Rappal Sangameswara Krishnan obtained the DSc degree (1937) from the University of Madras and PhD (1941) from the University of Cambridge, UK. His specialization was in light scattering, colloid optics, nuclear physics, Raman & infrared spectroscopy, brillouin scattering, X-ray diffraction, crystal physics, solid-state physics, lasers, geochronology and ultrasonics. He was Professor & Head, Department of Physics, Indian Institute of Science, Bangalore (1948-70); UGC Retired Scientist (1972-73) and Vice-Chancellor, Kerala University, Thiruvananthapuram (1973-77). From 1977 onwards, he undertook projects from DST and on Documentation of Raman Effect Data at IISc (1977-82); CSIR, Source Book on Raman Effect and was attached as Visiting Scientist to National Aerospace Laboratory, Bangalore (1987-90); after which he was CSIR Emeritus Scientist.
Academic and Research Achievements: Krishnan discovered a new optical effect named after him. While at Cavendish Laboratory, he demonstrated the existence of deuteron-tritium reaction and was the first to establish the deuteron-induced fission in uranium and thorium. At IISc, he developed the ultraviolet (mercury 2536 Å) technique of excitation for Raman spectroscopy and successfully recorded for the first time the second-order Raman spectra of diamond and alkali halides, providing experimental confirmation of Born's lattice dynamical theory. This was the starting point for investigations on lattice dynamics of crystals in many laboratories in the world. Also, for the first time, Krishnan made Brillouin scattering experiments in diamond, crystalline and fused quartz, alumina and alkali halides. With his student Chandrasekharan he worked out the theory of Brillouin scattering in cubic and birefringent crystals. With his coworkers he investigated the thermal expansion, elastic constants and photoelastic constants of crystals. He also initiated work on dating of Indian rock formations using nuclear geochronological techniques. Krishnan authored a monograph and contributed many chapters to standard works. He wrote two volumes of 'Source Book on Raman Effect'.
Other Contributions: Krishnan established an active school of research in many branches of solid-state physics at IISc, now recognized as a leading centre for research in this area in India. He was member of International Committee on Ferro-electricity and International Advisory Committee for Conferences on Raman Spectroscopy.
Awards and Honours: Krishnan received the Platinum Jubilee Distinguished Alumni Award of IISc (1984) and Sir CV Raman Centenary Gold Medal (1988). He was a Fellow of the American Physical Society; Indian Academy of Sciences, Banglaore and Institute of Physics, London. He was President, Physics Section of Indian Science Congress (1949).