# Proton-proton nuclear Overhauser effect as a probe for symmetry-preserving relaxation in oriented molecules

Rukmani, K and Kumar, Anil (1989) Proton-proton nuclear Overhauser effect as a probe for symmetry-preserving relaxation in oriented molecules. In: Journal of Magnetic Resonance, 85 (3). pp. 448-456.

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## Abstract

Difference nuclear Overhauser effect (NOE) experiments on oriented acetone and 2,1, 3-benzoselenadiazole, containing $A_3A'_3$ and AA'BB' spin systems, respectively, show that in the case of the former, NOE transfer is restricted to within a given irreducible representation while in the case of the latter, transfer from symmetric to antisymmetric representation does occur. Two possible mechanisms of relaxation in such systems, the intramolecular dipole-dipole and the external random field, were investigated and it was seen that in general the dipole-dipole mechanism does not restrict NOE transfer to a given representation. However, special geometry could restrict NOE transfer to transitions of the same representation. On the other hand a fully correlated external random field does restrict NOE transfer to one representation. Detailed theoretical calculations of the NOE in AA'BB' show good fit with the experiment for $\omega {\tau}_m \sim 2.0.$

Item Type: Journal Article Copyright of this article belongs to Elsevier Inc. Overhauser effect;Nematic solvent;Irreducible representation;NMR spectrum;Molecular orientation;Dipole-dipole interaction;Intramolecular interaction;Symmetry group;Random field;Theoretical study;Experimental study;Organic compounds;Magnetic relaxation;Selenium nitrogen heterocycle;Bicyclic compound;Saturated aliphatic compound;Ketone;Acetone Division of Physical & Mathematical Sciences > Physics 04 Dec 2007 19 Sep 2010 04:41 http://eprints.iisc.ernet.in/id/eprint/12742