The Raman effect in X-ray scattering

Abstract

That a quantum of radiation can be absorbed in part by an atomic system, and the remaining part scattered by it giving rise to a radiation of increased wave-length, has been demonstrated by recent work on the scattering of light in material media. In his address on New Radiation (Ind. Jour. Phys., vol. 2, p. 398, Mar. 31, 1928) Raman pointed out that precisely similar effects should also be observable in the case of X-ray scattering. In other words, in addition to the Compton type, we should also have other modified X-radiations scattered by the atom, in which the scattering electrons alter their positions in the atom, but remain bound to it. The frequencies of the radiations scattered by the atom would be where σ is the incident frequency, Ek is the energy of the initial level and El of the final level of the electron. When El is positive, it may have an arbitrary value, and, as has been shown by Wentzel and others, the scattered radiation is of the Compton type, in which the change of wave-length depends on the direction of observation. On the other hand, when El is negative, the electron remains bound to the atom, and we have a type of X-ray scattering completely analogous to that observed in the optical case. The frequency of the Raman type of X-ray scattering is independent of direction and is as sharply defined as that of the unmodified radiation.