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Raman scattering is an ideal technique that creates dispersed photons with distinct frequencies based on the rotational and vibration properties of the scattered molecules. Raman scattering is utilised to acknowledge the materials by physicists and chemists. In recent times, lasers are utilised to record the spectra whereas photographic plates and mercury lamps were utilised in calculating the spectra.
In the year 1928, Raman Scattering was uncovered by C.V Raman along with his famous student KS Krishnan. C.V Raman was awarded for his innovative discovery in the year 1930. It is demonstrated that one photon is scattered as Raman scattering is much less prevalent. Raman spectroscopy works well on Raman Scattering's principle.
What is Raman Scattering?
Raman scattering is demonstrated as an optical procedure where incoming light communicating with a sample creates the scattered light. This light is minimised in energy by modes of vibration of the specimen's chemical bond. The effect of Raman involves light scattering by molecules of solid, liquid or gases (Pilot et al. 2019).
The effect of Raman comprises the visibility of excessive spectra lines near incident light's wavelength. The lines of Raman in scattering light are weaker as compared to the light at actual wavelength.
Raman scattering is often considered weak because a single molecule within is rotationally and vibrationally excited before irradiation may rise to the lines of anti-strokes.
Figure 1: Raman Scattering
Raman Scattering has directional surface Plasmon that has amalgamated advantage of the resonance and spectroscopy and gives the capability to calculate chemical reactions that are monolayer sensitive and absorption. Raman scattering is generally utilised to study the low frequency, rotational and vibration molecule modes (Zhang et al. 2019).
The photons of scattering are inelastically scattered which demonstrates that the kinetic energy of the particles is increased or lost and is composed of anti-stokes and stokes portions.
Principles of Raman Spectroscopy
Monochromatic radiation is transferred through some samples that radiation may get scattered, absorbed or reflected. This is the main principle behind Raman spectroscopy as it works on the demonstration of Raman scattering (Bell et al. 2020). The wide number of photons are scattered at similar energy when light communicates with solid, liquid or gas.
Figure 2: Raman spectroscopy
The dispersed photons have a distinct frequency from the incident photon as the rotational and vibration properties vary. As opined by Guo et al. (2020), the variation consequences in the wavelength transformation which is acknowledged in the infrared-radiation spectroscopy.
Less number of the photons around 1 photon in millions may get dispersed at a distinct frequency in comparison to incident photons. The distinction between the dispersed and incident photon is termed as Raman shift.
Process of Raman Scattering
The process of Raman scattering is illustrated by quantum mechanics. It is when the photons communicate with the molecules that molecules may get advanced to the highest energy. The outcomes may be different from the state of higher energy (Lindquist et al. 2020). The probability of one such outcome is that the molecule may relax and comfort to the level of vibration energy that is distinct in comparison to the initiation state creating a photon of a different level of energy.
Classifications of Raman Scattering
Raman scattering generally emerges in mainly two ways such as stokes scattering and anti-stokes scattering. Stokes scattering happens when emitted radiation is of less frequency in comparison to the incident radiation (Xu et al. 2018). Anti-stokes scattering is the opposite of stokes scattering which demonstrated that emitted radiation is of higher frequency.
Figure 3: Classifications of Raman scattering
From the picture, it is demonstrated that the green arrow in the image shown represents incident radiation. The above picture represents that the levels of electronic energy are demonstrated by the labels ''n=". The Raman Effect helps in the demonstration of Raman spectroscopy and classifies an effective Raman scattering.
Applications of the Raman Effect
Raman spectroscopy is utilised in the industry in different applications which include crystallisation process, chemical synthesis, hydrogen reactions, Polymerisation reactions and many more.
However, the Raman Effect is utilised widely in different aspects. Raman amplification is utilised and based on the scattering of Raman where the photons of lower frequency are pumped to the regime of the higher frequency with huge amounts of energy. This procedure is highly applicable to telecommunications. In the optical phase, a super continuum is created utilising the spectra which consequence in smooth spectra as the initial spectra that are created instantly and later amplified to the higher energy (Song et al. 2020).
