Chemical shielding tensor is a matrix describing the interaction between a nuclear spin and an external magnetic field in situations when this interaction is directionally anisotropic. It is a generalization of the concept of chemical shift that moves away from the historical conventions used in chemical shift reporting, and puts the concept on a rigorous quantum mechanical foundation.
Derivation edit
Consider the total energy of a molecular system placed into a magnetic field . The contribution from the interaction between the magnetic dipole of a specific nucleus and the field is very weak (of the order of microjoules per mole), and the corresponding Taylor series may therefore be truncated at first order:
