LINE STRENGTHS AND LINE MIXING IN THE $791 cm^{-1}$ Q BRANCH OF CO2
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Date
1990
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Ohio State University
Abstract
The $791 cm^{-1}$ Q branch of $CO_{2}$ will be used by the CLAES (Cryogenic Limb Array Etalon Spectrometer) instrument on UARS (Upper Atmosphere Research Satellite) for stratospheric temperature sounding. We have measured the strengths of a number of lines in the Q and R branches of this band using a tunable diode laser spectrometer. The line strengths are derived from the spectra using a modified equivalent width method that minimizes uncertainties in the 100\% transmission background. Our results are compared to recent measurements of this band by Dana $et. al.^{1}$ Spectra of this Q branch with total pressures between 100 and 740 torr, both self- and $N_{2}$-broadened, were also recorded. We find excellent agreement between experiment and calculation for the self-broadened spectra using a simple energy gap scaling law to determine the off-diagonal collisional relaxation matrix. Although our calculations account for most of the line mixing in the $N_{2}$-broadened spectra, we systematically underestimate the amount of line mixing by a small amount. This behavior has also been seen in other $CO_{2}$ Q branches, both in the laboratory and in atmospheric spectra. The ramification of this disagreement for the energy gap scaling law used in this work will be discussed.
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$^{1}$ V. Dana, A. Valentin, A. Handouni, and L. Rothman, A.O. 28, 2562 (1989).
Author Institution: Department of Physics, University of Maryland Baltimore County
Author Institution: Department of Physics, University of Maryland Baltimore County