Raman Spectra of Solutions of Some Ionized Substances
A new type of secondary radiation has recently been found  to be present in the light scattered by liquids. If a medium is illuminated with a monochromatic radiation for which it is largely transparent, the scattered light is found to contain in addition to light of the original frequency, lines of altered frequency which do not arise from fluorescence. A characteristic of this phenomenon, the Raman Effect, is that the changes in frequency on scattering are independent of the frequency of the incident radiation. The changes in frequency are, however, specifically dependent on the nature of the scattering substance and, indeed, are often found to I agree with previously known infra-red frequencies of the substance. There is little doubt that the frequency changes on scattering measure differences in the energy contents of stationary states of the molecules of the scattering substance.
Copyright © 1929 by the National Academy of Sciences Communicated February 28, 1929 We are indebted to Professor Ira S. Bowen for valuable advice relative to the present measurements.