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1Author    Kirsten Vormann, Helmut DreizlerRequires cookie*
 Abstract    o ro n a n d N itr o g e n H y p e rfin e S tr u c tu r e in th e R o ta tio n a l S p e c tr u m o f A m in o d iflu o ro b o ra n e The boron and nitrogen hyperfine structure in the rotational spectra of aminodifluoroborane has been investigated and the quadrupole coupling constants of1 and nitrogen have been determined. We get the following results for the nuclear quadrupole coupling constants: ^aa(n B) = —1.971 (6) MHz, xbh(11B) = -0.500(11) MHz, *cc(n B) -2.471 (11) MHz, and *aa(14N) = 0.890 (5) MHz, Zbfc(14N) = 2.303 (7) MHz, xcc(14N) = -3.193 (8) MHz. Additionally we determined rotational and centrifugal distortion constants according to Watson's A reduction. 
  Reference    Z. Naturforsch. 46a, 909—913 (1991); received July 11 1991 
  Published    1991 
  Keywords    Microwave spectroscopy, nuclear quadrupole hyperfine structure, aminodifluoroborane 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-0909.pdf 
 Identifier    ZNA-1991-46a-0909 
 Volume    46 
2Author    Jürgen Preusser, Manfred WinnewisserRequires cookie*
 Title    Nuclear Quadrupole Hyperfine Structure of the Direct /-Type Transitions of the Fulminic Acid Isotopomers H 12 C 14 N 16 0 and H 13 C 14 N 16 0  
 Abstract    The direct I-type transitions of H l3 C ,4 N l6 0 in the vibrational states (i^i's) = (01) and (03) were measured in the frequency range from 18 to 40 GHz. These transitions show a nuclear quadrupole hyperfine structure caused by the l4 N nucleus, which could partially be resolved at Doppler-limited resolution. The analogous transitions of the parent species. H l2 C l4 N 16 0, were remeasured. They displayed a very similar hyperfine structure, also partially resolved. The hyperfine patterns of both H l2 C l4 N l6 0 and H 13 C 14 N 16 0 were analysed by means of contour fitting s to the absorption profiles. The parameter l^eQq, which is responsible for the splittings, is determined to be 645(20) kHz for the vibrational state (01) and 890(44) kHz for the vibrational state (03) for H l2 C l4 N l6 0 and 642(32) kHz for (01) and 898(22) kHz for (03) for H 13 C l4 N 16 0. This unexpectedly large splitting parameter for states involving the large amplitude motion (HCN bending) is discussed as another consequence of the quasilinearity of fulminic acid, in view of the fact that the analogous transitions for the vibrational state (10) (NCO bending) do not split or even show a significant line broadening at the resolution used for the present measurements. 
  Reference    Z. Naturforsch. 51a, 207—214 (1996); received February 17. 1996 
  Published    1996 
  Keywords    Nuclear quadrupole hyperfine structure, quasilinear molecule, microwave spectroscopy 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0207.pdf 
 Identifier    ZNA-1996-51a-0207 
 Volume    51 
3Author    H. Dreizler, N. HansenRequires cookie*
 Title    High Resolution Microwave Spectroscopy of Ethyl Vinyl Ether: Accurate Determination of the Methyl Top Internal Rotation Barrier  
 Abstract    We have performed an investigation of the internal rotation of the methyl group in trans-cis ethyl vinyl ether by using molecular beam-Fourier transform Microwave (MB-FTMW) spectroscopy. Rotational spectra (up to J = 20) were recorded in the frequency region 4-19 GHz. Due to the internal rotation of the methyl group, some rotational transitions were split and the torsional barrier could be determined to V 3 (CH 3) = 1074.4(4) cm -1 . 
  Reference    Z. Naturforsch. 55a, 481—185 (2000); received February 9 2000 
  Published    2000 
  Keywords    Molecular Beam, Microwave Spectroscopy, Internal Rotation 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0481.pdf 
 Identifier    ZNA-2000-55a-0481 
 Volume    55 
4Author    S. Antolinez, J. L. Alonso, H. Dreizler, E. Hentrop, D. H. SutterRequires cookie*
 Title    Trifluoroacetic Acid; r 0 -Structure, Partial Substitution Structure and Deuterium Nuclear Quadrupole Coupling Studied by Molecular Beam Microwave Fourier Transform Spectroscopy and by ab initio Calculations  
 Abstract    We report the assignment and analysis of all stable monosubstituted isotopomers of trifluoroacetic acid. The 13 C and 18 0 isotopomers were observed in natural abundance. The rotational constants and quartic centrifugal constants are presented. The rotational constants are used to derive a partial substitution structure and a complete ro structure for future comparison with the corresponding values in hydrogen bridged bimolecules containing trifluoroacetic acid as a subunit. The deuterium nuclear quadrupole coupling constants are derived from the hfs-splittings of low-J rotational transitions of the CF 3 COOD isotopomer. The results of ab initio quantum chemical calculations are presented, which were carried out to assist in the assignment of the rotational spectra of the isotopomers and for comparison with the experimental molecular parameters. 
  Reference    Z. Naturforsch. 54a, 524—538 (1999); received August 3 1999 
  Published    1999 
  Keywords    Microwave Spectroscopy, Structure, D-hfs, Vibrational Averaging, ab initio Calculations 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0524.pdf 
 Identifier    ZNA-1999-54a-0524 
 Volume    54 
5Author    H. Zerbe-Foese, A. Guarnieri, O. L. StiefvaterRequires cookie*
 Title    Microwave and Millimeterwave Spectrum of 1,1-Difluoroethylene and the Vibrational Mode v 10 from FT-IR Spectroscopy  
 Abstract    Pure rotational spectra of 1,1-Difluoroethylene (1,1-DFE) in the vibrational ground state (GS) and in excited vibrational states (EVSs) have been investigated by double resonance modulation (DRM) microwave spectroscopy in the range from 12 GHz to 40 GHz, and by millimeterwave spectroscopy in the range from 90 to 260 GHz. In addition to the GS spectrum, rotational transitions have been observed for the EVSs v 10 = l, and 2, v 12 = l, v 6 = l, v n = l, v 4 = l, and v 9 = l. Along with other IR bands up to 1400cm" 1 , the fundamental vibrational band v 10 = l <-0 has been observed by FT-IR spectroscopy and has been analysed to yield v° 0 = 436.8851 cm -1 . Rotational constants and quartic distortion constants were deduced for all observed states. In addition, sextic distortion constants were obtained for the GS and for the EVSs v 10 = l, 2, v 6 = l, and v 12 = l by computer fits of combined microwave and millimeterwave data to Watson's A-re-duced Hamiltonian in I r representation. The S-reduced Hamiltonian in III r representation may be considered more appropriate for the calculation or the fitting of the transitions because 1,1-DFE is a near oblate asymmetric top. Thus, for comparison, results are given for both the A-and the S-reduction. 
  Reference    Z. Naturforsch. 51a, 53—62 (1996); received November 11 1995 
  Published    1996 
  Keywords    1, 1-Difluoroethylene, Molecular Spectroscopy, Microwave Spectroscopy, FT-IR Spec-troscopy, Excited Vibration States 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0053.pdf 
 Identifier    ZNA-1996-51a-0053 
 Volume    51