shielding

Also contains definition of: deshielding
https://doi.org/10.1351/goldbook.S05644
In the context of NMR @[email protected] shielding is the effect of the electron shells of the observed and the neighbouring nuclei on the external magnetic field. The external field induces circulations in the electron cloud. The resulting magnetic moment is oriented in the opposite direction to the external field, so that the local field at the central @[email protected] is weakened, although it may be strengthened at other nuclei (deshielding). The phenomenon is the origin of the structural dependence of the @[email protected] frequencies of the nuclei.