Deuteron Magnetic Resonance Study of Barium Chlorate Monohydrate

<jats:p>Quadrupole splitting of deuteron magnetic resonance was measured for a single crystal of Ba(ClO3)2·D2O. Quadrupole coupling, asymmetry parameter, and principal axis directions of the field gradient tensor were determined at 20° and at —130°C. eqQ/h=121.5±0.4 kc/sec, η=0.976±0.007 at 20°C, and eqQ/h=243.5±1.5 kc/sec, η=0.074±0.002 at —130°C. The field gradient at room temperature shows a rapid reorientation of the water molecule in a crystal. At room temperature, the spectral line exhibits fine structure due to coupling of two spins, which was utilized to determine the sign of eqQ in the present case.</jats:p> <jats:p>The line broadening effect in the intermediate temperature region (—45°∼—121°C) was measured and was used to obtain the reorientation rate at various temperatures. The barrier to reorientation of 6.6 kcal/mole was obtained from the comparison of the experimentally determined reorientation rate with that calculated from a tunneling process through a hindering barrier, or that of 6.5 kcal/mole from classical process. The temperature dependence of quadrupole splitting was also measured and the oscillation frequencies were derived for the torsional motion of D2O. It was found that the quadrupole coupling for a vibrationless molecule is about 12% less than that of a free molecule.</jats:p> <jats:p>The observed eqQ, principal axis directions of field-gradient tensor are discussed in connection with the disposition of atoms in the crystal. A qualitative explanation is given for the change of eqQ from a free molecule to that in the crystal as due to the effect of the hydrogen-bonded oxygen atom.</jats:p>