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Raman Effect

Raman Effect 


Raman scattering or the Raman effect  is the inelastic scattering of a photon by molecules which are excited to higher energy levels. The effect was discovered in 1928 by C. V. Raman and his student K. S. Krishnan in liquids,and independently by Grigory Landsberg and Leonid Mandelstam in crystals.The effect had been predicted theoretically by Adolf Smekal in 1923.
When photons are scattered by a material, most of them are elastically scattered (Rayleigh scattering), such that the scattered photons have the same energy (frequency and wavelength) as the incident photons but different direction. However, a small fraction of the scattered photons (approximately 1 in 10 million) are scattered inelastically, with the scattered photons having an energy different from, and usually lower than, those of the incident photons—these are Raman scattered photons.
Because of conservation of energy, the material either gains or loses energy in the process. Typically this is vibrational energy and the incident photons are of visible light, although rotational energy (if gas samples are used) and electronic energy levels (if an X-ray source is used) may also be probed. The Raman effect forms the basis for Raman spectroscopy which is used by chemists and physicists to gain information about materials.


Explanation
Sometimes a rainbow appears and delights our eyes. We see in it shades of red, orange, yellow, green, blue, indigo and violet.
The white ray of the sun includes all these colors. When a beam of sunlight is passed through a glass prism a patch of these *color- bands are seen. This is called the spectrum.
The Spectro- meter is an apparatus used to study the spectrum. Spectral lines in it are characteristic of the light passing through the prism. A beam of light that causes a single spectral line is said to be monochromatic.
When a beam of monochromatic light passes through a transparent substance (a substance which allows light to pass through it), the beam is scattered.
On February 28, 1928, he observed two low intensity spectral line corresponding to the incident mono- chromatic light.
It was clear that though the incident light was monochromatic, the scattered light due to it, was not monochromatic.
Thus Raman's experiments discovered a phenomenon which was lying hidden in nature.
The 16th of March 1928 is a memorable day in the history of science. On that day a meeting was held under the joint auspices of the South Indian Science Association and the Science Club of Central College, Bangalore; Raman was the Chief Guest.
He announced the new phenomenon discovered by him to the world. He also acknowledged with affection the assistance given by K.S. Krishnan and Venkateshwaran, who were his students.
The phenomenon attracted the attention of research workers all over the world. It became famous as the 'Raman Effect'. The spectral lines in the scattered light were known as 'Raman Lines'.
Definition:-
Raman effect, change in the wavelength of light that occurs when a light beam is deflected by molecules. When a beam of light traverses a dust-free, transparent sample of a chemical compound, a small fraction of the light emerges in directions other than that of the incident (incoming) beam. Most of this scattered light is of unchanged wavelength. A small part, however, has wavelengths different from that of the incident light; its presence is a result of the Raman effect.
Inception of Raman effect makes the advancement in different fields pharmaceutical industries, quality analysis of materials, drug analysis, baggage checking, geology, archaeology, forensic works, etc.
  • In Medicinal tablets, Raman effect will show the chemical components distribution, purity of raw material.
  • In cosmetics, It will clearly shows the depth of act of chemical material you apply on your skin.
  • It is very useful in finding the quality of diamond materials and gem stones.
  • In detecting bombs, drugs, hidden substances, hazardous chemicals and gases.
  • It is also useful in finding the composition of cancer tumors.
  • It has been used by NASA in MARS mission to research.
  • It is also used in archeological field to find out the material and its details.



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