Millimeter wave spectroscopy of Ne-CO

The pure rotational b-type spectrum of the van der Waals complex Ne-CO has been measured using a pulsed jet, intracavity millimeter wave spectrometer. The millimeter wave generation is based on the OROTRON principle. The high sensitivity of the spectrometer allowed measurements of R(J), K = 1 <-- 0 transitions between 108 and 150 GHz of the Ne isotopomers Ne-20-CO and Ne-2 2-CO. This new millimeter wave data set together with the microwave data in the literature, i.e. a-type microwave transitions, yield in a fit to an as ymmetric rotor a reliable set of ground state constants. These are for Ne-2 0-CO: A = 107127.021(14) MHz, B = 3479.6597(95) MHz, and C = 3039.5387(93) MHz. For both Ne-20-CO and Ne-22-CO, a global fit to a near-symmetric rotor was performed, taking into account the infrared and microwave transition f requencies from the literature and the millimeter wave measurements of the present work.