A New Radiation: C.V. Raman and the Dawn of Quantum Spectroscopy, Part I

In Part I of this series, we profile C.V. Raman’s discovery of the Raman Effect in 1928, which transformed physics and played a pivotal role in the development of quantum spectroscopy. By demonstrating that light scattering could lead to wavelength shifts, Raman provided experimental validation for quantum theory, laying the groundwork for modern spectroscopic techniques. His 1930 Nobel Prize-winning work continues to shape fields ranging from chemistry to biomedical science. This biography explores Raman’s journey from his early academic achievements to his trailblazing research, highlighting his lasting impact on quantum spectroscopy and its applications in contemporary science. In our 2-part series, we explore the life and discoveries of Raman in his pursuit of understanding “a new kind of radiation.”

Sir Chandrasekhara Venkata Raman (November 7, 1888–November 21, 1970), widely recognized as C.V. Raman, remains one of the most influential figures in physics, best known for his discovery of the Raman Effect—a phenomenon in light scattering that has significantly shaped modern analytical and spectroscopic science. Born in Tiruchirappalli, India, Raman demonstrated exceptional academic ability from an early age, laying the foundation for a career marked by innovation and dedication to scientific progress (1–4).

Portrait of C.V. Raman in 1930 (Public Domain Photo [3])

Raman's remarkable intellect shone brightly from an early age. He began his academic journey at A.V.N. College in Vizagapatam, where his father, Chandrasekaran Aiyar, served as a professor of mathematics and physics. Raman’s academic journey began with extraordinary promise. At just 13 years old, he earned a scholarship to Presidency College in Madras, India. By the age of 15, he had passed his B.A. examinations with top honors, earning gold medals in both English and Physics. Remarkably, he completed his M.A. at the age of 18, in January 1907, achieving the highest honors at that time (1,2,4).

Even before completing his master's degree, he made his first foray into scientific research. In 1906, he published a manuscript highlighting his brilliance titled “Unsymmetrical Diffraction-Bands Due to a Rectangular Aperture” in the London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science—better known as Philosophical Magazine (5). His early academic achievements foreshadowed his scientific passion and future potential as a uniquely gifted research physicist.

Despite his meek demeanor and humble visage, Raman’s genius was undeniable. On one occasion, a professor, mistaking his quiet presence for a lack of purpose, jokingly asked if his attendance at the college was a mistake, eliciting laughter from his classmates (2). However, Raman’s intellect soon made a lasting impression. His professors recognized his exceptional grasp of the curriculum, ultimately exempting him from attending science classes altogether, as he already had mastered the material being taught (2).

Raman’s professors were effusive in their praise, awarding him certificates of achievement filled with glowing remarks. Statements like “The best student I have had in 30 years,” “An unusual appreciation of English literature,” and “A facility in idiomatic expression” showcased a sample of the high regard in which he was held. These accolades underscored his remarkable mind and well-rounded talents even at such a young age (2).

Initially joining the Indian Finance Service (IFS), Raman worked as an Assistant Accountant General in Calcutta, where he discovered the Indian Association for the Cultivation of Science (IACS). This institution became central to his research in acoustics and optics, allowing him to conduct experiments during his free time. His first publication from IACS in 1907 marked the start of a prolific scientific career. His interest in acoustics was born of both his father’s and his love and skill at playing the violin (1–4).

In 1917, at age 29, Raman was appointed as the first Palit Professor of Physics at the University of Calcutta. Interestingly, he was not the initial choice for the position; it had first been offered to J. C. Bose, who declined. At first, Raman was reluctant to accept the role, as the offered salary of 600 rupees (approximately $4700 of today’s U.S. dollars) was only about half of what he was earning as a bank officer.

At this pivotal moment, history owes a great debt of gratitude to Raman’s 25-year-old wife, Lokasundari Ammal ​ (1892–1980), whom he had married in 1907, who played a key role in shaping history. She encouraged him to accept the professorship, reassuring him not to let financial concerns deter him. Her support and vision for his potential impact on science ultimately influenced his decision, setting him on the path to his remarkable discoveries (4).

It was at the University of Calcutta that he began to explore light scattering, leading to the discovery of the Raman Effect on February 28, 1928. Using a self-designed spectrograph, Raman and his student, K. S. Krishnan, observed a change in the wavelength of light passing through a transparent medium. This uniquely visionary work earned Raman the 1930 Nobel Prize in Physics (4).

Raman’s curiosity extended beyond the laboratory. During his first trip to Europe, he challenged the prevailing explanation for the blue color of the Mediterranean Sea, offering an alternative view on light scattering. He also established platforms for scientific discourse, founding the Indian Journal of Physics in 1926. In 1933, he moved to Bangalore to become the first Indian director of the Indian Institute of Science (IISc), where he mentored future scientific leaders like crystallographer G. N. Ramachandran and founded the Indian Academy of Sciences (1–3).

