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Rotational spectra of the quasi-spherical symmetric molecules, 16OPF3 and PH3, are analyzed with all the data currently available. In both cases the current formulation that uses rotational contact transformations to completely diagonalize the ground state energy matrix appears to be inadequate, due to the smallness of the quantity |;A0 ? B0|. This quantity represents only 5% of A0 or B0 in the case of OPF3 and 11% in the case of PH3. Thus, both analyses require the resonance terms in ΔK = ±3 and/or ΔK = ±6 to be taken into account through diagonalization of the energy matrix. The ground state parameters as well as the ground state energies are given for both molecules.  相似文献   

4.
Eight P-branch transitions from the ν5141 difference band of C2D2 have been observed in the microwave region. Significant improvements in the spectroscopic constants for the two states involved in the difference band have been obtained by combining infrared and microwave data. The Stark shifts for the observed C2D2 lines are discussed in some detail. The vibrational transition moment is found to be μvib = 0.0358 ± 0.0020 D.  相似文献   

5.
A tensorial formalism adapted to the case of quasi-spherical XY2Z2 asymmetric tops such as SO2F2 has been developed as an extension of the usual one for the tetrahedral molecules. We use the O(3)⊃TdC2v group chain. All the coupling coefficients and formulas for the computation of matrix elements are given for this chain. Such relations are then deduced in the C2v group itself. We also present a development of the Hamiltonian, dipole moment, and polarizability operators for the molecules under consideration using this formalism. These operators are involved in the calculation of the energies and intensities of rovibrational transitions and are essential for spectrum simulations. Expressions for the matrix elements are derived for these operators. A first application to the ground state of SO2F2 is presented. Programs for spectrum simulation and fit using these methods are freely available at the URL http://www.u-bourgogne.fr/LPUB/c2vTDS.html.  相似文献   

6.
A tensorial formalism adapted to the case of XY3Z symmetric tops has been developed. We use the O (3) ⊃ Cv ⊃ C3v group chain. All the coupling coefficients and formulas for the computation of the matrix elements are given for this chain. Such relations are also deduced in C3v group itself.  相似文献   

7.
The interaction of vibration and rotation is considered in the computation of the intensities of rotational lines in the first overtone bands of axially symmetric molecules of the group C3v. The calculation utilizes the contact transformation method through first order of approximation as outlines by Hanson and Nielsen. General formulas for the intensities of the lines in the first overtone bands 2νn and 2νm are obtained, where n and m denote normal modes of species A1 and E, respectively. It is found that to this order of approximation the usual selection rules ΔJ = 0, ±1 and ΔK = 0 are observed for the parallel overtone band 2νn. For the overtone band 2νm, the selection rules are more complicated, being ΔJ = 0, ±1; Δlm = 0 and ΔK = 0, Δlm = ±2 and ΔK = ?1, or Δlm = ±2 and ΔK = ±2.  相似文献   

8.
Eight emission spectra of pure N2O and N2O + N2 + He mixtures excited by a radio frequency discharge were recorded by Fourier Transform Spectroscopy at a resolution of 0.005 and 0.004 cm−1 in the 4.5 μm region. Results (wavenumbers, band centers, and spectroscopic constants) concerning nine new vibrational transitions which have not been observed before, and which occur between highly excited levels of the bending mode are reported. The derived spectroscopic parameters allow us to reproduce the experimental wavenumbers with an RMS error lower than 4.5 × 10−4 cm−1.  相似文献   

9.
The spectral line strengths in the v2 band of H2CO (segments spanning 1720-) have been determined relative to two sets of spectral line groups in the v1 and v5 band, using tunable diode laser spectroscopy. Simultaneous detection using a dual-diode instrument with a absorption cell was employed to assure identical H2CO column density for the two spectral regions. The results in the selected regions of this study are in good agreement with the line positions and the relative intensities specified in an unpublished complete line listing for the v2 band prepared by Linda Brown (see full text for reference). Based upon measurements of individual groups of spectral lines in the P, Q and R branches, the absolute band strength has been determined to be .  相似文献   

