Why raman spectroscopy is used

Scanning Probing Microscopy. Where and Why should I use Raman Spectroscopy? Applications of Critical Point Drying. Raman Spectroscopy. In general it is not suitable for analysis of metals and their alloys, but could be very useful in many applications: Chemistry and Plastics Carbon materials Pharmaceutics Life sciences Geology Archaeology. Raman spectroscopy features the following advatanges over mid-IR, near-IR spectroscopy and other analyical techniques: No sample preparation No matter the sample is a solid, liquid, powder, slurry or gas; even translucent packing does not interfere.

Analyse through transparent containers and windows Most Raman analyses use visible or near-visible light. It is, therefore, simple to collect the content-rich information even when the sample is sealed within a transparent container e.

Sensitive to small changes in material structure Raman bands result directly from molecular vibrations. These vibrations are very sensitive to changes in chemistry and structure, so you can spot subtle differences in molecular environment.

The direct relationship between vibrations and Raman bands also makes interpretation easier. You can analyse samples in water You can analyse samples in aqueous solutions, such as suspensions or biological samples. There is no need for time-consuming extraction or drying, which may also alter the chemistry of your samples.

It works on almost all materials Almost all materials exhibit Raman scattering. The only exception is pure metals, which just reflect light. However metallurgists use Raman spectroscopy because carbides, nitrides and oxides do Raman scatter. It uses light Scientists and engineers can apply the tricks they already know about manipulating light to Raman spectroscopy. For example:. You can combine Renishaw's Raman systems with a host of other complementary analysis methods, such as:.

Raman who, together with his research partner K. Krishnan, was the first to observe Raman scattering in Raman spectroscopy extracts this information through the detection of Raman scattering from the sample.

When light is scattered by molecule, the oscillating electromagnetic field of a photon induces a polarisation of the molecular electron cloud which leaves the molecule in a higher energy state with the energy of the photon transferred to the molecule. This can be considered as the formation of a very short-lived complex between the photon and molecule which is commonly called the virtual state of the molecule.

The virtual state is not stable and the photon is re-emitted almost immediately, as scattered light. Figure 1 Three types of scattering processes that can occur when light interacts with a molecule.

In the vast majority of scattering events, the energy of the molecule is unchanged after its interaction with the photon; and the energy, and therefore the wavelength, of the scattered photon is equal to that of the incident photon.

This is called elastic energy of scattering particle is conserved or Rayleigh scattering and is the dominant process. In a much rarer event approximately 1 in 10 million photons 2 Raman scattering occurs, which is an inelastic scattering process with a transfer of energy between the molecule and scattered photon. If the molecule gains energy from the photon during the scattering excited to a higher vibrational level then the scattered photon loses energy and its wavelength increases which is called Stokes Raman scattering after G.

Inversely, if the molecule loses energy by relaxing to a lower vibrational level the scattered photon gains the corresponding energy and its wavelength decreases; which is called Anti-Stokes Raman scattering. Quantum mechanically Stokes and Anti-Stokes are equally likely processes. However, with an ensemble of molecules, the majority of molecules will be in the ground vibrational level Boltzmann distribution and Stokes scatter is the statistically more probable process.