Rotational spectrum of the N 2··CO complex: ortho-N 2 and para-N 2

Abstract

Pure rotational spectra of 14 N 2 ··CO, 15 N 14 N ··CO, and 15 N 2 ··CO have been observed using a Fourier transform microwave spectrometer. Two sets of transitions with J=2←1, 3←2, and 4←3 were observed for 14 N 2 ··CO and 15 N 2 ··CO; transitions with smaller effective rotational constants B were stronger than those with larger B for the 14 N 2 ··CO complex, while the opposite was observed for 15 N 2 ··CO. It was concluded that for 14 N 2 ··CO the first set corresponds to the K=0 stack of ortho-N 2 and the second to K=1 of para-N 2 based on a previous infrared analysis, hyperfine splittings, and the spin statistical weights. In the case of 15 N 14 N ··CO, only one set was observed because of the lack of symmetry. The electric quadrupole coupling constant of 14 N is much smaller, while the centrifugal distortion constant is much larger, than those of related complexes.