Most of us have seen the rainbow-hued breakdown of the composition of light. Light, of course, is a form of energy. A magnetic field changes the behavior of light — a phenomenon known as the Zeeman effect.
The Zeeman effect occurs when a spectral line (one of those little lines you see in a rainbow band of light) is split into varying frequencies as light enters a magnetic field. At the MagLab, the Zeeman effect is central to the data collected by the Electron Magnetic Resonance (EMR) group.
Dutch physicist Pieter Zeeman made his namesake discovery in the late 1800s. He noticed that powerful magnetic currents would widen the convergences of units of sodium under intense heat. Further analysis demonstrated the extension was a clear separation of spectral lines into more than a dozen entities. Such an occurrence is known as the "anomalous Zeeman effect." (The anomalous Zeeman effect actually occurs more often than the common effect.)
The breakthrough resulted in Zeeman receiving the 1902 Nobel Prize for Physics with former instructor Hendrik Antoon Lorentz. Lorentz, also a Dutch physicist, helped lay the groundwork for Zeeman's research with his own work on the ways magnetism influences the behavior of light.
Laboratory uses of the Zeeman effect center on spectral analysis and the quantification of magnetic field strength. Since the gap between the sections of the spectral line is proportional to the field power, the Zeeman effect is especially useful when magnetic field can't be quantified by more straightforward means.
The Zeeman effect has assisted physicists in verifying the energy levels in atoms and categorizing their mass and spin. It's also a useful way to evaluate atomic particles and electron paramagnetic resonance, and is essential in nuclear magnetic resonance spectroscopy.