Abstract:
Nuclei with spin greater than 1/2 possess a quadrupole moment Q. This describes the departure from spherical symmetry of the distribution of positive charge within the nucleus. If such a nucleus is placed in an inhomogenous electric field, different (quantised) orientations of the quadrupole moment Q, with respect to the electric field gradient q, give rise to different energy levels. The energies of these levels are given by simple functions of eQq, the quadrupole coupling constant, where e is the protonic charge. Transitions between the available energy levels can be induced by electromagnetic radiation in the radiofrequency region.
