Raman spectrum

Dependence on molecular symmetry

Molecular vibrational modes can be categorized as Raman "active" or "inactive" depending on whether they contribute to the Raman spectrum or not. For a vibrational mode to be Raman active, there must be a change between the polarizability of the initial and final states. This creates a fundamental connection between the symmetry of the molecular vibrational modes and the possibility, or impossibility, of observing them in the Raman spectrum. The symmetry of molecular vibration for a particular molecule can be assessed with an accurate molecular model, and molecules that share symmetries also share characteristic patterns in their Raman spectra.