15min:

YU. A. BARANOV, Institute of Experimental Meterology, Taifun Research and Production Association, Obninsk, 249020 Russia; A. A. VIGASIN, Obukhov Institute of Atmospheric Physics, Pyzhevsky per 3, Moscow, 109017 Russia; W. J. LAFFERTY AND G. T. FRASER, Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, MD. 20899, USA.

Infrared spectra of O₂ and CO₂ mixtures were studied in the laboratory between 1100 cm^-1 and 1800 cm^-1 for temperatures from 220 K to 296 K and total pressures up to 500 kPa using a Fourier-transform infrared spectrometer and a 2-meter-long, multiple-pathlength, White cell operating at 84 m. The intensity of the O₂ continuum is strikingly enhanced by the addition of CO₂. This result contrasts with our observations on the CO₂ monomer and dimer lines, which show negligible enhancement upon the addition of O₂. The shape of the O₂ fundamental band sharpens with the addition of CO₂, and at lower temperatures apparent P, Q, and R-branch features appear, which are attributed to a CO₂--O₂ complex.

The observed CO₂ enhancement of the O₂ continuum absorption in the mid-infrared is consistent with our similar observations on the 1.27 µm near-infrared, magnetic-dipole band of O₂ . Our observations agree with the theoretical calculations by Brown and Tipping in which they predicted significant enhancements by H₂O vapor of the continuum absorption of N₂ and O₂ for the vibrational fundamentals, attributed to the large electric dipole moment of H₂O. We note that CO₂, like H₂O, has a large electrostatic moment, the electric quadrupole moment.