Introduction to the Raman Effect

Lord Rayleigh's classical theory of Scattering, although could explain the blue colour of the sky, could not clear the skepticism about the colour of sea. C. V. Raman explained it with his historic discovery. Often called 'The optical analogue of Compton effect', Raman effect is one of the rare phenomena in Physics which can be explained fairly convincingly in both classical and quantum realms. Raman scattered light is obtained when a molecule absorbs light of certain frequency, gets excited to a different energy level, and re-emits a part of that light in a higher or lower frequency. It is classified as Stokes and Anti-Stokes scattering depending on whether the emitted light is of higher or lower frequency than the incident light. From the outset, Raman scattering may bear resemblance to Fluorescence, however, it differs in the fact that Raman scattered light is polarized. Wide-ranging applications of this effect includes: molecular fingerprinting, SERS in biomedical applications,in forensics, in crystallography, etc.

by Nabendu Sekhar mishra