| 1. |
- Hegelund, F, et al.
(författare)
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The high-resolution infrared spectrum of isoxazole vapor between 800 and 1700 cm(-1)
- 2005
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Ingår i: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852. ; 229:2, s. 244-256
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Tidskriftsartikel (refereegranskat)abstract
- The Fourier transform gas-phase IR spectrum of isoxazole, C3H3NO, between 550 and 1700 cm(-1) was measured with a resolution of ca. 0.003 cm(-1). Ten fundamental bands in the region 800-1700 cm(-1) have been analyzed by the Watson Hamiltonian model to yield upper state spectroscopic constants. A number of local resonances have been identified in the bands and explained qualitatively, and the unobserved nu(14)(A") fundamental band has been located at 897.5(5) cm(-1) from its perturbation effects on the neighboring fundamentals.
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| 2. |
- Hegelund, F, et al.
(författare)
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The infrared spectrum of isothiazole in the range 600-1500 cm(-1), including a high-resolution study of the v(11)(A ') band at 818cm(-1) and the v(16)(A '') band at 727cm(-1), together with ab initio studies of the full spectrum
- 2004
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Ingår i: Molecular Physics. - : Informa UK Limited. - 1362-3028 .- 0026-8976. ; 102:14-15, s. 1583-1595
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Tidskriftsartikel (refereegranskat)abstract
- The gas-phase high-resolution infrared spectrum of isothiazole in the range 600-1500 cm(-1) has been recorded, and revised band centres obtained for a number of vibrations. An analysis of the nu(11)(A') band at 818 cm(-1) and the nu(16)(A") band at 727cm(-1) has been performed, using the Watson Hamiltonian, A-reduction, IIIr representation. These were combined with previous microwave spectral data to provide combined analyses for rotational constants and quartic centrifugal distortion constants Delta(J), Delta(JK), Delta(K), delta(J) and delta(K). These extend the knowledge derived from previous microwave and IR spectral studies. The equilibrium structures and the derived harmonic frequencies were calculated by ab initio methods, using a variety of basis sets with MP2, MP4 and CCSD(T) methods, and a comparison of these with experimental data is discussed. At a pragmatic level, the closest correlation of the rotational constants with experiment is not obtained with the most sophisticated methodology. Similarly, the vibration frequencies and intensities also vary strongly with the procedure. In particular, we found that the cc-pVTZ + MP2 results probably provide the best numerical comparison with experimental IR data for this molecule.
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| 3. |
- Wugt Larsen, René, et al.
(författare)
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The equilibrium structure of trans-glyoxal from experimental rotational constants and calculated vibration-rotation interaction constants
- 2003
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084. ; 5:22, s. 5031-5037
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Tidskriftsartikel (refereegranskat)abstract
- A total of six high-resolution FT-IR spectra for trans-glyoxal-d(2), trans-glyoxal-d(1) and trans-glyoxal-C-13(2) were recorded with a resolution ranging from 0.003 to 0.004 cm(-1). By means of a simultaneous ground state combination difference analysis for each of these isotopologues using the Watson Hamiltonian in A-reduction and I-r-representation the ground state rotational constants are obtained. An empirical equilibrium structure is determined for trans-glyoxal using these experimental ground state rotational constants and vibration - rotation interaction constants calculated at the CCSD(T)/cc-pVTZ level of theory. The least-squares fit yields the following structural parameters for trans-glyoxal: r(e)(C-C) = 1.51453(38) Angstrom, r(e)(C-H) = 1.10071(26) Angstrom, re(C= O) = 1.20450(27) Angstrom, alpha(e)(CCH) = 115.251(24) degrees, and alpha(e)(HCO) = 123.472(19)degrees in excellent agreement with theoretical predictions at the CCSD(T)/cc-pVQZ level of theory.
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| 4. |
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| 5. |
- Hegelund, F, et al.
(författare)
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High-Resolution Infrared and Microwave Study of the n20 and n21 Levels near 300 cm-1 in 1,2,4-Triazine.
- 2003
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Ingår i: Journal of Molecular Spectroscopy. - 0022-2852. ; 217:1, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- The gas phase far-IR spectrum of the small nu, Greek20 (A″, 367.88 cm−1) and small nu, Greek21 (A″, 311.28 cm−1) bands of 1,2,4-triazine, a five membered ring having the point group Cs, has been studied at a resolution ranging from 0.002 to 0.003 cm−1. From the MW spectrum 58 transitions in the small nu, Greek20 level and 64 in the small nu, Greek21 level have been assigned. The small nu, Greek20 and small nu, Greek21 modes which are due to non-planar motions of the ring system are found to be nearly unperturbed. From a simultaneous analysis of IR and MW transitions band centers, rotational constants, and the quartic centrifugal distortion constants ΔJ, ΔJK, ΔK, small delta, GreekJ, and small delta, GreekK have been obtained using the Watson Hamiltonian, A-reduction, IIIr-representation.
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| 6. |
- Larsen, R. Wugt, et al.
