Experimental Verification of the Theory of Nuclear Quadrupole Relaxation in Liquids over the Entire Range of Molecular Tumbling Motion

Nuclearmagneticresonance(NMR)spectraofquadrupolarnuclei(I>1/2)in liquids often consist of broad resonances, making it difficult to obtain useful chemical information. The poor NMR spectral resolution commonly observed for quadrupolar nuclei isadirectconsequenceofnuclearquadrupolerelaxationprocesses.Althoughallkeyaspectsof nuclear quadrupole relaxation processes have been known for decades within the framework of the Redfield relaxation theory, direct experimental NMR relaxation data that cover a wide range of molecular motion in liquids for quadrupolar nuclei are generally lacking. Here we reportacompletesetofexperimentalnuclearquadrupolerelaxationdatathatareobtainedfor 17 O, a half-integer quadrupolar nucleus, over the entire range of molecular motion within the limit of the Redfield theory. Ageneral approachutilizing the quadrupole relaxation properties in the slow motion limit will be particularly beneficial for studies of quadrupolar nuclei in biomolecules of medium and large sizes.