Millimeter-Wave Spectrum of the NO Dimer

The pure rotational spectrum of the NO dimer, (14N16O)2, has been studied in the 225-400 GHz millimeter-wave region by means of direct absorption in a supersonic jet expansion. Previously, only 4 rotational transitions of (NO)2 had been measured in the microwave region. To these, we have added 66 new millimeter-wave transitions with values of J ranging from 4 to 16 and of Ka from 2 to 7. Most transitions were observed as single lines, but a few showed partially resolved hyperfine structure. The analysis of these data, in combination with the previous microwave transitions and an extensive set of infrared (nu1 band) measurements, has resulted in a greatly improved set of parameters for the ground state of the NO dimer, including the first sextic distortion parameters. Copyright 1997 Academic Press. Copyright 1997Academic Press