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1.
The 2,3-13C2 isotopomer of butadiene was synthesized, and its fundamental vibrational fundamentals were assigned from a study of its infrared and Raman spectra aided with quantum chemical predictions of frequencies, intensities, and Raman depolarization ratios. For two C-type bands in the high-resolution (0.002 cm−1) infrared spectrum, the rotational structure was analyzed. These bands are for ν11 (au) at 907.17 cm−1 and for ν12 (au) at 523.37 cm−1. Ground state and upper state rotational constants were fitted to Watson-type Hamiltonians with a full quartic set of centrifugal distortion constants and two sextic ones. For the ground state, A0 = 1.3545088(7) cm−1, B0 = 0.1469404(1) cm−1, and C0 = 0.1325838(2)  cm−1. The small inertial defects of butadiene and two 13C2 isotopomers, as well as for five deuterium isotopomers as previously reported, confirm the planarity of the s-trans rotamer of butadiene.  相似文献   

2.
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 35Cl2 and 35Cl37Cl using the Watson A-reduced Hamiltonian model and Ir-representation. A ground-state combination difference analysis for the 35Cl37Cl isotopomer based on 1402 assigned transitions belonging to the ν6 band yields a band origin of 897.94493(10) cm−1 and values for the ground-state rotational constants: A0 = 1.7466454(44) cm−1, B0 = 0.05019643(82) cm−1 and C0 = 0.04877977(82) cm−1 together with quartic centrifugal distortion constants. The red-shift of 0.00444(10) cm−1 observed for the ν6 band origin of 35Cl37Cl relative to the 35Cl2 band origin is now consistent with the Rayleigh rule.  相似文献   

3.
The study of vibration resonance physics in propyne is based on experimental measurements of about 600 new rotational transitions between 495-590 and 700-760 GHz in excited vibrational levels v5 = 1, v8 = 1, v10 = 3 and v9 = v10 = 1 with vibrational energies around 1000 cm−1. The limits to the assignments and analysis were imposed by as yet unresolved anharmonic resonances with the states of the next higher polyad of levels lying above 1200 cm−1, which affect the rotational states involved in transitions that would be measurable with non-vanishing intensities. Vibration-rotation spectra pertaining to the levels in question were studied in the regions 880-1150 cm−1 (the ν5 and ν8 fundamental bands), 550-750 cm−1 (the v9 = v10 = 1 ← v10 = 1 hot bands) and 250-400 cm−1 (the v10 = 3 ← v10 = 2 “superhot” bands). A simultaneous least-squares fit of both types of data provides their reliable but in the case of accurate rotational data not always fully quantitative reproduction.  相似文献   

4.
The rotational spectra of the ground vibrational state and the ν9 = 1 torsional state have been reinvestigated and accurate spectroscopic constants have been determined. The torsional frequency, ν9 = 70(15) cm−1, has been determined by relative intensity measurements. The assignment of the infrared spectrum has been slightly revised and an accurate harmonic force field has been calculated. The equilibrium structure has been determined using different, complementary methods: experimental, semi-experimental and ab initio, leading to r(NN) = 1.870(2) Å, in particular.  相似文献   

5.
Rotationally resolved pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the 00, 61 and 41 vibrational levels of the ground electronic state of the formaldehyde cation were recorded using a resonant three-color three-photon excitation scheme. The first adiabatic ionization energy of CH2O (87793.33(1.30) cm−1) and the rigid-rotor rotational constants (A+ = 8.874(8) cm−1, B+ = 1.342(15) cm−1, C+ = 1.148(18) cm−1) of the vibronic ground state of CH2O+ were derived. A strong a-type Coriolis interaction between the 61 and 41 vibrational levels was observed. The Coriolis coupling parameter and the deperturbed fundamental vibrational frequencies of the in-plane-rocking mode ν6 and the out-of-plane bending mode ν4 were determined to be 8.70(10) cm−1, 823.67(30) cm−1 and 1036.50(30) cm−1, respectively. The intensity distribution of the photoelectron spectra was analyzed in the realm of a simple photoionization model.  相似文献   

