Nuclear Magnetic Resonance on Oriented Nuclei

By applying a radio frequency signal to a cold source, it is possible to prompt transitions between the sublevels, thus reducing the anisotropy of the emitted radiation. For this to occur, the signal frequency must satisfy

h= B / I

In practice individual nuclei experience slightly different hyperfine fields, so it is necessary to apply a signal with a frequency modulation if a significant fraction of the nuclei is to be resonated. Scanning across a frequency range, a sharp resonance is seen when the above condition is satisfied. If the nuclear spin and hyperfine field are known, then the magnetic dipole moment can be measured to high precision.