Raman effect of multiple radiation process and its applications in spectroscopy

TLDR: In this article, it was shown that with a beam intensity of 0.1 MW/sq cm, the vibrational Raman spectrum of molecules or crystals may be obtained by the three-photon process.

Abstract: : It may become possible to observe the third-order process of radiation in the strong electromagnetic field of a laser beam with two photons absorbed and a third one emitted during a transition between energy levels of a material system. This process is analogous to the ordinary Raman effect, in which only two photons are involved. A theoretical analysis is given and the conclusion reached that with a beam intensity of 0.1 MW/sq cm, the vibrational Raman spectrum of molecules or crystals may be obtained by the three-photon process. It is shown that this effect actually offers a new spectroscopic method. Its importance lies in the difference of the selection rule of this effect and that of the infrared absorption and the ordinary Raman effect. It is also pointed out that the stimulated radiation of three-photon Raman effect may be realized when pumped with a powerful laser beam. (Author)