 Autler–Townes effect

In spectroscopy, the Autler–Townes effect (also known as AC Stark effect), is a type of dynamical Stark effects corresponding to the case when an oscillating electric field (e.g., that of a laser) is tuned in resonance (or close) to the transition frequency of a given spectral line, and resulting in a change of the shape of the absorption/emission spectra of that spectral line.The AC stark effect was discovered in 1955 by American physicists Stanley Autler and Charles Townes.