It is demonstrated from the study that Raman scattering is utilised in a planetary explosion and remote sensing. The Raman scattering is utilised to sense the minerals in mars. The application of the Raman Effect is obtained in multiple fields like "nanotechnology" to comprehend the structure of nanowires.
Raman scattering creates photons that are dispersed with different frequencies and rely on the source properties of molecules. The scattering is feasible to comprehend if the photon's behaviour is known to be subject to the light reflection. The transformed light wavelength is determined by the Raman Effect. There are seven visible colours in Raman scattering which are often familiar as "VIBGYOR" that are set from small to big wavelengths. From different experiments, it is seen that the blue colour is always scattered.
Q1. What is defined as Raman spectroscopy?
Raman spectroscopy is defined as a molecular technique of spectroscopy that uses the light interaction with matter to gain a particular insight that makes up features like FTR. The data provided by Raman spectroscopy consequences from the process of light scattering where IT depends on light absorption.
Q2. What is the utilisation of Raman spectroscopy?
Raman spectroscopy is utilised in calculating the scattering of light. It is basically used to acknowledge the low-frequency, rotational and vibration modes of the existing molecules.
Q3. What is the "degree of freedom"?
''Degree of freedom'' refers to the count of parameters that are in the determination of physical configuration. 3N is the formula to measure the ''degree of freedom'' in Raman scattering.
Q4. Which wave is utilised in Raman Spectroscopy?
UV wave is utilised for the screening method of Raman spectroscopy. Raman spectroscopy is based on the Raman Effect which utilises the beam scattering.
Bell, S. E., Charron, G., Cortés, E., Kneipp, J., de la Chapelle, M. L., Langer, J., ... & Schlücker, S. (2020). Towards reliable and quantitative surface‐enhanced Raman scattering (SERS): From key parameters to good analytical practice. Angewandte Chemie International Edition, 59(14), 5454-5462. Retrieved from: https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201908154
Guo, X., Li, J., Arabi, M., Wang, X., Wang, Y., & Chen, L. (2020). Molecular-imprinting-based surface-enhanced Raman scattering sensors. Acs Sensors, 5(3), 601-619. Retrieved from: https://www.nature.com
Lindquist, N. C., de Albuquerque, C. D. L., Sobral-Filho, R. G., Paci, I., & Brolo, A. G. (2019). High-speed imaging of surface-enhanced Raman scattering fluctuations from individual nanoparticles. Nature nanotechnology, 14(10), 981-987. Retrieved from: https://www.nature.com
Pilot, R., Signorini, R., Durante, C., Orian, L., Bhamidipati, M., & Fabris, L. (2019). A review on surface-enhanced Raman scattering. Biosensors, 9(2), 57. Retrieved from: https://www.mdpi.com
Song, C., Guo, S., Jin, S., Chen, L., & Jung, Y. M. (2020). Biomarkers determination based on surface-enhanced Raman scattering. Chemosensors, 8(4), 118. Retrieved from: https://www.mdpi.com
Xu, Z., He, Z., Song, Y., Fu, X., Rommel, M., Luo, X., ... & Fang, F. (2018). Topic review: Application of raman spectroscopy characterization in micro/nano-machining. Micromachines, 9(7), 361. Retrieved from: https://www.mdpi.com/
Zhang, X., Zhang, X., Luo, C., Liu, Z., Chen, Y., Dong, S., ... & Xiao, X. (2019). Volume‐enhanced raman scattering detection of viruses. Small, 15(11), 1805516. Retrieved from: https://onlinelibrary.wiley.com
Doitpoms, (2022). About Raman scattering. Retrieved from: https://www.doitpoms.ac.uk [Retrieved on: 11th June, 2022]