The rotational spectra of the ground and first excited bending states of deuterium isocyanide, DNC, up to 2 THz

Abstract The pure rotational spectrum of deuterium isocyanide (DNC) was recorded in the frequency range from approximately 680 to 1985 GHz. Twenty-one new transitions in the vibrational ground and first excited bending states (01 e,f 0) have been assigned, namely R -branch transitions from J =9←8 to 25←24. In a least squares analysis of these new transition frequencies together with previously reported millimeter-wave data, spectroscopic parameters up to sextic order could be derived with high precision for both states. Furthermore, the l-type doubling constant q and its centrifugal distortion terms q J and q JJ were obtained for the first excited bending state.