## shielding constant, $$\sigma$$

https://doi.org/10.1351/goldbook.S05645
In NMR the difference between the external @M03686@ and the local @M03686@ at a resonating @N04256@ affected by the neighbouring electrons divided by the external flux density, $$\sigma =\frac{B_{0}\,-\,B}{B_{0}}$$.
Source:
Green Book, 2nd ed., p. 25 [Terms] [Book]