MOLECULAR PARAMETERS FOR THE $COF_{2}$ BANDS NEAR 16.6$\mu$ AND 5.2$\mu$
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Date
1992
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Publisher
Ohio State University
Abstract
The 16.6 $\mu$m Fourier transform infrared spectra of the $COF_{2}$ $v_{3}$ and $v_{5}$ bands at 581.7 and $619.1 cm^{-1}$ were recorded at an unapodized resolution $0.001 cm^{-1}$ using a Bruker FT spectrometer. The spectra were fitted using a two band Hamiltonian which treats the c-type Coriolis coupling between the bands exactly. The fitted data included published microwave spectra of the excited states as well as additional microwave and millimeter measurements done in our laboratory. The millimeter data showed in detail a $\Delta K_e=4$ avoided crossing in which $v_{3}$, $K_{2}=24$ and $v_{5}$, $K_c=28$ strongly interact n ear $J=42$. Several perturbation allowed transitions were observed. All data up to $J^{\prime}=75$ were fitted to within experimental uncertainty using only rotational, quartic centrifugal distortion, and Coriolis coupling constants for the upper states as well as ground state constants fixed to published values. For this fit and the one described below the upper state sextic constants were fixed to those of the ground state. The RMS deviations of 942 IR and 108 microwave features were $0.00013 cm^{-1}$ and 35 kHz respectively. These results along with published parameters for the $\nu_{3}$ band provided initial estimated of effective upper state rotational constants and the band origin for the 2 $\nu_{3}+\nu_{3}$ band which interacts with the 5.2$\mu$ $\nu_{1}$ band via a b-type Coriolis interaction. These estimates were essential for a fit of the $\nu_{1}$, $2\nu_{2}$, $2\nu_{3} + \nu_{6}$ triad at 1944.6, 1913.8, and $1937.3 cm^{-1}$ in which the Coriolis coupling and the Fermi resonance between $\nu_{1}$ and $2\nu_{2}$ were treated simultaneously. There are several avoided crossings for $\Delta K_e=2$ between $\nu_{1}$ and 2 $\nu_{2}$ for $\Delta K_e=1$ and 3 between $\nu_{1}$ and $2\nu_{3} +\nu_{6}$. A RMS deviation of $0.00032 cm^{-1}$ was obtained in the fit of 1270 features up to $J^{\prime}=63$ for $\nu_{1}$, $J^{\prime}=58$ for $2\nu_{2}$, and including more than 20 perturbation allowed transitions of 2 $\nu_{3} +\nu_{8}$. The spectra used in the analysis were obtained with the FTS at Kitt Peak National Laboratory at $0.0028 cm^{-1}$ unapodized resolution. With these studies, all fundamentals of $COF_{2}$ have been studied at high resolution.
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Author Institution: Jet Propulsion Laboratory, California Institute of Technology