6.
The infrared spectra of the 2ν1, 2ν2 and 2ν3 overtones of perchloryl fluoride, FClO3, have been recorded at high resolution using monoisotopic pure samples. Four symmetric top species have been investigated: F35Cl16O3, F37Cl16O3, F35Cl18O3 and F37Cl18O3. The vi = 2, i = 1, 2, 3 vibrationally excited states are totally symmetric, so these overtones correspond to parallel bands of medium/weak intensity, centered from 2010 to 2120 cm−1 (2ν1), from 1390 to 1430 cm−1 (2ν2) and from 1070 to 1100 cm−1 (2ν3). Most of the bands are unperturbed and their analysis was straightforward. The band origins, the rotational and centrifugal molecular constants in the v1 = 2, v2 = 2 and v3 = 2 states have been determined, with standard deviations of the fits from 0.00024 to 0.00067 cm−1. The 2ν1 overtones of F35Cl16O3 and F37Cl16O3 are perturbed by an A1/E Coriolis resonance between the v1 = 2 state and one E component of the v4 = 1, v6 = 2 manifold. The 2ν2 of F37Cl18O3 is perturbed by the same kind of interaction involving the v1 = v6 = 1 (E) state, at about 1396 cm−1. In these bands the resonance is localized on rotational levels with specific J and K values. As a consequence, a few transitions of the perpendicular bands involving the interacting levels could be identified in the spectra. A simultaneous fit of the transitions assigned to the dyads has been performed and the parameters of the excited states have been determined, including the high order Coriolis interaction coefficient . The anharmonic constants x11, x22, x33 of all the studied isotopologues of FClO3, x46 of F35Cl16O3, x46 + g46 of F37Cl16O3 and x16 of F37Cl18O3, have been derived.  相似文献   

7.
Assignments of the vibrational fundamentals of cis- and trans-1,3,5-hexatriene are reevaluated with new infrared and Raman spectra and with quantum chemical predictions of intensities and anharmonic frequencies. The rotational structure is analyzed in the high-resolution (0.0013-0.0018 cm−1) infrared spectra of three C-type bands of the trans isomer and two C-type bands of the cis isomer. The bands for the trans isomer are at 1010.96 cm−1 (ν14), 900.908 cm−1 (ν16), and 683.46 cm−1 (ν17). Ground state (GS) rotational constants have been fitted to the combined ground state combination differences (GSCDs) for the three bands of the trans isomer. The bands for the cis isomer are at 907.70 cm−1 (ν33) and 587.89 cm−1 (ν35). GS rotational constants have been fitted to the combined GSCDs for the two bands of the cis isomer and compared with those obtained from microwave spectroscopy. Small inertial defects in the GSs confirm that both molecules are planar. Upper state rotational constants were fitted for all five bands.  相似文献   

8.
Two new bands, 2ν1+ν2+ν3+2ν5 and 5ν3 with origin at 12220.692 and 12496.158 cm−1, respectively, were identified on new FT-ICLAS spectra of 12C2HD and rotationally analyzed. The rotational analysis of two known bands, with origin at 12038.538 and 12234.872 cm−1 was extended. Another band, 2ν1+2ν5 with origin at 7843.6622 cm−1, was identified for the first time and rotationally analyzed, from a high pressure conventional FT spectrum. Some 115 known vibrational state energies in the molecule, extending up to the visible range, were used to produce updated vibrational constants. Both a straightforward Dunham model and a global model accounting for a single anharmonic resonance, K1/255, were used. The results are discussed.  相似文献   

9.
The spectroscopic knowledge of sulfur hexafluoride, which is necessary for a correct remote sensing and monitoring of this species in the Earth’s atmosphere, is still very partial. In particular, the hot bands in the strongly absorbing ν3 region (near 948 cm−1) have not been analyzed yet. Their study implies the analysis of many vibrational levels and thus the spectroscopy of various fundamental, harmonic, and combination bands. The present work is a new contribution to this topic, concerning the ν2+ν4 combination band. The FTIR spectrum of this region has been recorded at room temperature with a resolution of 0.002 cm −1. The data have been analyzed thanks to the HTDS software (http://www.u-bourgogne.fr/LPUB/shTDS.html) developed in Dijon for XY6 octahedral molecules. Seven hundred and fifty-nine lines could be assigned up to J=112, and the standard deviation is 0.0022 cm−1. The distance between the two vibrational sublevels with respective symmetry F1u and F2u is 0.348 cm−1.  相似文献   

10.
The high-resolution infrared spectrum of the polar N2O dimer has been observed in the region of the N2O ν3 fundamental (∼1280 cm−1) using a tunable diode laser to probe a pulsed supersonic slit jet. About 120 rotational transitions were assigned in terms of an a/b hybrid band of a planar asymmetric top molecule with a slipped parallel structure. The vibrational origin was determined to be 1290.21 cm−1, showing a blue shift of 5.31 cm−1 with respect to the monomer band origin. In addition, the spectrum of the nonpolar isomer at 1279.71 cm−1 has been remeasured and analyzed in improved detail. Small but widespread perturbations are noted in this band, which appear somewhat similar to larger effects observed previously in the ν1 + ν3 region for nonpolar (N2O)2.  相似文献   

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