In nuclear physics the g -factor of a given system includes the effect of the nucleon spins, their orbital angular momenta, and their couplings. Generally, the g -factors are very difficult to calculate for such many-body systems, but they have been measured to high precision for most nuclei. The Larmor frequency is important in NMR spectroscopy. The gyromagnetic ratios, which give the Larmor frequencies at a given magnetic field strength, have been measured and tabulated.