Zeeman splitting
= Zeeman splitting
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{wiki=Zeeman_effect}
= Zeeman effect
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{synonym}
Zeeman splitting is the separation of <energy> levels or mode <frequencies> by a background <magnetic field>. In <atomic physics>, the <magnetic field> couples to a <magnetic dipole moment>, lifting <quantum degeneracy>. Transitions between the shifted <quantum states> can turn one <spectral line> into several. A split level and a split <spectral line> are different objects: the emitted <photon> measures the difference between two level <energies>, and the <electric-dipole selection rule> determines which differences appear.
The <Stern-Gerlach experiment> also probes <magnetic dipole moments>, through beam deflection in a <magnetic field> gradient. Here the readout is a <spectral line>.
The pattern makes an invisible <magnetic field> visible through <spectroscopy>. It also reveals <angular momentum> and <magnetic dipole moments> inside <chemical atoms>. <Zeeman slowers> exploit a changing resonance <frequency> to keep moving <chemical atoms> absorbing <laser> <photons>; a <magneto-optical trap> combines position-dependent shifts with <electromagnetic polarization> and <laser cooling>. Related mode shifts occur in <Zeeman splitting of an antiferromagnetic spin wave>.