A high-resolution spectroscopic study has been made of the emission in the 4.3-µ region of electrically excited CO2—N2 and CO2—N2—He plasmas. CO2-rich plasmas emit an intense spectrum in which P-branch and low-JR-branch lines appear in absorption. The R-branch band heads (J≅120) appear as emission features in such spectra and there is a region of mixed absorption and emission. CO2—N2 plasmas which would sustain laser oscillations in a suitable cavity exhibit emission lines and derive most of their intensity from the fundamental and four hot bands of the naturally abundant CO2 isotope. With the mixture ratio and pressure carefully adjusted, the CO2—N2—He plasma emits lines of the 00°3-00°2 and 00°2-00°1 bands. Bands from 13C16O2, 12C16O18O, and 13C16O18O, which are prominent in the CO2 absorption spectra, do not appear in the plasma spectra. The molecular constants ω30, x033, and y333 are derived from bands in the 00ν3-00(ν3-1) sequence.
T. K. MCCUBBIN, JR. and YU HAK HAHN, "Infrared Emission of CO2—N2 and CO2—N2—He Plasmas," J. Opt. Soc. Am. 57, 1373-1375 (1967)