NITROGEN BROADENING AND SHIFT COEFFICIENTS IN THE $\nu_{5}$ AND $\nu_{6}$ FUNDAMENTAL BANDS OF $^{12}CH_{3}D$
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Date
2000
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Ohio State University
Abstract
A multispectrum nonlinear least-squares sitting $technique^{a}$ has been used to determine Lorentz $N_{2}$-broadening and pressure-induced shift coefficients for a large number of transitions in the $\nu_{3}$ and $\nu_{6}$ fundamental bands of $^{12}CH_{3}D$ in the region from 1060 to $1640 cm^{-1}$. We analyzed a total of 17 high-resolution (0.002 to $0.006 cm^{-1})$ room temperature absorption spectra recorded with the Bruker IFS 120 HR at PNNL and the 1-m Fourier transform spectrometer (FTS) at the McMath-Pierce facility of the National Solar Observatory at Kitt Peak. Our multispectrum analysis technique allowed us to simultaneously analyze both self-broadened and $N_{2}$-broadened spectra. The data set included 13 spectra of 98% pure $CH_{3}D$ at pressures of 0.1 to 303 torr in cells with path lengths of 10 to 2486 cm and 4 spectra of lean mixtures $(\approx 1%)$ of $CH_{3}D$ in research grade nitrogen at total pressures between 100 and 400 torr in a 25 cm cell. $N_{2}$-broadening coefficients for over 800 transitions and shift coefficients for more than 600 transitions in the $\nu_{3}$ and $\nu_{6}$ bands were determined. Transitions with rotational quantum numbers up to $J^{\prime\prime} = 15$ and $K^{\prime\prime} = 14$ were analyzed, $N_{2}$- broadening coefficients were measured in all six $\nu_{6}$ sub-bands $(^{P}P, ^{P}Q, ^{P}R, ^{R}P, ^{R}Q$ and $^{R}R$). The measured broadening coefficients vary from about 0.02 to $0.09 cm^{-1}$ $atm^{-1}$ at 296K. Most of the measured pressure-shift coefficients are negative with values extending from about $-0.014 to +0.005 cm^{-1} atm^{-1}$. Very few of the measured shift coefficients are positive, and the positive shifts are mostly associated with the $J^{\prime\prime} = K^{\prime\prime}$ transitions in the $^{P}Q$ sub-bands. $J^{\prime\prime} = K^{\prime\prime}$ transitions are also associated with the smallest broadening coefficients in both the $\nu_{5}$ 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: Department of Physics, The College of William and Mary; Atmospheric Sciences, NASA Langley Research Center; Jet Propulsion Laboratory, California Institute of Technology; Jet Propulsion Laboratory, Pacific Northewest National Laboratory (PNNL)
Author Institution: Department of Physics, The College of William and Mary; Atmospheric Sciences, NASA Langley Research Center; Jet Propulsion Laboratory, California Institute of Technology; Jet Propulsion Laboratory, Pacific Northewest National Laboratory (PNNL)