10.
The infrared spectrum of CF2Cl2 has been measured under medium resolution in the range 1600-400 cm?1. More than 100 bands including fundamental, overtone, combination, and “hot” bands of the three isotopic species CF235Cl2, CF235Cl37Cl, and CF237Cl2 have been identified. The band contour studies have enabled the fundamental vibrations to be unambiguously assigned, including the modes ν3 and ν7, the positions of which were previously in doubt. The observed values for CF235Cl2 in conjunction with the frequency shift data for CF235Cl37Cl and CF237Cl2 have been used in determining a general valence force field, which adequately describes the system investigated. A Fermi resonance interaction between ν8 and ν3 + ν9 levels for the three isotopic species has been interpreted. The corresponding perturbations between those levels obtained by adding ν2 or ν5 to both ν8 and ν3 + ν9 have also been found and the related features carefully investigated.  相似文献   

11.
Measurements are reported for the rotational spectrum of the C4v molecule IOF5 in the ground vibrational state in the range 30–75 GHz (J7 ← 6 to J17 ← 16). The K-doubling of |k| = 2 transitions due to an off-diagonal centrifugal distortion interaction of the type (Δl, Δk) = (0, ±4) has been observed. The centrifugal distortion constants DJ, DJK, and R6 have been determined as 0.139(2) kHz, 0.107(4) kHz, and 21(2) Hz, respectively.  相似文献   

12.
General algebraic expressions for the vibration-rotation energy levels and the associated rotational transitions of C3v symmetric top molecules are developed. These expressions are presented in a convenient form for analysing the spectra of a molecule with any degree of excitation of a degenerate vibrational mode and have been applied to the spectrum of CH3C15N.  相似文献   

13.
An expression for the kinetic energy part of the vibration-torsion-rotation Hamiltonian of an asymmetric top molecule containing a C3v internal rotor has been derived. The terms for various interactions in the molecule, viz. Coriolis interaction between rotation (both overall and internal rotation) and vibration, centrifugal distortion and anharmonicity of molecular vibrations induced by the internal, and overall rotation of the molecule, have been formulated. For a planar molecule with Cs symmetry we have obtained the vibrationally averaged rotation-internal rotation Hamiltonian. Diagonalization of this Hamiltonian for a particular vibrational state will yield the rotation-internal rotation energy levels and hence the transition frequencies. These data will be useful for analysis of high-resolution infrared spectra obtained by laser or Fourier transform spectroscopy of nonrigid molecules with internal rotor. We also present a set of quartic centrifugal distortion coefficients associated with rotation and internal rotation. These data will be helpful for evaluation of vibrational potential constants of the orthorhombic asymmetric top molecules.  相似文献   

14.
The reduction of the effective Hamiltonian has been derived for C3v symmetric top molecules in the vtequals;1 state with extension to nuclear quadrupole coupling. The theory has been applied to the hyperfine structures of rotational transitions observed for AsF3 (v4equals;1) [H. Bürger, J. Demaison, P. Dréan, C. Gerke, L. Halonen, H. Harder, H. Mäder, J. Radtke, and H. Ruland, J. Mol. Spectrosc.180, 85-99 (1996)]. The data have been analyzed using two reduced forms of the effective Hamiltonian which follow the reductions Q and D [E. I. Lobodenko, O. N. Sulakshina, V. I. Perevalov, and Vl. G. Tyuterev, J. Mol. Spectrosc.126, 159-170 (1987)] in the pure rovibrational case. The unitary equivalence of the derived parameter sets has been demonstrated.  相似文献   

15.
The vibration-rotation spectrum of 13C2D2 has been recorded in the infrared region between 420 and 1100 cm−1 with an effective resolution ranging from 0.004 to 0.006 cm−1, and in the millimeter-wave region between 68 and 518 GHz. A total of about 1400 rovibrational transitions (66 of which have been measured in the millimeter-wave region) have been assigned to 8 bands with 15 l-vibrational components involving the bending states up to vt=v4+v5=2. The ground state and nine vibrationally excited states have been characterized. All the measured transitions have been analyzed simultaneously by adopting a model Hamiltonian which takes into account the usual vibration and rotation l-type resonances, together with the Darling-Dennison coupling between the v4=2 and v5=2 bending states. The derived spectroscopic parameters reproduce the transition wavenumbers with a standard deviation of the fit of the order of the experimental uncertainty.  相似文献   

