NITROGEN- AND SELF-BROADENING AND SHIFT COEFFICIENTS IN THE $\nu_{3}$ FUNDAMENTAL BAND OF $^{12}CH_{3}D$
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Date
2000
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Ohio State University
Abstract
A multispectrum nonlinear least-squares fitting $technique^{a}$ has been used to determine Lorentz broadening and pressure- induced shift coefficient for a large number of transitions in the $\nu_{3}$ fundamental band of $^{12}CH_{3}D$ in the region from 1150 to $1430 cm^{-1}$. We analyzed a total of 14 high-resolution $(0.006 cm^{-1})$ room temperature absorption spectra recorded with the 1-m Fourier transform spectrometer (FTS) at the McMath-Pierce facility of the National Solar Observatory at Kitt Peak. The data set included 10 spectra of 98% pure $CH_{3}D$ and 4 spectra of $CH_{3}D$ in $N_{2}$. Our multispectrum analysis technique allowed us to simultaneously analyze both self-broadened and $N_{2}$-broadened spectra. The measurements in the $\nu_{3}$ band included transitions with rotational quantum number as high as $J^{\prime\prime} = 16$ and $K^{\prime\prime} = 16$. We determined $N_{2}$-broadening and shift coefficients for about 300 transitions and self-broadening and shift coefficients for over 400 transitions. The broadening coefficients (both self and $N_{2}$) range between 0.02 and $0.10 cm^{-1} atm^{-1}$ 2 at 296K. Both the self-shift and the $N_{2}$-shift coefficients vary between about -0.012 and $+0.009cm^{-1}$ $atm^{-1}$. At least 95% of the measured shift coefficients are negative, and the small number of positive shift coefficients often involve transitions with $J^{\prime\prime} = K^{\prime\prime}$. The $J^{\prime\prime} = K^{\prime\prime} $ transitions in the $^{Q}Q$ sub-band show the smallest broadening coefficients. The present results will be compared to previous measurements in this parallel band in the nearby perpendicular $\nu_{5}$ and $\nu_{6}$ bands.
Description
$^{a}$D. Chris Benner, C.P. Rinsland, V. Malathy Devi, M.A.H. Smith, and D. Atkins, JQSRT 53, 705-721 (1995).
Author Institution: Atmospheric Sciences, NASA Langley Research Center; Department of Physics, The College of William and Mary; Jet Propulsion Laboratory, California Institute of Technology
Author Institution: Atmospheric Sciences, NASA Langley Research Center; Department of Physics, The College of William and Mary; Jet Propulsion Laboratory, California Institute of Technology