecule whose activation energy was 6.7 ± 0.4 kcal/mole. Quadrupole splittings of the Larmor resonance for the deuterons in Ca(BrO3)2·D2O were measured for single crystals at room temperature. The D2O molecules execute flipping motion at this temperature. The coupling constants and asymmetry parameters for both nonequivalent D2O molecules were determined to be 124.0 ± 1.5 kc/sec and 0.759 ± 0.015, respectively. No dipolar splittings of the quadrupole lines were observed. The H2O molecules were determined to be hydrogen bonded to the O(5) and O(2) atoms in the crystal.