Motion of the H2O Molecule in Barium Chlorate Monohydrate

Abstract

When NMR is used for the study of the structures of molecules in solids the effects of molecular motion often must be considered. In the past those persons using proton magnetic resonance to study hydrates have not taken into account possible torsional vibration of the H₂O molecule. The Das theory predicts a significant effect upon proton doublet splitting by this motion. This work reports study of the Das effect in Ba(ClO₃)₂·H₂O as functions of crystal orientation and temperature. It was found that there is a change in doublet splitting that has the theoretical orientation dependence and the proper relative temperature dependence. However, the doublet splitting shows a zero‐point effect that is much smaller than that predicted. The reduction in splitting is about 1 G when the temperature of the hydrate changes from —79° to 94°C. Possible reasons for the lack of agreement between theory and experiment at very low temperatures are discussed.