Raman spectroscopy is a non-destructive optical technique, based on scattering of light
Atoms in a molecule move about their equilibrium position in so called vibrational modes. When a particle of light (a photon) and a molecule interact, some of the energy of the photon can be transferred to the molecule.Thereby, one of the vibrational modes in the molecule is excited.
The energy of the scattered photon is reduced by the exact amount of energy received by the molecule.
Sir C.V. Raman discovered this light-scattering phenomenon in 1928 and was awarded the Nobel Prize in Physics in 1930.
In Raman spectroscopy the sample or object under investigation is illuminated with monochromatic laser light and the difference in energy between scattered photons and incident photons (called the “Raman-shift” and expressed in relative wavenumbers:
The precise amount of energy required to excite a molecular vibration, is sharply defined. It depends on the masses of the atoms involved in the vibration, on the type of chemical bonds between these atoms, on the structure of the molecule and on interactions with its environment and other molecules.