Session 17 - The Galactic Interstellar Gas.
Display session, Monday, January 13
Metropolitan Ballroom,

## [17.09] A Search for the CO-H2 dimer in the Galaxy

R. J. Allen, L. Loinard (STScI), A. R. W. McKellar (NRC of Canada), J. Lequeux (DEMIRM, Obs. de Paris)

We have used the 30m IRAM millimeter radio telescope to search for two low-lying rotational transitions of the CO-H_2 dimer in the emission spectra of 3 Galactic sources and in the absorption spectrum of a low-latitude extragalactic continuum source. The transitions are the 111- \leftrightarrow 000+ line at 109.21 GHz, and the 110+ \leftrightarrow 101- line at 90.84 GHz. The search targets were the TMC 1 and L 134 dark clouds, the L 1157 bipolar outflow, and the compact radio continuum source 2013+370. The spectral search covered the frequency ranges from 90.58 - 91.10 GHz and from 108.95 - 109.46 GHz. Several known emission lines were found including HC_3N(12-11), HC_3N(10-9), OCS, SO, and HNC, but no other features were seen in the spectra. The rms noise was typically 5 mK per 1 MHz channel (\approx 3 km s^-1).