Zeeman and Stark Effects

Abstract

AbstractThe Zeeman and Stark effects are modifications of spectral lines (displacements, splittings, and polarization changes) induced respectively by magnetic and electric fields. Application of an external static field splits the energy levels of a degenerate multiplet of states. In the Zeeman effect, levels shift up or down in energy depending on the magnitude and sign of the magnetic quantum number; in the Stark effect the shift depends only on the magnitude of the magnetic quantum number. Resulting spectral line patterns depend on the relative size of the field‐induced level splittings compared to the separation between different multiplets. This article discusses the weak‐, strong‐, and ultrastrong‐field Zeeman effects (the latter case arising when the magnetic interaction is comparable to the binding energy), and the linear and quadratic (including “ac”) Stark effects. In highly excited atoms (Rydberg atoms), where the separation between distinct manifolds is small and the electric polarizability enormous, the full range of Zeeman and Stark effects can be induced by relatively low fields. These effects have been employed to probe atomic and molecular structure, to measure inaccessible (e.g., stellar and interstellar) fields, and to gauge the influence of stray external fields in high‐precision metrology.