Terahertz spectroscopy of N$^{18}$O and isotopic invariant fit of several nitric oxide isotopologs

摘要

A tunable far-infrared laser sideband spectrometer was used to investigate anitric oxide sample enriched in 18O between 0.99 and 4.75 THz. Regular,electric dipole transitions were recorded between 0.99 and 2.52 THz, whilemagnetic dipole transitions between the 2Pi(1/2) and 2Pi(3/2) spin-ladders wererecorded between 3.71 and 4.75 THz. These data were combined with lowerfrequency data of N(18)$O (unlabeled atoms refer to (14)N and (16)O,respectively), with rotational data of NO, (15)NO, N(17)O, and (15)N(18)O, andwith heterodyne infrared data of NO to be subjected to one isotopic invariantfit. Rotational, fine and hyperfine structure parameters were determined alongwith vibrational, rotational, and Born-Oppenheimer breakdown corrections. Theresulting spectroscopic parameters permit prediction of rotational spectrasuitable for the identification of various nitric oxide isotopologs especiallyin the interstellar medium by means of rotational spectroscopy.