 Magnetic resonance

Magnetic resonance is a resonantly driven transition between states whose energy separation depends on a magnetic field. A static field splits magnetic substates through the Zeeman effect, while an oscillating transverse field supplies energy near the transition frequency. For a simple spin with gyromagnetic ratio $\gamma$, the angular resonance frequency is ${\omega }_0=|\gamma |B_0$.

In the Rabi molecular beam magnetic resonance experiment, inhomogeneous magnets selected and refocused molecular trajectories. A radio-frequency field changed magnetic substates at resonance, altering the transmitted beam intensity. Scanning the frequency therefore measured magnetic moments through a frequency-dependent signal.^[ref]