The splitting of spectral lines into closely-spaced components when
the radiating substance is placed in a strong → magnetic field.
Distinction is made between the normal and
→ anomalous Zeeman effects, and also the
longitudinal and transverse Zeeman effects. In the normal
→ longitudinal Zeeman effect each spectral line
is split into two components with frequencies ν ± Δν.
In the normal → transverse Zeeman effect
un un-displaced line is observed along with a doublet, i.e. three lines in all,
with the frequencies ν and ν ±Δν. In the classical theory
of the normal Zeeman effect, the motion of an electron in an atom is regarded as
the harmonic oscillation of a linear harmonic oscillator. Arbitrary linearly polarized
oscillation of the electron can be resolved into two oscillations: one along
the magnetic field and the other in a plane perpendicular to this field. The latter
can be further resolved into two oscillations, circularly polarized with opposite
directions of rotation that occur in the Larmor precession frequency. Classical theory
cannot explain the anomalous Zeeman effect. Both effects are accounted for in
quantum mechanics as the result of changes in the energy levels of atomic
electrons due to the interaction of their
→ orbital angular momentum and
→ spin angular momentum with each other
and with the external magnetic field.
See also → inverse Zeeman effect.
See also: Named after Pieter Zeeman (1865-1943), Dutch physicist who discovered the phenomenon;
→ effect.
