Raman Spectrum is typically a chemical fingerprint for a particular molecule or material, and it can be used to quickly identify the material without any consume of the samples.
How does Raman Spectroscopy work?
Raman effect is first discovered by C.V. Raman and K.S Krishan in 1928. When a sample exposes monochromatic light, the sample absorbs the light, visual portion of light gets transmitted to the sample. However, a minor part of the light is scattered by the sample in all direction. Incident light has a particular frequency, if scattering light has frequency same as incident light, the scattering is called Rayleigh scattering. It has been observed that about 1% of total scatter intensity occurs frequency different from incident frequency, this is called Raman scattering. Raman scattering can be called a two photon process, an electron has different vibrational levels, they are defined by different specific energy differences.
When an incident molecular light interacts with an electron in the sample, an electron absorbs energy from an incident photon. It strikes the state of virtual energy, the energy transform is given by a formula. the electron falls back to energy level by losing energy. If energy loss equals the energy of the incident photon. An electron falls back to an initial level, and if this process emits another photon, since the energy loss equal value same frequency of the incident photon, as the frequency is same, Rayleigh scattering occurs. However, sometimes electron loss energy from virtual state to fall back to different vibration level. In this case, energy loss by the electron is different, and the energy absorbed from incident photon, as a result, photon emitted, the photon has energy different from incident photon, it's possible when the frequency of emitted photon is different from the frequency of incident photon, this gives right to Raman scattering, depends on final energy of electron or final vibrational of electron, Raman scattering can be separated into two, stock lines and anti-stocks lines.
If the frequency of scattering photon less than the frequency of the incident photon, stocks lines is observed on Raman spectra. It happens when an electron absorbs energy, Similarly, If frequency If scattering photon greater than the frequency of the incident photon, anti-stocks lines is observed, this means the energy released by the electron. Raman spectra give a molecular fingerprint, different molecules have different Raman spectra, By studying spectra, one can identify rotational levels and, it helps to perform analysis of qualitative, similarly, the intensity of particular Raman lines help determine the concentration of molecule in a sample, In this manner, quantitive analysis can be done. Thus Raman spectroscopy can be used as both qualitative and quantitative analysis tool.
Information provided by Raman Spectroscopy
Chemical structure and identity
Phase and polymorphism
Contamination and impurity
Advantage for use Raman Spectroscopy
No need to touch the samples
Quick test, you could know the result in 1 to 10 seconds.
No need to sample pretreatment ( except trace detection）
Application of Raman Spectroscopy
Raman can be used to analyze many different kinds of samples, in general it is suitable for analyzing:
Solids, powders, liquids, gels, slurries and gases
Inorganic, organic and biological materials
Pure chemicals, mixtures and solutions
Metallic oxides and corrosion
It is good to used for:
Art and archaeology – characterization of pigments, ceramics and gemstones
Carbon materials – structure and purity of nano-tubes, defect/disorder characterization
Chemistry – structure, purity, and reaction monitoring
Geology – mineral identification and distribution, fluid inclusions and phase transitions
Life sciences – single cells and tissue, drug interactions, disease diagnosis
Pharmaceutics – content uniformity and component distribution
Semiconductors – purity, alloy composition, intrinsic stress/strain microscope.
Public Safety – drugs, chemicals, explosives, narcotics