# FT-MICROWAVE SPECTRUM, LARGE-AMPLITUDE MOTIONS, AND ab initio CALCULATIONS FOR $N_{2}O_{5}$

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 Title: FT-MICROWAVE SPECTRUM, LARGE-AMPLITUDE MOTIONS, AND ab initio CALCULATIONS FOR $N_{2}O_{5}$ Creators: Grabow, Jens-Uwe; Andrews, Anne M.; Suenram, R. D.; Fraser, G. T.; Lovas, F. J.; Domenech, J. L.; Lafferty, W. J.; Irikura, K. K. Issue Date: 1995 Publisher: Ohio State University Abstract: The Fourier-transform microwave spectrum of the highly reactive atmspheric reservoir $species^{1}$ $N_{2}O_{5}$, recently studied in the $mm-wave^{2}$ and extensively studied in the infrared, has been investigated. Our initial spectral searches were guided by the electron-diffraction $results^{3}$. Two b-type asymmetric-rotor-like spectra are observed, which fit poorly to a rigid-rotor Hamiltonian. Guided by ab initi and dynamical calculations which show a planar configuration is energetically unfavorable, these spectra are assigned to two of the tunneling states of the molecule arising from a geared internal rotation of the two $NO_{2}$ groups about their respective $C_{2}$ axes. Only 4 of the 10 rotational-tunneling species possible in the $G_{16}$ molecular symmetry group for this non-rigid molecule may be observed. This is due to the presence of the 4 equivalent spin-zero oxygen nuclei, which gives zero statistical weights for all but the ${A_{1}}^{+}, {A_{1}}^{-}, {A_{2}}^{+}$, and ${A_{2}}^{-}$ rotational-tunneling states. Consistent with the tunneling picture, the nuclear quadrupole hyperfine patterns demonstrate that the two nitrogen nuclei occupy dynamically equivalent positions. The hyperfine analysis further establishes that the two observed tunneling states are of ${A_{1}}^{+}$ and ${A_{1}}^{-}$ symmetry. Further analysis is being attempted to determine the barrier to internal rotation. Description: 1. G.C. Toon, C.B. Farmer, and R.H. Norton, Nature 319, 570 (1986). 2. J.-M. Colmont, J. Mol. Spectrosc. 155, 11 (1992). 3. B.W. McClelland, L. Hedberg, K. Hedberg, and K. Hagen J. Am. Chem. Soc. 105, 3789 (1983). Author Institution: National Institute of Standards Technology, Gaithersburg, MD 20899, USA.; Institute for Defense Analysis, 1801 N. Beauregard Street, Alexandia, VA 22311, USA.; CSIC, Serano 119, 28006 Madrid, Spain. URI: http://hdl.handle.net/1811/29605 Other Identifiers: 1995-RD-02