effect

Stark effect

The Stark effect is the splitting of spectral lines in atoms due to an external electric field.
4 related articles

Description

In 1913, German physicist Johannes Stark discovered that in a strong electric field, hydrogen lines split and shift. Unlike the Zeeman effect, where the magnetic field breaks rotational symmetry, the electric field directly polarizes the atom. Classical physics could not explain the magnitude of the splitting; success came with quantum theory, where for hydrogen the shift depends linearly on the field (linear Stark effect). In multi-electron atoms, the interaction is usually quadratic.

History

Johannes Stark discovered the effect in 1913 by observing the splitting of hydrogen Balmer series lines in a strong electric field. The quantum mechanical explanation was given by Paul Epstein and Karl Schwarzschild in 1916, using separation of variables in the Schrödinger equation in parabolic coordinates. Subsequently, the effect became an important tool for plasma diagnostics and the development of optoelectronic devices.

How it works

The effect is used for light modulation in electro-optic modulators, where applied voltage controls absorption in semiconductor structures (quantum-confined Stark effect). In spectroscopy, Stark broadening of lines determines the concentration of charged particles in plasma. Limits of applicability: in strong fields, ionization occurs (fields above 10⁸ V/m), in weak fields, the effect is masked by Doppler broadening.

In practice

Optical modulators, semiconductor research, quantum-confined structures, spectral analysis of electric fields in plasma.

Fun fact

Near high-voltage power lines, electric fields are so strong that they cause a measurable shift in the spectral lines of air glow — the Stark effect can be seen in the lab without touching the wires.

Concept graph →

Related articles · 13

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