CONTINUUM ABSORPTION IN THE REGION OF THE $O_{2}$ VIBRATIONAL FUNDAMENTAL BAND IN $O_{2}$ AND $CO_{2}$ MIXTURES AT TEMPERATURES RANGING FROM 220 K TO 296 K
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Date
2002
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Publisher
Ohio State University
Abstract
Infrared spectra of $O_{2}$ and $CO_{2}$ 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 $O_{2}$ continuum is strikingly enhanced by the addition of $CO_{2}$. This result contrasts with our observations on the $CO_{2}$ monomer and dimer lines, which show negligible enhancement upon the addition of $O_{2}$. The shape of the $O_{2}$ fundamental band sharpens with the addition of $CO_{2}$, and at lower temperatures apparent P, Q, and R-branch features appear, which are attributed to a $CO_{2}-O_{2}$ complex. The observed $CO_{2}$ enhancement of the $O_{2}$ continuum absorption in the mid-infrared is consistent with our similar observations on the $1.27 \mu m$ near-infrared, magnetic-dipole band of $O_{2} {^{a}}$. Our observations agree with the theoretical calculations by Brown and Tipping ${_{b}}$ in which they predicted significant enhancements by $H_{2}O$ vapor of the continuum absorption of $N_{2}$ and $O_{2}$ for the vibrational fundamentals, attributed to the large electric dipole moment of $H_{2}O$. We note that $CO_{2}$, like $H_{2}O$, has a large electrostatic moment, the electric quadrupole moment.
Description
$^{a}$G. T. Fraser and W. J. Lafferty, J. Geophys. 106 31749 (2001). $^{b}$A. Brown and R. H. Tipping, private communication.
Author Institution: Institute of Experimental Meterology, Taifun Research and Production Association; Obukhov Institute of Atmospheric Physics, Pyzhevsky per 3; Optical Technology Division, National Institute of Standards and Technology
Author Institution: Institute of Experimental Meterology, Taifun Research and Production Association; Obukhov Institute of Atmospheric Physics, Pyzhevsky per 3; Optical Technology Division, National Institute of Standards and Technology