A new millimeter-wave observation of the weakly bound CO–N2 complex

Abstract

New millimeter-wave transitions of the CO–N2 van der Waals complex have been observed using the intracavity OROTRON jet spectrometer in the frequency range of 103–159GHz. For the less abundant form, CO–paraN2, a total of 37 rotational transitions were assigned to three K=0–0, 0–1, 2–1 subbands connecting the (jCO, jN2)=(1,1) and (jCO, jN2)=(0,1) internal rotor states. The upper K=0 and K=2 “stacks” of rotational levels were probed for the first time here by millimeter-wave spectroscopy following a recent infrared study by Rezaei et al. (2013). The observation of new subbands fixes with higher precision not only these upper K=0 and K=2 but also lower K=1(f) levels, not linked with other stacks in earlier rotational studies. For the more abundant form, CO–orthoN2, five new P-branch rotational transitions of the K=0–0 “CO bending” subband are reported, thus extending previous measurements. Nuclear quadrupole hyperfine structure due to the presence of two equivalent 14N nuclei was partly resolved and analyzed to give additional information about the angular orientation of the N2 molecule in the complex.