Stokes shift

Stokes shift

Stokes shift is the difference (in wavelength or frequency units) between positions of the band maxima of the absorption and luminescence spectra of the same electronic transition.

When a molecule or atom absorbs light, it enters an excited electronic state. The Stokes shift occurs because the molecule loses a small amount of the absorbed energy before re-releasing the rest of the energy as luminescence. This energy is often lost as thermal energy.

It is named after Irish physicist George G. Stokes.

Also see Stokes line