17O NUCLEAR MAGNETIC RELAXATION IN AQUEOUS SOLUTIONS OF DIAMAGNETIC METAL IONS

Measurements are reported on the transverse relaxation of oxygen-17 of water in solutions of diamagnetic electrolytes. For the 2+ ions it is shown that the effective correlation time for the quadrupole relaxation of waters in the first coordination sphere is appreciably shorter than the tumbling time for the hydrated ion. The data can be explained if the waters rotate randomly around the metal-oxygen axis in a time short compared to the tumbling time of the hydrated ion. This intramolecular rotation lowers considerably the effective quadrupole coupling. The model implies that corresponding effects should be present in proton and deuterium relaxation in water, and evidence is cited which is consistent with this prediction.