Zeeman effect
![Zeeman splitting of the 5s level of Rb-87, including fine structure and hyperfine structure splitting. Here F = J + I, where I is the nuclear spin. (for Rb-87, I = 3/2)](/Images/godic/202501/20/Breit-rabi-Zeeman1344.png")
![This animation shows what happens as a sunspot (or starspot) forms and the magnetic field increases in strength. The light emerging from the spot starts to demonstrate the Zeeman effect. The dark spectra lines in the spectrum of the emitted light split into three components and the strength of the circular polarisation in parts of the spectrum increases significantly. This polarisation effect is a powerful tool for astronomers to detect and measure stellar magnetic fields.](/Images/godic/202501/20/-Explanation_of_how_the_magnetic_field_on_a_star_affects_the_light_emitted.webm1344.jpg")
![](/Images/godic/202501/20/Zeeman_p_s_doublet.svg1344.png")
![Zeeman effect on a sunspot spectral line](/Images/godic/202501/20/Sunzeeman19191345.png")
The Zeeman effect (/ˈzeɪmən/; Dutch pronunciation:[ˈzeːmɑn]), named after the Dutch physicist Pieter Zeeman, is the effect of splitting a spectral line into several components in the presence of a static magnetic field. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field. Also similar to the Stark effect, transitions between different components have, in general, different intensities, with some being entirely forbidden (in the dipole approximation), as governed by the selection rules.