16.
The vibration-rotation spectra of 13C monosubstituted acetylene, 12C13CH2, have been recorded in the region between 450 and 3200 cm−1 with an effective resolution ranging from 0.004 to 0.006 cm−1. A total of about 5300 rovibrational transitions have been assigned to 53 bands involving the bending states up to vt=v4+v5=4, allowing the characterization of the ground state and of 30 vibrationally excited states. All the bands involving states up to vt=3 have been analyzed simultaneously by adopting a model Hamiltonian which takes into account the vibration and rotation l-type resonances. The derived spectroscopic parameters reproduce the transition wavenumbers with a RMS value of the order of the experimental uncertainty. Using the same model larger discrepancies between observed and calculated values have been obtained for transitions involving states with vt=4. These could be satisfactorily reproduced by only adopting, in addition to the previously determined parameters which were constrained in the analysis, a set of effective constants for each vibrational manifold.  相似文献   

17.
The and fundamental bands of CH379Br and CH381Br have been studied by Fourier transform infrared spectroscopy with an unapodized resolution of 0.004 cm−1, corresponding to an improvement of one order of magnitude compared to previous studies. For both isotopomers, some 2427 (2239) lines were newly assigned for the parallel and the perpendicular bands and, in addition, 80 perturbation-allowed transitions were also added. The ground-state axial rotational constants A0 were redetermined from allowed and perturbation-allowed infrared transitions observed in the v2 and v5 bands around the local crossing. The A0 values obtained for both isotopomers are more accurate but fully compatible with those obtained previously. Using those results, and the variation of the rotational constants with vibration, new accurate equilibrium constants Ae and Be have been also determined for CH379Br and CH381Br. The excited states v2=1 and v5=1 are coupled by Coriolis-type interactions (Δl=±1,ΔK=±1) and (Δl=?1,ΔK=±2), while the l5=±1 levels of v5 interact also through “l(2,2)”-type interaction (Δl=±2,ΔK=±2). The Coriolis coupling term was determined to be for CH379Br and for CH381Br. All interaction parameters have been determined with higher accuracy, compared to previous studies. A total of 4213 (3704) line positions with J?68(64) and K?16(11) including all available data was fitted using 20 (18) parameters with a root-mean-square deviation of 0.0007 (0.0006) cm−1 for CH379Br and CH381Br, respectively. Two different but equivalent forms of reduced Hamiltonians with two different sets of constrained constants were successfully applied according to Lobodenko's reduction [J. Mol. Spectrosc. 126 (1987) 159]. The ratio of the transition moments, |d2/d5|=1.65, and a positive sign of the Coriolis intensity perturbation d2×ζ25×d5 were determined. Therefore, it has been possible to generate an accurate prediction of the whole spectrum between 1200 and 1650 cm−1, including Q branches.  相似文献   

18.
Anomalies in the microwave spectrum of CF3CN in the state v8 = 1 have been completely resolved by a diagonalization treatment of the matrix elements 〈l, K|l ± 2, K ± 2〉. Effects other than l-type resonance are thereby ruled out. Computation was greatly facilitated by a convenient factorization of the energy matrix which makes the method readily applicable to a large number of problems in vibration-rotation analysis. The general applicability of the method to higher vibrationally excited states was illustrated by a successful treatment of the microwave spectrum in the state v8 = 2.  相似文献   

19.
Emission spectra of gaseous mixtures involving isotopic species of CO2 excited by a dc discharge were recorded under Doppler-limited resolution, using a high-information Fourier Transform Interferometer, in the region 4–5 μm. In this paper are given the results concerning 34 vibrational transitions (Δv3 = 1), for 12C18O2. The band centers and the spectroscopic constants for the 39 vibrational levels involved are reported. They reproduce more than 1000 experimental wavenumbers with a RMS of the order of 2 × 10?5 cm?1 for the best vibrational transition and less than 3 × 10?4 cm?1 for most of the others. From a weighted simultaneous fit of all the experimental wavenumbers belonging to the Σ-Σ transitions, a set of molecular parameters was computed. A good reproduction of the experimental wavenumbers was obtained for all the vibrational transitions except those involving the level v3 = 9, our conclusion being that a local vibrational perturbation exists for this level.  相似文献   

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