(författare)
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High-resolution infrared study of collisionally cooled trans-1,2-dichloroethylene
- 2007
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Ingår i: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852. ; 243:1, s. 99-102
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Tidskriftsartikel (refereegranskat)abstract
- A recently constructed long-path enclosive flow cooling apparatus is employed to obtain the Fourier transform gas-phase infrared absorption spectrum of natural isotopic trans-1,2-dichloroethylene with a resolution of 0.00190 cm(-1) in the 800-1000 cm(-1) spectral region. The rotational structure of the out-of-plane CH flapping fundamental has been analyzed for the isotopic analogues Cl-35(2) and (ClCl)-Cl-35-Cl-37 using the Watson A-reduced Hamiltonian model and I-r-representation. A ground-state combination difference analysis for the (ClCl)-Cl-35-Cl-37 isotopomer based on 1402 assigned transitions belonging to the v(6) band yields a band origin of 897.94493(10) cm(-1) and values for the ground-state rotational constants: A(0) = 1.7466454(44) cm(-1), B-0 = 0.05019643(82) cm(-1) and C-0 = 0.04877977(82) cm(-1) together with quartic centrifugal distortion constants. The red-shift of 0.00444(10) cm(-1) observed for the v(6) band origin of (ClCl)-Cl-35-Cl-37 relative to the Cl-35(2), band origin is now consistent with the Rayleigh rule. (c) 2007 Elsevier Inc. All rights reserved.
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| 7. |
- Nissen, S, et al.
(författare)
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High-resolution infrared study of the nu(11) band of allene
- 2002
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Ingår i: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852. ; 216:2, s. 197-202
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Tidskriftsartikel (refereegranskat)abstract
- The high-resolution infrared spectrum of allene has been observed in the 280-380 cm(-1) region at a nominal resolution of 0.00125 cm(-1) using the IR beamline at the MAX-1 electron storage ring in Lund. The spectrum shows the bending fundamental of the nu(11) band from which spectroscopic constants for the nu(11) level have been obtained. The accompanying hot band component 2nu(11)(2)-nu(11)(1) has also been assigned and analyzed.
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| 8. |
- Palmer, MH, et al.
(författare)
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The infrared spectrum of isoxazole in the range 600-1400 cm(-1), including a high-resolution study of the v(7)(A ') band at 1370.9cm(-1) and the v(16)(A '') band at 764.9cm(-1), together with ab initio studies of the full spectrum
- 2004
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Ingår i: Molecular Physics. - : Informa UK Limited. - 1362-3028 .- 0026-8976. ; 102:14-15, s. 1569-1581
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Tidskriftsartikel (refereegranskat)abstract
- The high resolution infrared gas phase spectrum of isoxazole in the range 600-1400 cm(-1) has been recorded and more precise centres obtained for a number of bands; analyses of the nu(7)(A') band at 1370.9 cm(-1) and the nu(16)(A") band at 764.9 cm(-1) have been performed. Use of the Watson Hamiltonian, A-reduction, IIIr-representation and simultaneous analysis of the present IR and previous microwave data, has led to rotation constants and quartic centrifugal distortion constants Delta(J), Delta(JK), Delta(K), delta(J) and delta(K) for the ground state and for the nu(16) vibrationally excited states. The equilibrium structures and the derived harmonic frequencies have been calculated by ab initio methods using triple zeta + polarization (TZVP) and cc-pVTZ basis sets, with MP2, MP4 and CCSD(T) methods. At each methodology, for closest numerical agreement between the calculated and observed rotation constants, the optimum basis set seems to be TZVP rather than cc-pVTZ basis sets. However, the order of the highest A" and lowest A' symmetry vibrations is only resolved by the cc-pVTZ basis set with the MP4 methodology, which does generate the experimental sequence (nu(14)>nu(13)). The CCSD(T) methodology does not lead to significant difference over either MP2 or MP4 with the TZVP basis set.
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| 9. |
- Sablinskas, V, et al.
(författare)
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A high-resolution FT-IR study of the fundamental bands v(7), v(8), and v(18) of ethene secondary ozonide
- 2005
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 109:39, s. 8719-8723
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Tidskriftsartikel (refereegranskat)abstract
- Ozonization reaction of ethene in neat film at 77 K was performed. Separation of ethene secondary ozonide from the other products of the reaction was performed by continuous pumping of the reactor. Only the products, which evaporated from the walls of the reactor at 185 K, were transferred to the gas cell. The high-resolution infrared absorption spectrum of gaseous ethene secondary ozonide (C2H4O3) in a static gas long-path absorption cell has been recorded in the 900-1100 cm(-1) spectral region at 185 K. The spectral resolution was 0.003 cm(-1). Analyses of the nu(7)(A) band at 1037.0 cm(-1), the nu(8)(A) band at 956.1 cm(-1), and the nu(18)(B) band at 1082.1 cm(-1) have been performed using the Watson Hamiltonian model (A, reduction; IIIr, representation). A set of ground-state rotational and quartic centrifugal distortion constants have been obtained, and upper state spectroscopic constants have been determined for the bands investigated. A local resonance observed in vis is explained as c-Coriolis interaction with nu(10) + nu(11).
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| 10. |
- Wugt Larsen, René, et al.
(författare)
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A high-resolution FT-IR study of the fundamental bands nu(6), nu(10), and nu(11) of trans-glyoxal
- 2002
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Ingår i: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852. ; 211:1, s. 127-134
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Tidskriftsartikel (refereegranskat)abstract
- The high-resolution Fourier transform infrared spectrum of trans-glyoxal in the gas phase has been recorded in the spectral regions 700-900 cm(-1), 1200-1400 cm(-1), and 1600-1800 cm(-1) with a resolution ranging from 0.0020 to 0.0025 cm(-1). The spectrum displays extensive rotational structures which are assigned to the three fundamental bands upsilon(6) (A(u), 801.5 cm(-1)), upsilon(10) (B-u, 1732.1 cm(-1)), and upsilon(11) (B-u, 1312.5 cm(-1)). A total of ca. 5000 absorption lines have been assigned to these three bands. A simultaneous ground state combination difference analysis of all three bands yields improved ground state spectroscopic constants for trans-glyoxal. Furthermore, a number of spectroscopic constants for the nu(6) and nu(11) levels have been determined for the first time.
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