Investigation of weak absorption and gain lines of some gases by the method of selective losses in a laser resonator

The method of selective losses in a laser resonator was used in recording the absorption spectra of CO₂, CH₄, NH₃, C₂H₂, and C₂HD characterized by absorption coefficients down to 10^–7 cm^–1. It was found that quantitative measurements of the absorption coefficient could be made by this method. The same method made it possible to detect small amounts of isotopically substituted matter. Apart from weak absorption lines, we also observed weak gain profiles. Excited and short-lived states of the products of chemical reactions between radicals and molecules could be detected because of the high time resolution of the method.