CV Raman Saw New Lines of Light in a Calcutta Laboratory on 28 February 1928, and Two Years Later Became the First Asian to Win a Science Nobel

The Raman effect is a small change in the colour of light after it scatters off molecules. CV Raman first saw it as sharp new lines in a spectroscope, an instrument that spreads light into its colours, on 28 February 1928 at the Indian Association for the Cultivation of Science (IACS), 210 Bowbazar Street, Calcutta. A Nobel Prize in Physics followed in 1930, and the Lindau Nobel Laureate Meetings foundation describes him as the first Asian scientist to win a Nobel Prize in science.

Historians still argue over two parts of the story. One is how much credit belongs to his student KS Krishnan. The other is how to treat two Soviet physicists who saw the same lines in a crystal in Moscow at almost the same time.

What the Raman effect is, in plain words

Shine a beam through a clear liquid and the molecules scatter some of it sideways, which is why you can see the beam from the side. Most of that scattered light keeps the colour it started with. The Nobel Foundation’s summary says Raman found in 1928 that a small portion acquires other wavelengths, because some of the energy of the incoming photons, the packets of light, can pass to a molecule.

H Pleijel, chairman of the Nobel Committee for Physics, described the test in his presentation speech on 10 December 1930. A sample was lit with a single line of a mercury lamp and the scattered light watched in a spectrograph, which records each wavelength as a line. New sharp lines appeared on either side of the original, and when the mercury line was changed the new lines moved with it, keeping the same gap. The gaps match the vibration frequencies of the molecule itself, Pleijel explained, so they differ from one substance to another.

A blue sea and six years of scattering

Raman was born at Tiruchirappalli on 7 November 1888. A master’s degree from Presidency College, Madras, came in 1907. The Nobel Foundation’s biography says a scientific career did not then look like the best prospect, so he joined the Indian Finance Department that year. The job took most of his time, but he found chances to do experiments in the IACS laboratory.

Mahendralal Sircar founded the IACS, and the American Institute of Physics gives its founding date as 29 July 1876. According to the physicist Arnab Rai Choudhuri, Raman noticed its signboard from a tram on his way to work, walked in, and was welcomed by Sircar’s son. By 1917 he had accepted the newly endowed Palit Chair of Physics at Calcutta University, and in 1919 he became honorary secretary of the IACS.

The sea comes in 1921. A voyage to Europe that summer gave him his first chance to see “the wonderful blue opalescence of the Mediterranean Sea”, he wrote in his Nobel lecture. Sunlight scattering off the water’s molecules seemed a likely cause of the colour. Experiments to test that began when he was back in Calcutta in September 1921.

For the next six years the lab studied scattering in gases, liquids and crystals, and the lecture names nine collaborators for that period. It also describes the puzzle that led to the discovery: besides ordinary scattering there was a much fainter glow of a different colour. KR Ramanathan first observed it in April 1923, Raman says, and it did not weaken after repeated distillation in vacuum, so an impurity was ruled out. Krishnan found it in many other liquids in 1924. The paper by Ramanathan and Krishnan called it “feeble fluorescence”. Raman said in 1928 that he suspected a new kind of radiation but held back, because few liquids seemed to show it and it was assumed to be unpolarised, like fluorescence.

Sunlight, a seven-inch lens and a mercury lamp

The next steps come from the Nobel lecture and from Raman’s address of 16 March 1928 to the South Indian Science Association in Bangalore. S Venkateswaran took the problem up again in January 1928, and according to the lecture reported that sunlight scattered by purified glycerine came out “a brilliant green instead of the usual blue”. Early that year, Raman said in Bangalore, he conceived the idea that the effect was some kind of optical analogue of the X-ray scattering found by Compton, in which the scattered X-rays come out with a changed wavelength. Then came a fresh round of experiments with Krishnan.

