Raman scattering is a consequence of quantized vibrations or rotations of molecules irradiated with monochromatic light. Some light is scattered at the same frequency (Rayleigh) and some light is scattered at different frequencies (Raman). The difference in frequency corresponds to the energy of vibrational transition. The Raman scattering can be divided into two parts, the Stokes line and the anti-stokes line. For the Stokes line the energy of the scattered radiation is less than the incident radiation, so there is a loss of energy and a longer wavelength results. For the anti-stokes line the energy of the scattered radiation is more than the incident radiation, so there is a gain of energy and a shorter wavelength results. There are two types of Raman spectroscopy: rotational Raman and vibrational Raman spectroscopy. A detailed study of the wave-numbers and wavelengths of the rotational and vibrational Raman lines (Stokes and anti-Stokes) are given in this article.
