Spectrum of azulene. VI. Centrifugal distortion and the inertial defect

1969 ◽  
Vol 22 (1) ◽  
pp. 1 ◽  
Author(s):  
AJ McHugh ◽  
IG Ross
Keyword(s):  
Excited State ◽  
Low Frequency ◽  
Coupling Constants ◽  
Centrifugal Distortion ◽  
Vibrationally Excited ◽  
Normal Vibrations ◽  
Out Of Plane ◽  
Electronically Excited ◽  
Planar Molecules ◽  
Centrifugal Distortion Constants

The published microwave spectrum of azulene is re-analysed to yield the following values of the centrifugal distortion constants (units of kHz): Taaaa -1.45�0.76; Tbbbb -0.05�0.07; Taabb +0.70�0.42; Tabab -0.47�0.17. ��� The inertial defect Δ = Ic-Ia-Ib, typically positive in monocyclic compounds, is negative in azulene. According to the theory of Oka and Morino, the largest contribution to Δ is the vibrational part, which depends on the frequencies of the normal vibrations and on the Coriolis coupling constants. For the latter, a modified ?uniform coupling? approximation is proposed, based on sum rules applicable to planar molecules. Calculations are then carried out on pyridine, naphthalene, and azulene in which the change of sign of Δ, in two-ring, and presumably larger, aromatics is traced to the influence of low- frequency out-of-plane vibrations. For azulene, the values of Δ in a vibrationally excited state and an electronically excited state are also considered.

33S Nuclear Hyperfine Structure in the Rotational Spectrum of Thiazole

1993 ◽  
Vol 48 (12) ◽  
pp. 1219-1222 ◽  
Author(s):  
U. Kretschmer ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Hyperfine Structure ◽  
Molecular Beam ◽  
Microwave Spectroscopy ◽  
Coupling Constants ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Centrifugal Distortion Constants

Abstract We investigated the 33S nuclear quadrupole coupling of thiazole- 33S in natural abundance by molecular beam Fourier transform microwave spectroscopy. In addition the 14N nuclear quadrupole coupling could be analyzed with high precision. We derived the rotational constants A = 8529.29268 (70) MHz, B = 5427.47098 MHz, and C = 3315.21676 (26) MHz, quartic centrifugal distortion constants and the quadrupole coupling constants of 33S χaa = 7.1708 (61) MHz and χbb= -26.1749 (69) MHz and of 14N χ aa = -2.7411 (61) MHz and χbb = 0.0767 (69) MHz.

Preferred Rotameric Conformations of Isobutyraldehyde, Their Dipole Moments and Vibrationally Excited States by Microwave Spectroscopy

1986 ◽  
Vol 41 (3) ◽  
pp. 483-490 ◽  
Author(s):  
O. L. Stiefvater
Keyword(s):  
Oxygen Atom ◽  
Excited States ◽  
Ground State ◽  
Dipole Moments ◽  
Microwave Spectroscopy ◽  
Centrifugal Distortion ◽  
Gauche Conformation ◽  
Vibrationally Excited ◽  
Trans Conformation ◽  
Centrifugal Distortion Constants

The earlier prediction of the preferred and the less stable rotameric conformations of isobutyraldehyde, (CH3)2CHCHO, has been confirmed experimentally by microwave spectroscopy. The compound exists mainly in a gauche conformation, in which one of the methyl groups is eclipsed by the oxygen atom, and the less stable rotamer is the trans conformation, in which the oxygen atom eclipses the isopropyl hydrogen.Ground state rotational constants (in MHz) and centrifugal distortion constants (in kHz), together with dipole moments (in D), are:Rotation spectra due to three torsionally excited states of each rotamer have been identified, along with satellites arising from CH3 internal rotation and CC2 wagging.

Microwave Spectrum and Nuclear Quadrupole Coupling of 2-Chloropyridine

1987 ◽  
Vol 42 (2) ◽  
pp. 197-206 ◽  
Author(s):  
M. Meyer ◽  
U. Andresen ◽  
H. Dreizler
Keyword(s):  
Excited State ◽  
Ground State ◽  
Microwave Spectrum ◽  
Coupling Constants ◽  
Vibrationally Excited ◽  
Isotopic Species ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Mo Theory

The microwave spectrum of 2-chloropyridine, 2-Cl(C5H4N), has been studied to determine the 35Cl, 37Cl and 14N nuclear quadrupole coupling constants. The results are discussed within a simple MO theory. We propose an approximate r0-structure under certain assumptions. In addition to the ground state we observed one vibrationally excited state of both chlorine isotopic species of 2-chloropyridine.