Sunlight served for the first tests. A heliostat, a mirror that follows the sun, sent it through a seven-inch telescope lens and a short-focus lens, which squeezed it into a bright pencil. The beam passed through a blue-violet filter and then through a liquid in an evacuated glass bulb. A green filter of the complementary colour was held either in the incoming beam, where it blocked everything, or between the bulb and the observer’s eye. With the filter in the second position the track of light inside the liquid stayed visible. About 80 liquids, Raman said, all showed it, and the light was nearly as strongly polarised as ordinary scattering, which fluorescence usually is not.

Both men signed a letter to Nature from 210 Bowbazar Street, dated 16 February, which appeared on 31 March 1928 as “A New Type of Secondary Radiation”. The Russian physicist IL Fabelinskii notes in a 1998 history that it described the sunlight and crossed-filter work and could not show lines.

The lines came on 28 February. Raman’s address describes switching to a quartz mercury lamp with a filter that cut every visible mercury line longer in wavelength than the indigo line at 4,358 angstrom units (about 436 nanometres). The light went through a dust-free liquid and the scattered light was viewed through a direct-vision spectroscope. Two or more sharp bright lines showed up in the blue and green that the lamp itself did not produce. “The line spectrum of the new radiation was first seen on the 28th February 1928,” Raman said in Bangalore, adding that the observation was made public the next day. Bhagavantam, a collaborator, recalled in 1978 that a Calcutta daily carried the announcement on 29 February.

The lecture says the first photographs came from the smallest portable quartz spectrograph made by the firm Hilger, and that Krishnan, with a larger one, first definitely established lines shifted toward the violet end. A second Nature paper by the two men is dated 8 March and was published on 21 April 1928.

Who gets the credit in Calcutta

Raman’s Bangalore address closes with thanks to Krishnan: “I owe much to the valuable co-operation in this research of Mr K S Krishnan.” Krishnan “very materially assisted” him, the Nobel lecture adds. Most of the papers in the discovery series carry both names, Choudhuri notes.

Whether Krishnan has received enough credit is “another more serious dispute”, in Choudhuri’s words. He quotes Krishnan’s diary, as published by DCV Mallik in 2000. An entry for 9 February 1928 has Raman, discussing the problem with Krishnan and Venkateswaran, saying the phenomenon “should be called the Raman-Krishnan-Effect”. The diary is found torn, Choudhuri adds, ending mid-sentence in the entry for 28 February. The Nobel Prize went to Raman alone, as a full share.

A second question is 1923. Writing in Nature in January 1929, Raman said changed wavelengths had been established in Calcutta as far back as 1923. Fabelinskii disagrees. The work of Ramanathan and Krishnan shows luminescence, he says, and Krishnan himself understood he was seeing fluorescence, not the effect. Raman’s Nobel lecture is more careful than the 1929 letter: it calls Ramanathan’s finding the first observation of a puzzling phenomenon, and says the first sign of its true nature came “from a different quarter”, the glycerine result.

A week earlier in Moscow

Leonid Mandelstam and Grigory Landsberg, at Moscow State University, were looking for something else in quartz: fine structure in light scattered by the heat vibrations of the crystal. Fabelinskii worked 20 years in Landsberg’s laboratory. He quotes Mandelstam’s reply to the physicist Orest Khvolson that they first noticed the new lines on 21 February 1928, and says Landsberg dated a 15-hour negative showing them 23 to 24 February.

Calcutta reached print first, on 31 March and 21 April. The Moscow paper was submitted to the journal Naturwissenschaften on 6 May and issued on 13 July. A relative of Mandelstam was arrested on 15 March 1928, Fabelinskii writes, and the time spent getting the man released explains the delay. By his account the Moscow paper gave the correct quantum explanation from the start, while Raman and Krishnan at first thought the shifted lines sat in the same place for every substance and read the violet-side lines as evidence of “negative absorption”.

