nuclear Overhauser effect symbol: η

Synonym: nuclear Overhauser enhancement
Initialism: nOe
https://doi.org/10.1351/goldbook.08385
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 (Io). ηi(S)=(I−Io)/Io. The effect may be given as a percentage η×100 %.
  2. nOe allows a measure of through space rather than through bond interactions between nuclei and is proportional to the inverse 6th power of the internuclear distance.
  3. η 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 [Terms] [Paper]
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. https://doi.org/10.1351/goldbook.08385 RIS BibTex EndNote
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