scholarly journals Microwave Spectrum and Nuclear Quadrupole Interaction of 3-Bromothiophene in Excited Vibrational States

1983 ◽  
Vol 38 (12) ◽  
pp. 1309-1319 ◽  
Author(s):  
Yoshiaki Sasada
Keyword(s):  
Excited States ◽  
Nuclear Quadrupole Interaction ◽  
Coupling Constants ◽  
Vibrational Modes ◽  
Centrifugal Distortion ◽  
Vibrational States ◽  
Rotational Spectra ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Centrifugal Distortion Constants

Abstract The rotational spectra of 3-bromothiophene in the excited states of two vibrational modes were observed and the rotational constants, the centrifugal distortion constants, and the nuclear quadrupole coupling constants were determined. The wave numbers of the two vibrational modes were evaluated to be 210 cm-1 and 320 cm-1 by measuring relative intensities of the ground and excited vibrational transitions. Variations in the inertia defect for each of the vibrational modes are compared with the results of the approximate calculation.

Rotational Spectrum of Aminoborane: Centrifugal Distortion Constants and Boron and Nitrogen Hyperfine Structure

1991 ◽  
Vol 46 (9) ◽  
pp. 770-776 ◽  
Author(s):  
Kirsten Vormann ◽  
Helmut Dreizler ◽  
Jens Doose ◽  
Antonio Guarnieri
Keyword(s):  
Hyperfine Structure ◽  
Spin Rotation ◽  
Coupling Constants ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Rotational Spectra ◽  
Quadrupole Coupling ◽  
Wave Region ◽  
Nuclear Quadrupole ◽  
Centrifugal Distortion Constants

AbstractThe boron and nitrogen hyperfine structure in the rotational spectra of two aminoborane isotopomers, 11 BH2NH2 and 10BH2NH2, has been investigated and the quadrupole coupling constants of boron 10B, 11B and nitrogen 14N have been determined. We get the following results for the nuclear quadrupole coupling constants: χaa(11B) = -1.684 (14) MHz, χbb(11B) = -2.212 (11) MHz, χcc(11B) = 3.896(11) MHz, χaa(10B) = -3.481 (11) MHz, χbb(10B) = -4.623 (14) MHz, χCC(10B) = 8.104 (14) MHz and xaa(14N) = 0.095 (9) MHz, χbb(14N) = 2.091 (8) MHz, χcf4 (14N)=-2.186 (8) MHz. These nitrogen quadrupole coupling constants are those of the 11BH2 NH2 isotopomer. Additionally we were able to determine two out of the three spin rotation coupling constants caa, cbb, and ccc of boron, caa(11 B = 55.2 (26) kHz, cbb(11B) = 6.62 (36) kHz, caa (10B) = 15.26 (69) kHz and cbb(10B) = 4.94 (70) kHz. The spin rotation coupling constants ccc had to be fixed to zero in both cases. Furthermore we measured the rotational spectra in the mm-wave region to determine all quartic and several sextic centrifugal distortion constants according to Watson's A and S reduction

Mikrowellenspektrum, Rotationskonstanten, Kernquadrupolkopplungskonstanten und r0-Struktur von Äthylchlorsilan / Microwave Spectrum, Rotational Constants, Nuclear Quadrupol Coupling Constants and ro structure of Ethylchlorosilane

1974 ◽  
Vol 29 (7) ◽  
pp. 1081-1096 ◽  
Author(s):  
V. Typke ◽  
M. Dakkouri ◽  
W. Zeil
Keyword(s):  
Microwave Spectrum ◽  
Coupling Constants ◽  
Centrifugal Distortion ◽  
Trans Form ◽  
Rotational Constants ◽  
Bond Angles ◽  
Centrifugal Distortion Constants

The MW-spectra of trans- and gauche-rotamers of 5 isotopes of ethylchlorosilane have been measured and partially analyzed. From the analysis rotational constants, centrifugal distortion constants and nuclear quadrupol coupling constants have been obtained. The determination of the restructure from 30 rotational constants leads to different bond angles C -C -Si for the two conformers. The optimalization of the quadrupol coupling constants in the bond axis system on the basis of the r0-structure using all information on the 35Cl-species yields the following values: ZZZ = (-35.5±0.8) MHz, η = - 0.25±0.11 for the trans-form and ZZZ= (-36.3±2.7) MHz, η = -0.08±0.10 for the gauche-form.

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