Mutual Exclusion Rule
Definition
For a centrosymmetric molecule (one with a centre of inversion), a vibration is either IR active or Raman active, never both. This rule is what makes IR and Raman strictly complementary for symmetric molecules like CO2 and benzene.
Related terms
- Polarisability
- The ease with which the electron cloud of a molecule deforms in an external electric field. A vibration is Raman active only...
- Raman Effect
- Inelastic scattering of monochromatic light by a molecule. The scattered photon is shifted in wavelength by an amount equal to a vibrational...
- SERS
- Surface-enhanced Raman scattering. A nanorough gold or silver surface enhances the Raman signal of molecules adsorbed on it by factors of 10^6...
- SORS
- Spatially offset Raman spectroscopy. The collection optics are offset from the laser spot so the detector reads photons that have travelled through...
- Stokes and Anti-Stokes Lines
- Stokes lines (longer wavelength, lower energy than the laser) come from molecules starting in the ground vibrational state; anti-Stokes lines (shorter wavelength,...
Explained in
- Raman Spectroscopy and Comparison with IRFor a centrosymmetric molecule (one with a centre of inversion), a vibration is either IR active or Raman active, never both. This rule is what makes IR and Ra...