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- Perrin, A., et al.
(författare)
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Microwave and submillimeter-wave measurements of (HDCO)-C-12-O-16 in the nu(4), nu(5), and nu(6) bands : Evidence of vibrational induced rotational axis switching ("VIRAS")
- 2002
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Ingår i: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852 .- 1096-083X. ; 216:2, s. 214-224
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Tidskriftsartikel (refereegranskat)abstract
- The rotational spectrum of HDCO in the 4(1),5(1), and 6(1) excited vibrational states has been investigated in Lille and Kiel using a sample enriched in deuterium. In Lille, the measurements were performed in the millimeter region (100-600 GHz). The spectra in Kiel were recorded using Fourier transform microwave spectrometers in the regions around 8-18 and 18-20 GHz. employing a rectangular waveguide of length 12 m and a circular waveguide of length 36 m, respectively, These results Acre combined with the 4(1), 5(1), and 6(1) infrared energy levels which were obtained front a previous analysis of FTS spectra of the v(4) (CHD bend), v(5) (CHD rocking). and v(6) bands (out of plane bend) recorded in the 10-mum region at Giessen (A. Perrin, J,-M, Flaud, M. Smirnov, and M. Lock, J. Mol. Spectrosc. 203, 175-187 (2000)). The energy level calculation of the 4(1). 5(1), and 6(1) interacting states accounts for the usual A- and B-type Coriolis resonances in the 5(1) double left right arrow 6(1) and 4(1) double left right arrow 6(1) off diagonals blocks. In addition since the energy levels of the 5(1) and 6(1) states are very strongly resonating, it proved necessary. as ill our previous study. to Use a {J(x), J(z)} nonorthorhombic term in the 5(1) and 6(1) v-diagonal blocks of the Hamiltonian matrix in order to reproduce properly file observed microwave transitions and infrared energy levels. Therefore, this work confirms that HDCO is a good example of the vibrational induced rotational axis switching ("VIRAS") effect.
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| 2. |
- Wörmke, Stephan, et al.
(författare)
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A molecular beam Fourier transform microwave study of 2-methylpyridine and its complex with argon : structure, methyl internal rotation and N-14 nuclear quadrupole coupling
- 2004
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Ingår i: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 102:14-15, s. 1625-1639
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Tidskriftsartikel (refereegranskat)abstract
- The rotational spectrum of 2-methylpyridine (alpha-picoline, CH3C5H4N) in the two lowest levels of methyl internal rotation (m = 0, +/-1) has been recorded in the frequency range from 2 to 15 GHz using a molecular beam Fourier transform microwave spectrometer. The high resolution and sensitivity of this spectroscopic technique allowed resolution of hyperfine structures due to N-14 nuclear quadrupole coupling with high accuracy and detection of the spectra of the N-15- and all C-13-isotopomers. These investigations considerably extend the results from an earlier study on the normal species (DREIZLER, H., RUDOLPH, H. D., and MADER, H., 1970, Z. Naturforsch., 25a, 25); improved rotational and centrifugal distortion constants as well as all components of the N-14 quadrupole coupling tensor have been obtained. Analysis of the spectra of the isotopomers yielded the N-14 quadrupole coupling constants X,c and chi(aa) - chi(bb) (for the C-13 species), the potential parameter V-3 for the barrier hindering the internal rotation of the methyl group, and, in particular, r(o), r(s), r(m)((1)) and r(m)((2)) structural parameters for the molecule. In addition to the microwave studies on the monomer, we have also investigated the rotational spectrum of the weakly bound dimer of normal 2-methylpyridine with Ar. The results obtained for the quadrupole coupling constants and the hindering potential for the internal methyl rotation show that the corresponding parameters are not significantly, or only slightly, changed in the complex.
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