Nuclear Magnetic Resonance
Nuclear Magnetic Resonance takes advantage of the magnetic nature of hydrogen atoms and the fact that a hydrogen nucleus can be either pointing up or down, and that the energy levels are different depending on which way it's pointing. If you put a hydrogen atom in a magnetic field it's spin is up or down in relationship to the magnetic field. If the atoms spin is up it has slightly more energy, and it would like to shed it. If the spin is up in the magnetic field (aligned) then the nucleus has slightly more energy and if it's spin is down then the nucleus has slightly less energy.
The nucleus will tend to enter into a lower energy state, and it will do this by emitting a photon that has a sufficiently long wavelength that it's in the radio range. Though the FCC keeps KTEK from transmitting an active signal we are pleased to note that Workman 195 is broadcasting loud and clear.
However, with a constant magnetic field, not for long. All the hydrogen atoms you put in a magnetic field will quickly transition down to a lower energy, so we vary the field to keep them jumping up and down, and to keep them emitting. We use a permanent magnet and an electromagnetic capable of putting out one Tesla worth of magnetic fields. For comparison, that's 1/10th of the magnetic field of Jupiter.
Though this is an incredibly simple experiment, in which the most sophisticated piece of measurement equipment used is a radio, it is none-the-less an extremely accurate way to discover the magnetic moments of atoms. Later on in the experiment these techniques are used to measure the magnetic moment of unknown nucleuses. Though the identity of the nucleases is classified and I would have to kill you if I told you what they were let me assure you that it is indeed a thrill to attain them.