Contemporaries treated the two finds as independent. Max Born, writing after a Soviet physics congress in August 1928, said the Moscow discovery was made independently of the Indians and nearly simultaneously, Fabelinskii reports. Raman wrote in Nature in January 1929 that the Russians made their first communication after the Nature papers of 31 March and 21 April, which matches the dates above. It would be fair to call the phenomenon the effect of Raman, Mandelstam and Landsberg, says Fabelinskii. Smekal had predicted such extra frequencies in 1923, he notes, and Kramers and Heisenberg published the theory in 1925.

The 1930 prize and the booked passage

The Nobel Foundation’s nomination archive lists ten nominations for Raman in 1930, including from Niels Bohr, Louis de Broglie, Ernest Rutherford, Jean Perrin and Charles Wilson. One of the ten, from Khvolson, named Landsberg and Mandelstam alongside him. Nikolay Papaleksi nominated Mandelstam alone. That makes one nomination for Landsberg and two for Mandelstam.

The prize went to Raman, a full share, “for his work on the scattering of light and for the discovery of the effect named after him”. His lecture, “The molecular scattering of light”, followed on 11 December 1930. The Royal Society had elected him a Fellow in 1924, and the knighthood came in 1929. Recent prizes in the same field are explained in what the 33 science Nobel Prizes of 2016 to 2026 were for.

Fabelinskii calls the committee’s decision a mistake, since all three could have shared the prize. Rumours that the committee disliked the Soviet system do not hold up, in his view, and he points instead to reasons raised by the physicist VL Ginzburg. Soviet physicists entitled to nominate mostly did not put forward Landsberg and Mandelstam, and foreign physicists who knew their work, Rutherford among them, proposed Raman alone. Bhagavantam’s 1978 recollection, which Fabelinskii quotes, is that two months before the award was announced Raman had booked his steamer passage to be in time for the ceremony in Stockholm.

What the spectra turned out to be good for

Molecular vibrations lie in the infrared, Pleijel told the ceremony, far from the range where photographic plates of 1930 were sensitive. With the Raman lines, he said, that spectrum is moved up to a range where plates work and can be measured exactly.

Fabelinskii counts 70 publications on the effect in 1928 and about 200 by the end of 1929, and 1,800 papers by around 1939 covering the spectra of 2,500 compounds. High-power laser sources later allowed new phenomena in combination scattering to be found, he adds. The Nobel Foundation says the phenomenon is used to analyse different types of material.

On Mars, NASA’s Perseverance rover carries SHERLOC, an instrument named for Raman and luminescence spectroscopy. A cover problem had left its Raman capability offline, NASA said in an update dated 5 March 2024.

Bangalore, a laboratory of his own, and the last years

Next came the Indian Institute of Science (IISc) in Bangalore. IISc records that he became its first Indian director on 31 March 1933 and set up its Department of Physics the same year. Stepping down as director on 19 July 1937, IISc says, he stayed as Professor of Physics until his retirement in 1948. Students there included GN Ramachandran, S Ramaseshan and Vikram Sarabhai.

The reasons for 1937 are contested. According to his biographer G Venkataraman, Raman clashed with senior staff and council members after reorganising departments and moving part of the Institute’s budget to the new physics department, which brought charges of embezzlement. Venkataraman says the review committee appointed by the Viceroy “did what it was supposed to do, namely, slay Raman”. A letter of 1 June 1937 from Raman offered to end his contract as director. Venkataraman, who admired Raman, calls the struggle a battle between excellence and mediocrity. The committee’s own report is not among the sources used here, so this is one side of the quarrel.

By 1948 Raman had an institute of his own. The Raman Research Institute says the Government of Mysore gave a plot of land in Bangalore to Raman in December 1934, and that he founded the Institute in 1948 to continue basic research after leaving IISc and directed it until his death. The Nobel biography lists his laboratory’s work there as the structure and properties of diamond and the optics of iridescent substances such as opal, agate and pearls. Raman died in Bangalore on 21 November 1970.

National Science Day, held every 28 February, commemorates the Raman effect, the Press Information Bureau says. The National Council for Science and Technology Communication asked the government in 1986 to designate the day, the government agreed, and the first National Science Day was held on 28 February 1987.