INFRARED SPECSTRUM OF CO-Ne COMPLEXES IN THE 4.7 $\mu$m REGION

1. A.R.W. McKellar, Y.P Zeng, S.W. Sharpe, C. Wittig, and R.A. Beaudet, J. Mol. Spectrose. 153, to be published (1992).Author Institution: Herzberg Institute of Astrophysics, National Research Council of Canada; Physical Chemistry Laboratory, Oxford UniversityThe spectrum of CO-Ne accompanying the fundamental band of CO around $2140 cm^{-1}$ has been studied in Ottawa using a long-path low-temperature static gas cell with a Bomem FT spectrometer, and in Oxford using a pulsed supersonic jet and a tunable diode laser spectrometer. The broad coverage and higher temperature (50 K) of the FT spectra are complemented by the higher resolution and simpler structure of the low temperature (=2 K) jet spectra. Like $CO-Ar,^{1}$ the spectrum can mostly be understood as a perpendicular band of a roughly T-shaped complex. Thus we have observed and assigned the strong $K_{a} = 1\leftarrow0$ and $0\leftarrow1$ subbands with J-values up to about 17. The $K_{a} =2\leftarrow1$ and $1\leftarrow2$ subbands are also observed in the FT spectrum, but are not yet assigned in detail. However, unlike CO-Ar, we also observe the weak parallel subband with $K_{a} =0\leftarrow0$, as well as the bending combination band with $v_{2}= 1\leftarrow0$ and $K_{a}= 0\leftarrow0$. The overall band origin is about $2143.197 cm^{-1}$, which represents a shift of only $-0.075 cm^{-1}$ from the CO monomer vibrational frequency, and the bending frequency for the complex is found to be about $8.5 cm^{-1}$. The effective B rotational constant of CO-Ne in its $c_{CO}=v_{2}=K_{a}=0$ ground state is $0.10868 cm^{-1}$, which gives an average intermolecular separation of about 3.647 \AA. The status of further experiments using $^{22}Ne$, and of the interpretation of the data in terms of the CO-Ne intermolecular potential surface will be discussed