Raman Scattering: Overview, Questions, Preparation

C. V. Raman discovered the concept of the Raman effect in the year 1928. In the year 1930, he was awarded the Nobel Prize in the field of Physics. The concept of Raman scattering was similar to the Rayleigh scattering because both concepts are dependent on the polarizability of the molecules.

Raman scattering is defined as the scattering of the photon molecules having high energy levels. Raman scattering is also known as the Raman effect. The photons in Raman are scattered randomly, which means that the molecules’ kinetic energy is composed of Stokes and anti-stokes portions and can be either decreased or increased.

Degrees of Freedom

As the name clearly states, the degree of freedom states that the physical system’s configuration determines the number of free variables. The formula of the degree of freedom is written below:

DF = n – 1

Here, DF means the degree of freedom,

And n is the number of samples.

In the Raman scattering, the degree of freedom is 3 N, and N is the number of atoms or samples. The reason behind the 3N degree of freedom is because the atoms move in x, y, and z-direction freely. Each atom possesses the motion of translational, rotational, and vibrational simultaneously.

In 1928, C. V. Raman discovered Raman Spectroscopy’s concept to study the modes of molecules that include vibrational, rotational, and translational molecules. It is widely used in the field of chemistry to find out the information related to fingerprints. There are mainly four types of Raman Spectroscopy which are listed below:

1. Resonance Raman Spectroscopy
2. Micro – Raman Spectroscopy
3. Surface-enhanced Raman Spectroscopy
4. Non – linear Raman Spectroscopy

The principle of Raman Spectroscopy is evident and simple. It deals with the samples’ monochromatic radiations to get a clear picture of the know-how of radiations that may reflect, absorb, and scatter.

The scattered photons and incident photons both have different frequencies and different vibrational and rotational properties.

Raman shift is the difference between the scattered photon and the incident photon. They are used to determine the Stokes and anti-stokes scattering. When the energy possessed by the scattered photons is more than that of incident photons, then it is called anti-stokes scattering and vice versa.

The chapter ‘Light Sources’ holds a weightage of 8 marks. It includes four questions in total, three objective type questions of 1 mark each, one long question of 5 marks. Thus, making a total of 8 marks.

Example 1) Write the types of Raman Spectroscopy.

Answer – The Types of Raman Spectroscopy are as follows:

1. Resonance Raman Spectroscopy
2. Micro – Raman Spectroscopy
3. Surface-enhanced Raman Spectroscopy
4. Non – linear Raman Spectroscopy

Example 2) Write the formula of Raman’s scattering to calculate the DF.

Answer – The formula of Raman’s Scattering is 3N

Example 3) Write one application of the Raman Effect.

Answer – Raman Effect is used for the amplification process.

Q: What do you mean by Degree of Freedom?

Q: What is the formula of the degree of freedom?

Q: What is ‘n’ in DF formula?

Q: What is Raman Spectra?

Q: Why is Raman Spectroscopy used?