Smekal Raman effect

K. W. F. Kohlrausch, Der Smekal-Raman Effect, Springer, Berlin (1938)... 

It was predicted in 1923 by Smekal and shown experimentally in 1928 by Raman and Krishnan that a small amount of radiation scattered by a gas, liquid or solid is of increased or decreased wavelength (or wavenumber). This is called the Raman effect and the scattered radiation with decreased or increased wavenumber is referred to as Stokes or anti-Stokes Raman scattering, respectively. 

To conclude this section, there is one other phenomenon we should like to discuss, viz. the Raman effect. Let it be mentioned beforehand, however, that this is not a revolutionary discovery, like, for example, the discovery of the wave nature of the electron, but an effect which was predicted by the quantum theory (Smekal (1923), Kramers-Heisenberg) some years before it was found experimentally, though it can also be explained within the framework of classical physics (Cabannes (1928), Rocard, Placzek) its great importance rests rather on the facility with which it can be applied to the study of molecules, and on the colossal amount of material relating to it which has been accumulated so quickly. The effect was discovered simultaneously (1928) by Raman in India, and by Landsberg and Mandelstam in Russia. They found that scattered light contains, in addition to the frequency of the incident light, a series of other frequencies. 

In 1928, C.V. Raman announced the discovery of the effect that now bears his name. In fact he had already observed it a few years before as a weak residual fluorescence from highly purified organic liquids. It is generally considered, however, that the effect had been predicted by A. Smekal. Raman was awarded the Nobel Prize, the second Indian to be so honoured. Although the Raman effect was found to be very weak, the relation of selection rules to symmetry differed, so that results could complement those from IR absorbance. 

Inelastic photon scattering processes are also possible. In 1928, the Indian scientist C. V. Raman (who won the Nobel Prize in 1930) demonstrated a type of inelastic scattering that had already been predicted by A. Smekal in 1923. This type of scattering gave rise to a new type of spectroscopy, Raman spectroscopy, in which the light is inelastically scattered by a substance. This effect is in some ways similar to the Compton effect, which occurs as a result of the inelastic scattering of electromagnetic radiation by free electrons. 

Raman spectroscopy is a vibrational optical spectroscopic technique based on the inelastic scattering of light by matter like the molecule of interest. Raman spectroscopy is a highly specific technique due to specific molecular fingerprint information as observed in the Raman spectra. This phenomenon was theoretically predicted by Smekal in 1923 (Smekal 1923). In 1928, the first experimental observation of RS effect was reported by Indian physicists C.V. Raman and K.S. Krishnan (Raman and Krishnan 1928a, b) and independently by Mandelstam and... 

In 1923, SMEKAL [1.19] studied the scattering of light by a system with two quantized energy levels and predicted the existence of sidebands in the spectrum. This effect was subsequently observed by RAMAN and KRISHNAN [1.20] in 1928 they found that light scattered by liquids contains sharp sidebands... 

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