Rayleigh peak:

The positions of Raman lines are expressed in terms of Raman shift, ?defined as per the following equation.

which is

 While, s   and 0   are the wavenumbers of the source (or incident) radiation and the observed scattered lines respectively. It is obvious which the Raman shifts of the Stokes lines would be positive although for anti-Stokes lines, these would be negative.

We are sure in which you could remember that, firstly, the Stokes and anti-Stokes lines are equidistant from the Rayleigh line and secondly, the Stokes lines are much more intense as compared to the anti-Stokes lines. Now let us understand the mechanism of origin of the Raman lines, the purpose for the Stokes and anti-Stokes lines being equidistant from Rayleigh line and their associative intensities.

There are two theories of Raman effect. These are as follows:

• Quantum or particle theory
• Classical or wave theory