Raman Spectroscopy
Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down.

Raman spectroscopy is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. raman spectrometry is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified.

Raman spectroscopy relies upon inelastic scattering of photons, known as raman spectrometry. A source of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range is used, although X-rays can also be used. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy typically yields similar, complementary, information.

The Raman Spectroscopy Principle

When light interacts with molecules in a gas, liquid, or solid, the vast majority of the photons are dispersed or scattered at the same energy as the incident photons. This is described as elastic scattering, or Rayleigh scattering. A small number of these photons, approximately 1 photon in 10 million will scatter at a different frequency than the incident photon. This process is called inelastic scattering, or the Raman effect, named after Sir C.V. Raman who discovered this and was awarded the 1930 Nobel Prize in Physics for his work. Since that time, Raman has been utilized for a vast array of applications from medical diagnostics to material science and reaction analysis. Raman allows the user to collect the vibrational signature of a molecule, giving insight into how it is put together, as well as how it interacts with other molecules around it.

Advantages of Raman Spectroscopy

• Many organic and inorganic materials are suitable for Raman analysis.                                  
• Samples can be solids, liquids, polymers or vapours.
• No sample preparation needed.
• Not interfered by water.
• Non-destructive.
• Highly specific like a chemical fingerprint of a material.
• Raman spectra are acquired quickly within seconds.
• Samples can be analysed through glass or a polymer packaging.
• Laser light and Raman scattered light can be transmitted by optical fibres over long distances for remote analysis.
• The region from 4000 cm-1 to 50 cm-1 can be covered by a single recording.
• Raman spectra can be collected from a very small volume (< 1 μm in diameter).
• Inorganic materials are easily analysable with Raman spectroscopy.