Discovery of the rotational spectrum of the weakly bound complex CO-H-2

Rotational transitions of the CO-H-2 van der Waals complex have been measur ed between 108 and 125 GHz in a supersonic jet. Three absorption lines were recorded and assigned as belonging to CO-paraH(2) with a new highly sensit ive intracavity spectrometer based on the millimeter wave generator, called OROTRON. The results provide confirmation of the recent infrared data of M cKellar at 4.7 mu m, enabling a more precise determination of the energies of the rotational levels with different parity in the vibrational ground st ate. The measured millimeter wave transitions provide precise frequencies f or an astronomical search of CO-parnH(2). (C) 1999 Elsevier Science B.V. Al l rights reserved.