Title: nuclear Overhauser effect
Long Title: IUPAC Gold Book - nuclear Overhauser effect
DOI: 10.1351/goldbook.08385
Status: current

Definition
Change of intensity of one resonance when the spin transitions of another are somehow perturbed from their equilibrium populations.

Notes
1) The nuclear Overhauser effect at nucleus \(i\) for perturbation of spin \(S\) is expressed as a relative intensity change between the equilibrium intensity (\(I\)) and that in the presence of the nOe (\(I_{\rm{o}}\)). \(\eta_{i}({\rm{S}}) = (I - I_{o})/I_{o}\). The effect may be given as a percentage \(\eta \times \pu{100 \%}\).
2) nOe allows a measure of through space rather than through bond interactions between nuclei and is proportional to the inverse \(6^{\rm{th}}\) power of the internuclear distance.
3) \(\eta\) can be positive or negative depending on the motional properties of the molecule and the signs of the gyromagnetic ratios.

Source
- PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 698 (https://doi.org/10.1515/pac-2019-0203)

Other Outputs
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- json: https://goldbook.iupac.org/terms/view/08385/json
- xml: https://goldbook.iupac.org/terms/view/08385/xml

Citation: Citation: 'nuclear Overhauser effect' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.08385
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Accessed: 2026-05-30T21:08:00+00:00