ABSTRACT
Atoms consist of nuclei and electrons that carry positive and negative charges, respectively. Movement of electric charges generates a magnetic field. Electrons and nuclei can therefore have a magnetic moment, originating from a circular electric current, and can be regarded as tiny magnetic dipoles. The positive charge of nuclei is located on the protons, and all nuclei except hydrogen contain more than one proton. In the presence of an external magnetic field, however, the magnetic dipole of a nucleus adopts certain orientations relative to the direction of the field. The electrons of the molecule shield its nuclei from the external magnetic field, rendering the local magnetic field slightly smaller than the external field. The sensitivity of the chemical shift to the environment can be exploited to map binding sites for ligands in chemical shift perturbation experiments.