Beyond academia, Raman co-founded the Travancore Chemical and Manufacturing in 1943, one of India’s first chemical manufacturing companies. After retiring from IISc in 1948, he established the Raman Research Institute in Bangalore, remaining active in research until his death in 1970 (1–3).

Raman’s legacy is celebrated annually on February 28 as National Science Day in India, commemorating his discovery of the Raman Effect. His contributions to science and the institutions he founded continue to inform and inspire generations of researchers. Raman’s story is one of perseverance, intellectual rigor, tenacity, and a lasting impact on the global scientific community.

Foundational Research History

The following Research papers were cited for Raman’s nomination to the Royal Society of London in 1921 (6). From these papers, where PDF versions are available in the reference links, the reader may observe the depth of understanding of Raman for the physical laws of vibration and motion—fundamental understanding that served him well in the discovery of the Raman Effect. His scientific research work up to 1928 was in acoustics, astronomy, and optics (2,4). These manuscript titles and corresponding references are as follows:

• Experimental Investigations on the Maintenance of Vibration (7)
• The Dynamical Theory of the Motion of Bowed Strings (8)
• On the Mechanical Theory of the Vibrations of Bowed Strings and of Musical Instruments of the Violin Family: With Experimental Verification of the Results (9)
• On Kaufmann’s Theory of the Pianoforte Hammer (10)
• Photometric Measurement of the Obliquity Factor of Diffraction (11)
• On The Diffraction-Figures due to an Elliptic Aperture (12)
• The Colours of Mixed Plates, Parts 1 and 2 (13,14)

The Raman Effect

The history of Raman spectroscopy begins with the discovery of the "scattering effect" by C.V. Raman and Kariamanikam Srinivasa (K. S.) Krishnanin (1898–1961) in 1928. The Raman Scattering Effect was named after Raman despite the fact that the Russian physicists Grigorii Samuilovich Landsberg (1890–1957) and Leonid Isaakovich Mandelstam (1879–1944) made the same fundamental discovery at the same time (4).

The discovery of the Compton effect in 1923 laid the groundwork for understanding the Raman scattering effect by establishing the concept of wavelength shifts resulting from interactions between light and matter. Albert Einstein’s 1905 hypothesis of light quanta, which suggested that light could behave as discrete packets of energy, faced significant skepticism from physicists of the time. It was not until Arthur Holly Compton demonstrated the change in the wavelength of X-rays after colliding with electrons in a substance—described as a "billiard-ball collision process"—that the quantum nature of light gained broader acceptance.

Building on the understanding of light-matter interactions established by Compton, Raman and Krishnan discovered a similar phenomenon involving the scattering of visible light in 1928. Unlike the Compton effect, which involved high-energy X-rays, the Raman Effect dealt with lower energy monochromatic visible light and revealed that scattered light also undergoes a shift in wavelength, depending on its interaction with the specific molecular structure of the medium.

The Raman Effect provided further evidence supporting the quantum theory of light and was recognized for its broad implications. Renowned physicist Robert Williams Wood praised Raman’s discovery as one of the strongest confirmations of the quantum nature of light, emphasizing its significance in advancing the understanding of optical phenomena (4). Together, these discoveries demonstrated the universal applicability of quantum principles to both high-energy and visible light interactions, cementing the role of quantum mechanics in the study of light.

The challenges of observing the Raman Effect were significant in the mid-1920s. Before the advent of lasers, the brightest available light sources—sunlight and quartz mercury arc lamps—were used. These light sources were filtered to specific wavelengths, primarily in the green region of 435.6 nanometers, to excite the scattering effect, initially referred to as "a new radiation." Early experiments employed glass photographic plates to capture spectra, showing emission lines shifted to longer wavelengths (lower energy) compared to the source light (15).

The intensity of Raman scattering is extremely low, with scattered light constituting only 1 part in 1 million to 1 part in 100 million (10⁻⁶ to 10⁻⁸ ) of the source light intensity. As a result, early experiments required long exposure times, ranging from several hours to nearly 200 hours, to capture the spectral bands on photographic plates. Benzene was one of the first substances analyzed, and a library of over 60 spectra for liquids and gases was compiled by Raman, showcasing this newly discovered phenomenon (4). Raman's clear demonstration and detailed explanation of the scattering phenomenon earned him sole recognition for the 1930 Nobel Prize in Physics.

Modern Raman spectrometers utilize laser excitation, which provides a concentrated photon flux in a short time. Combined with advanced filters, sensitive detectors, and quiet electronics, they allow real-time spectral acquisition and imaging. Current instruments display Raman shift (in cm⁻¹) versus intensity, offering high precision and efficiency compared to the labor-intensive methods of the past. The advancements in laser technology and detection systems have revolutionized Raman spectroscopy, enabling detailed and rapid composition analysis for many applications (15).

