Raman’s momentous discovery in 1928 that the spectral analysis of the light scattered by matter, illuminated with monochromatic light of frequency ω L, reveals new signatures at (ω L ± ω i) , ω i’s being the internal frequencies of the matter [Nature 121, 501 (1928); Indian Journal of Physics 2, 387 (1928)]. In a cable to Nature [ 122, 349 (1928)], R.W. Wood, the renowned American Physicist, hailed it as a “very beautiful discovery, which resulted from Ramans’s long and patient study of the phenomenon of light scattering” and underscored its significance as “one of the most convincing proofs of the quantum theory of light we have at present time”.
After a brief account of Raman’s extraordinary scientific career, I will recount the profound impact made by Raman effect, which launched a new branch of spectroscopy, with two illustrative examples: (1) Rotational Raman Spectra of homonuclear diatonic gases and Bose-Einstein & Fermi-Dirac Statistics and (2) The parity related rule of mutual exclusion in the Raman vs infrared activity of vibrational modes of centro-symmetric matter.
The dramatic change and the vastly expanded scope of Raman spectroscopy brought about by the invention of the Laser in 1960 will be illustrated with select examples from Condensed Matter Physics and Materials Science. In particular, the focus will be on the collective and localized vibrational, electronic, and magnetic excitations in semiconductors and their nanostructures.