From Glossary of Meteorology
A shift in the energy levels of an isolated atom or molecule as a consequence of an external electric field.
Energy levels depend on the internal forces that electrons and nuclei exert on each other as well as on any external forces (e.g., an electromagnetic field). An observable consequence of the Stark effect is the shifting and broadening of spectral lines. The Stark effect is the electrical analogue of the Zeeman effect.