References

(1) Indian Academy of Sciences. Chandrasekhara Venkata Raman–A Memoir. Website: www.ias.ac.in. A. Jayaraman. Available at: https://www.ias.ac.in/public/Resources/Other_Publications/e-Publications/003/Chandrasekhara_Venkata_Raman.pdf (accessed 2025-02-07).

(2) Ramaseshan, S. C. V. Raman Memorial Lecture, Indian Institute of Science, Bangalore, March 3, 1978. Available at: http://dspace.rri.res.in/bitstream/2289/1508/1/1978Ramaseshan_CVRamanLecture.pdf (accessed 2025-02-07).

(3) C. V. Raman Wikipedia Home Page. Available at: https://en.wikipedia.org/wiki/C._V._Raman (accessed 2025-02-07).

(4) Singh, R. C. V. Raman and the Discovery of the Raman Effect. Phys. Perspect. 2002, 4 (6), 399–420. DOI: 10.1007/s000160200002. Available at: https://www.researchgate.net/profile/Rajinder-Singh-33/publication/226927241_C_V_Raman_and_the_Discovery_of_the_Raman_Effect/links/0c96052c8230b8ae4f000000/C-V-Raman-and-the-Discovery-of-the-Raman-Effect.pdf (accessed 2025-02-07).

(5) Raman, C. V. Unsymmetrical Diffraction Bands Due to a Rectangular Aperture. Philos. Mag. 1906, 12 (71), 494–498. DOI: 10.1080/14786440609463564

(6) Singh, R.; Riess, F. The Nobel Laureate Sir Chandrasekhara Venkata Raman FRS and His Contacts with the British Scientific Community in a Social and Political Context. Notes Rec. R. Soc. Lond. 2004, 58 (1), 47–64. DOI: 10.1098/rsnr.2003.0224

(7) Raman, C. V. Experimental Investigations on the Maintenance of Vibrations. Bull. Indian Assoc. Cultiv. Sci. 1912, 6, 1–40. Available at: https://repository.ias.ac.in/69874/1/69874.pdf (accessed 2025-02-07).

(8) Raman, C. V. The Dynamical Theory of the Motion of Bowed Strings. Bull. Indian Assoc. Cultiv. Sci. 1914, 11, 43–52. Available at: https://repository.ias.ac.in/69862/1/69862.pdf (accessed 2025-02-07).

(9) Raman, C. V. On the Mechanical Theory of the Vibrations of Bowed Strings and of Musical Instruments of the Violin Family: With Experimental Verification of the Results (No. 15). Indian Assoc. Cultiv. Sci., 1918. Available at: https://core.ac.uk/reader/291564080 (accessed 2025-02-07).

(10) Raman, C. V.; Banerji, B. On Kaufmann's Theory of the Impact of the Pianoforte Hammer. Proc. R. Soc. Lond. A 1920, 97 (682), 99–110. Available at: https://repository.ias.ac.in/69875/1/69875.pdf (accessed 2025-02-07).

(11) Raman, C. V. The Photometric Measurement of the Obliquity Factor of Diffraction. Nature 1909, 82 (2090), 69. Available at: https://www.nature.com/articles/082069b0#preview (accessed 2025-02-07).

(12) Raman, C. V. On the Diffraction-Figures Due to an Elliptic Aperture. Phys. Rev. 1919, 13 (4), 259. DOI: 10.1103/PhysRev.13.259

(13) Raman, C. V. On the Colours of Mixed Plates. Part I. Philos. Mag. 1921, 41 (243), 338–347. Available at https://repository.ias.ac.in/76660/ (accessed 2025-02-07).

(14) Raman, C. V. On the Colours of Mixed Plates. Part II. Philos. Mag. 1921, 41 (246), 860–871. Available at: https://repository.ias.ac.in/76661/ (accessed 2025-02-07).

(15) Workman, J. Concise Handbook of Analytical Spectroscopy, The: Theory, Applications, and Reference Materials (In 5 Volumes); World Scientific: 2016; pp 6–9. DOI: 10.1142/8800. Available at: https://worldscientific.com/worldscibooks/10.1142/8800 (accessed 2025-02-07).

About the Author

Jerome Workman, Jr. serves on the Editorial Advisory Board of Spectroscopy and is the Executive Editor for LCGC and Spectroscopy. He is the co-host of the Analytically Speaking podcast and has published multiple reference text volumes, including the three-volume Academic Press Handbook of Organic Compounds, the five-volume The Concise Handbook of Analytical Spectroscopy, the 2nd edition of Practical Guide and Spectral Atlas for Interpretive Near-Infrared Spectroscopy, the 2nd edition of Chemometrics in Spectroscopy, and the 4th edition of The Handbook of Near-Infrared Analysis. Author contact: JWorkman@MJHlifesciences.com●