The rQKa, branches of carbodiimide, HNCNH, between 1.8 and 3.3 THz

Year: 1995

Authors: Wagener V., Winnewisser M., Bellini M.

Autors Affiliation: Physikalisch-Chemisches Instituí, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-3539 Giessen, Germany; European Laboratory for Nonlinear Spectroscopy (LENS), Largo Enrico Fermi, 2, 1-50125 Florence, Italy

Abstract: The rQKa branches of carbodiimide, HNCNH, have been recorded with a tunable far-infrared spectrometer. The rQKa branches with Ka ? { 2, 3, 4 }, which occur at approximately 1.8, 2.5, and 3.2 THz, respectively, were measured rotationally resolved. The torsional doublet splitting observed in the rQ0 branch and several rR branches by Birk et al. (J. Mol. Spectrosc.136, 402-445 (1989)) was also observed in all the Q branches reported here. In addition, anomalous Ka-type doubling was detected within the rQ2 branch for rotational quantum numbers J > 18. Molecular constants were obtained by fitting the line positions, including older data, with Watson\’s Hamiltonian in S-reduction. The anomalous Ka-type doubling could be described as a centrifugal distortion interaction with ?Ka = 4. The splitting is called anomalous because it inverts the Ka = 2 energy levels of an accidentally nearly prolate symmetric top molecule (Ray\’s asymmetry parameter for HNCNH ? = -0.999995343(32)).

Journal/Review: JOURNAL OF MOLECULAR SPECTROSCOPY

Volume: 170 (2)      Pages from: 323  to: 334

KeyWords: Wave rotational spectrum; HSSH; Dynamics; DSSD
DOI: 10.1006/jmsp.1995.1074

Citations: 10
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