Fine structure in the pure quadrupole resonance of oxygen-17 in Ba(ClO3)2⋅H2 17O by nuclear double resonance

Abstract

A technique of double resonance in the laboratory frame is applied for the measurement of the pure quadrupole resonances of oxygen-17 in polycrystalline Ba(ClO3)2⋅H2 17O at 77°K. The spectrum comprises three frequency bands displaying fine structure that is interpreted in terms of the intramolecular dipolar interactions within the hydration water molecule. The experimental results are compared with theoretical spectra calculated for various geometries of the water molecule and relative orientations of the quadrupolar and dipolar interactions. It is not possible to obtain a complete agreement between the calculated and experimental spectra, since apparently not all predicted lines show experimentally. It is suggested that the transitions involving triplet eigenstates of the proton–proton dipolar interaction are not observed, presumably due to excessive line broadening. Based on this assumption a good fit with the experimental spectrum is obtained with the following parameters: e2qQ/h (17O) = (−7.61±0.01)MHz, η=0.94±0.01, proton–oxygen distance ROH= (0.99±0.02) Å, and the HOH angle 2ϑ=110°±2°. These results are discussed in terms of the electronic and geometric structure of the hydration water molecule.