Term: shielding constant, \(\sigma\)
https://doi.org/10.1351/goldbook.S05645

Definition:
In NMR the difference between the external magnetic flux density and the local magnetic flux density at a resonating nucleus affected by the neighbouring electrons divided by the external flux density, σ = B 0- B B 0.

Related Terms:
1) magnetic flux density (http://doi.org/10.1351/goldbook.M03686).
2) nucleus (http://doi.org/10.1351/goldbook.N04256).

Source: Green Book, 2nd ed., p. 25 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)

Citation: 'shielding constant, \(\sigma\)' 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.S05645

License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.

Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.