Investigation of gases by the method of nonlinear absorption spectroscopy

An investigation is made of the possibility of using nonlinear absorption spectroscopy in the analysis of gas mixtures. This method enables accurate concentration measurements to be made in those spectral regions where normal spectroscopic methods are inaccurate because of the overlapping of the neighboring absorption lines. It was used to study hydrocarbons in the Zeeman tuning range of a He–Ne laser with λ = 3.39 μ. The promise shown by this method in studies of isotopic mixtures is remarked upon.