80 TH Anniversary of the discovery of the Raman Effect: a celebration

Eighty years ago on 31 March 1928, a letter dated 16 February was published in Nature by C. V. Raman (Fig. 1) and K. S. Krishnan with the title ‘A New Type of Secondary Radiation’. This letter, which is reproduced in Fig. 2, was the first account in the scientific literature of what soon became known as the Raman Effect. The experiments reported in this letter were based on the use of complementary light filters to detect the presence of modified scattered radiation using focused sunlight as an excitation source and the eye as a detector. Raman and his co-workers soon improved on this rather basic experimental procedure by using a spectroscope to examine the scattered radiation. The first Raman spectrum was reportedly obtained on 28 February 1928. On 29 February the Associated Press of India gave the first newspaper report under the heading ‘New Theory of Radiation – Prof. Raman’s Discovery’; and on 1 March 1928, The Statesman, an English language daily of Calcutta, carried an article with the title ‘Scattering of Light by Atoms – New Phenomenon – Calcutta Professor’s Discovery’ which is reproduced in Fig. 3. The paragraph heading ‘Two colours from one’ is attractive and accurate journalism, but there are several palpable scientific errors in the text. It has to be recognised that Raman’s earliest papers were couched in rather general terms and it was only in a letter submitted to Nature on 22 March and published on 5 May that a spectrum was presented, although spectra were included in a lecture by Raman in Bangalore on 16 March. Shortly after the publication of Raman and Krishnan’s letter in Nature, Landsberg and Mandelstam in Russia reported the observation of light scattering with change of frequency in quartz in a paper in Die Naturwissenschaften published on 13 July 1928 and reproduced here in Fig. 4. This paper was submitted on 6 May, one day after the official publication date of Raman and Krishnan’s definitive paper. Landsberg and Mandelstam could not have had any information in Moscow about this paper but they did refer to Raman’s earlier publications saying that they were unable to decide whether there was any connection with their work because Raman’s description was too brief and lacking in detail. The two discoveries must be regarded as quite independent. Although quantum theory was still in its infancy in the nineteen twenties, the Raman Effect had been predicted by quantum mechanics in two classic papers, one by Smekal1 published in 1923 and one by Kramers and Heisenberg2 in 1925. Figure 1. C. V. Raman.