Millimeter-Wave Rotational Stark Spectra of HNCO, DNCO, and HN3: Dipole-Moment Changes with <i>K</i>

Abstract

By employing a parallel-plate semifree-space cell the millimeter-wave rotational Stark spectra of HNCO, DNCO, and HN3 have been observed in the ground vibrational state. Analysis of the Stark effect for the J=3→4 transitions yields the dipole-moment component along the axis of smallest moment of inertia. For these very slightly asymmetric rotors the dipole moment is observed to decrease with increasing K. For HNCO (J=3→4), the dipole moments are found to be (Debye units) K=0, μa=1.613±0.002, K=2, μa=1.540±0.001,K=1, μa=1.575±0.002, K=3, μa=1.500±0.002;for DNCO (J=3→4), K=1, μa=1.602±0.003, K=2, μa=1.580±0.001;and for HN3 (J=3→4), K=1, μa=0.8369±0.0020, K=2, μa=0.8247±0.0002.The results are discussed in terms of the electronic structures of the molecules.