Sum-Frequency-Generated Spectra of Gases and Liquids

Abstract

The theory of sum‐frequency‐generated spectra of gases and liquids is derived for the case of resonance. Our results are in agreement with the previously derived nonresonance theories by Giordmaine and others. It is suggested that the resonance case can be studied by means of an experiment where one of the incident beams comes from a laser source while the other incident beam is ordinary polarized monochromatic light of variable frequency.