Define Stark’s effect.

Stark effect refers to the phenomenon where the spectral lines of atoms or molecules are shifted and split due to the presence of an external electric field. This effect is analogous to the Zeeman effect, which involves the splitting of spectral lines in a magnetic field. Named after Johannes Stark, who discovered it in 1913, the Stark effect can be observed in both emission and absorption spectra. It provides valuable information about the electric field environment around atoms or molecules and has significant applications in spectroscopy, quantum mechanics, and various fields of physics and chemistry.