MILLIMETER-WAVE SPECTRUM OF THE NO DIMER

The pure rotational spectrum of the NO dimer, ((NO)-N-14-O-16)(2), has been studied in the 225-400 GHz millimeter-wave region by means of di rect absorption in a supersonic jet expansion. Previously, only 4 rota tional transitions of (NO)(2) had been measured in the microwave regio n. To these, we have added 66 new millimeter-wave transitions with val ues of J ranging from 4 to 16 and of K-a, from 2 to 7. Most transition s were observed as single lines, but a few showed partially resolved h yperfine structure. The analysis of these data, in combination with th e previous microwave transitions and an extensive set of infrared (nu( 1), band) measurements, has resulted in a greatly improved set of para meters for the ground state of the NO dimer, including the first sexti c distortion parameters. (C) 1997 Academic Press.