This shift in frequency is designated as a Stokes shift . If the final vibrational state is less energetic than the initial state, then the inelastically scattered photon will be shifted to a higher frequency, and this is designated as an anti-Stokes shift . Raman scattering is an example of inelastic scattering because the energy and momentum transfer between the photons and the molecules during the interaction results in a difference in energy between the incident and scattered photons.
