Its discovery was the result of the first application of perturbation theory to quantum mechanics.  
This effect can be witnessed in a rotational microwave spectrometer, in which one looks for signal low J line transitions.  Its discovery was the result of the first application of perturbation theory to quantum mechanics.  This effect, generally not symmetric like its magnetic counterpart, occurs when an atom becomes polarized and the resulting dipole moment interacts with the electric field.  Analogous to the Zeeman effect, FTP, identify this effect that results in the splitting of an atom's energy levels by an electric field.
This effect can be witnessed in a rotational microwave spectrometer, in which one looks for signal low J line transitions.  
Stark effect