RAM: Raman Effect

The Raman Effect is a shift of wavelength that occurs when light is scattered by molecules. Classically, it comes from sum and difference frequencies between a molecule with electric susceptibility at one characteristic frequency driven by pump light at another frequency -- the molecular polarization response is the product of these two functions, and by a trig identity the product can be rewritten in two terms, at sum and difference frequencies.

In this experiment, the scattering of 532nm laser light by sulphur powder, benzene and carbon tetrachloride is studied, and "satellite" lines are observed due to the exchange of energy between the scattered photons and the internal vibrational and rotational states of the scattering molecules. The frequencies of these lines give information on the structure of the scattering molecule. Sir Chandrasekhara Venkata Raman won the Nobel Prize in Physics in 1930.

Write-Up in PDF Format or Microsoft Word Format.

(The experiment is currently located in MP248. There has been a substantial revision of the apparatus, and a new write-up revision: September 2021.)

Additional resources:

Example spectrum of sulphur.

Sample spectrum from sulphur powder, in new laser-pumped setup August 2020.