Selection Rules
The distortion of a molecule in an electric field, and therefore the vibrational Raman cross section, is determined by its polarizability.
A Raman transition from one state to another, and therefore a Raman shift, can be activated optically only in the presence of non-zero polarizability derivative with respect to the normal coordinate (that is, the vibration or rotation):
Raman-active vibrations/rotations can be identified by using almost any textbook that treats quantum mechanics or group theory for chemistry. Then, Raman-active modes can be found for molecules or crystals that show symmetry by using the appropriate character table for that symmetry group.
Read more about this topic: Raman Scattering
Famous quotes containing the words selection and/or rules:
“Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species.”
—Konrad Lorenz (1903–1989)
“A man often thinks he rules himself, when all the while he is ruled and managed; and while his understanding directs one design, his affections imperceptibly draw him into another.”
—François, Duc De La Rochefoucauld (1613–1680)