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:
“When you consider the radiance, that it does not withhold
itself but pours its abundance without selection into every
nook and cranny”
—Archie Randolph Ammons (b. 1926)
“As no one can tell what was the Roman pronunciation, each nation makes the Latin conform, for the most part, to the rules of its own language; so that with us of the vowels only A has a peculiar sound.”
—Henry David Thoreau (1817–1862)