Stokes line is named after Sir George Gabriel Stokes. It is the radiation of particular wavelengths present in the line spectra associated with fluorescence and the Raman scattering. Stokes lines are of longer wavelength than that of the exciting radiation responsible for the fluorescence or Raman effect. Sir George Gabriel Stokes, 1st Baronet (August 13, 1819 – February 1, 1903) was an Irish mathematician and physicist. ... Raman scattering or the Raman effect is the inelastic scattering of a photon which creates or annihilates an optical phonon. ...

The energy of the scattered radiation is less than the incident radiation for the Stokes line and the energy of the scattered radiation is more than the incident radiation for the anti-Stokes line. The energy increase or decrease from the excitation is related to the vibrational energy spacing in the ground electronic state of the molecule and therefore the wavenumber of the Stokes and anti-Stokes lines are a direct measure of the vibrational energies of the molecule.

Also see Raman effect, Stokes shift When light is scattered from a molecule most photons are elastically scattered. ... 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. ...