Raman Effect

Raman Scattering Introduction

Indian Physician, C.V. Raman had discovered the non-linear scattering of photons which is named as Raman Effect or Raman Scattering. C.V. Raman founded the higher level excitement in molecules or photons in the year of 1928, and this inelastic scattering is called Raman effect. Besides, the Nobel Prize was awarded to him in 1930 for his achievements in Physics. Raman scattering generates photons that are scattered with various frequencies depending on the source and rotational and vibrational properties of scattered photons or molecules. In addition, Raman scattering was very useful for other researches such as quantum theory and it was appreciated and recognised by other scientists also. In an earlier time, photographic plates and mercury lamps were used to study the spectrum of photons and Raman spectroscopy was helpful in studies of various materials by physicists and chemists. Nowadays, the laser has replaced the photographic plates and mercury lamps.

What Is Raman Scattering?

Raman scattering becomes easy to understand if you know the behaviour of photons subjecting the reflection of light. When a light beam is deflected through molecules, the wavelength of light is changed. The changed wavelength of light is known as the Raman effect. Well, it is infrequent that any photon or light turns its wavelength. When the energy level is high, excited molecules may scatter the photons. Mostly the photons are scattered elastically, but rarely a few photons change its wavelength inelastically. In this process, the incident particle's kinetic energy can be increased or lost.

You can compare the inelastic scattering with an inelastic collision as the concept of both theories are the same. According to the inelastic collision, complete microscopic kinetic energy is not conserved. While inelastic collision, kinetic energy is transferred, but scattering is still inelastic such as Compton scattering.

Degrees of Freedom

To determine the physical system's parameter, many parameters should be counted individually. So, the DOF (degree of setting) is the count of such independent parameters that are included in the physical configuration determination. Note down the following formula as DOF in Raman effect.

DF (degree of freedom) =n−1

Where,

DF=DOF= degree of freedom

N= number of samples or atoms (given)

For the Raman effect, the DOF (considered for any chemical compound) is 3N. Here N is the count of atoms that participated in the given chemical compound. It would help if you found the movement of the molecules as a whole when you deal with particles in Raman scattering. So, 3N DOF is partitioned into three parts: vibrational, rotational and translational motion. The direction of molecules also follows the same manner corresponding degree of freedom to molecules rotation in the direction of x, y, and z axes corresponding.

What Is Raman Spectroscopy

Raman spectroscopy is a device that employs Raman scattering and is widely used to study the different entities of molecules such as rotational, vibrational and low-frequency modes. Indian physician C.V. Raman made Raman spectroscopy in 1928. Well, it has made many changes in information observation in chemistry. Raman spectroscopy employing Raman effect had involved many essential applications of Raman effect.  

Raman spectroscopy was discovered by C.V.Raman in the year 1928 to study the vibrational, rotational and low-frequency modes of the molecules. It finds application mainly in chemistry to get the information related to fingerprints. In addition, it is also used in many applications in cosmetic products industry, pharmaceutical agents, mineralogy, geology, analysing semiconductors and daily life applications.

Raman Spectroscopy Principle

When the monochromatic radiation is traversed on the given sample in such manner that radiation may get scattered, absorbed, or reflected. The process of such radiation through monochromatic radiation is the Raman spectroscopy principle. The frequency of photons may vary depending on the difference in rotational and vibrational properties of the photons. The contrast of photons frequency can be defined as IR spectra that show the wavelength change.

Raman shift takes place when there is a difference between a scattered photon and incident photon. If the energy of scattered photons is less than the incident photon's energy, it is called the Stokes scattering. Sometimes, the strength of scattered photons is more than the incident photon; such type of scattering is identified as anti-stokes scattering.

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Types of Raman Spectroscopy

Raman effect can be implemented in many ways, and it is beneficial for various industries as well. So, types of Raman spectroscopy are there to gain the best utilisation of the Raman effect. 

Four Kinds of Raman Spectroscopy 

Resonance Raman Spectroscopy (RRS)

Micro-Raman Spectroscopy

Surface-enhanced Raman Spectroscopy (SERS)

Non-linear Raman Spectroscopic Techniques

Application of Raman Effect

Supercontinuum Generation

Supercontinuum is created in optics that forms the smooth spectra. Initially, ranges are formed spontaneously and then after it is amplified the higher-level energy.

Raman Amplification

Raman amplification is based on the Raman scattering, which relies on the frequency of photons.  In Raman scattering, photons with lower frequency are pumped to the regime of higher spectrum added with surplus energy. Generally, Raman amplification is applied in telecommunication.

In nanotechnology, Raman spectroscopy is used to study the nanowires' structure because this device is based on the Raman effect that can be implemented in different applications. Researchers use it to analyse the DNAs that have low-frequency and structure of the protein in the medical and biology field. The application of this device is not limited and has a vast area of usage. In chemistry, it is used to understand the molecules bond and structure in the given compound.

FAQ (Frequently Asked Questions)

Q1. Explain Is Raman Spectrometer?

Raman spectrometer is a device consisting of one or more light sources that are single coloured and filters and lenses that are used to focus the light. Lens and filters also differentiate the scattered and reflected light. Take the example of the prism. The prism splits the light on the detectors that detect light, especially those that are weak. Information of light is monitored and analysed on the monitor where the spectrum is obtained.

Q2. What Is Raman Spectra?

Scattered photon's wavelength must be converted into the wavenumber to analyse the Raman scattering. Wavenumbers are represented on an x-y plane where x-axes are for wavenumbers and y-axes is for Raman intensity. So, the Raman spectra are the difference between the wavenumbers and Raman intensity.