By applying both a magnetic field and carefully tuning a radio-frequency tranmitter, the nuclear spins will flip, in an effect known as the Rabi cycle, allowing the concentration of such nuclei to be measured.
By applying both a magnetic field and carefully tuning a radio-frequency transmitter, the nuclear spins will flip and re-emit radiation, in an effect known as the Rabi cycle. The strength and frequency of the emitted radio waves allows the concentration of such nuclei to be measured.