The Rotational-Translational Spectra of N2 and CO2 and their Mixtures with Argon: Experimental Investigation

Abstract

The rotational-translational absorption spectra of carbon dioxide, nitrogen, and their mixtures with argon in the wavelength range 20-190 cm^-1 are obtained and analysed as a result of molecule pair collisions. It is demonstrated that, in contrast to absorption in noble gas mixtures, quadrupole interactions dominate the terahertz spectra of N₂ and CO₂. The overlapping mechanism was estimated to play a role in the formation of these spectra, and the quadrupole moments of the N₂ and CO₂ molecules, equal to 1.5-1.7 10^-26 CGSE and 4.25 10^-26 CGS, respectively, were calculated from the integrated intensity of the recorded spectra. To correct the calculation of the value of the quadrupole moments of the CO₂ from the intensity of the rotational- translational spectrum of pure CO₂, the Kihara potential was used as the interaction potential instead of the Lennard- Jones potential, which more accurately than the Lennard-Jones potential conveys the peculiarities of the interaction of molecules like CO₂. The quadrupole moments calculated from the spectra of N₂ CO₂ and their mixtures with argon are in good agreement with those obtained by other methods. The results obtained indicate that the study of the rotational-translational spectra of simple molecules is promising for determining their molecular constants.