SAE NMR is a probe of the change in the quadrupolar precession frequency (! Q ) over time for a specific nucleus with a spin I > 1/2, such as 7 Li, which has a nuclear spin of I = 3/2. For the nucleus of a single Li atom, ! Q is extracted from the EFG tensor V, which describes the interaction between the quadrupole of the nucleus and its surrounding electric field. The EFG tensor is the second positional derivative of the electric field V around the nucleus,