共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Baldacci A. Pietropolli Charmet G. Cazzoli C. Puzzarini 《Journal of Molecular Spectroscopy》2007,246(1):126-132
The enriched 81Br isotopic species of bromofluoromethane has been investigated in the infrared and microwave regions. The rovibrational spectrum of the ν5 fundamental has been studied by high resolution FTIR spectroscopy, while the rotational spectra of the ground and v6 = 1 states have been observed by means of microwave spectroscopy. More than 2700 transitions have been assigned in the ν5 band and the analysis of the rovibrational structure reveals a first-order c-type Coriolis resonance with the v6 = 2 state. The present study improves the ground state constants available in the literature and enables the determination of further centrifugal distortion parameters together with the full bromine quadrupole coupling tensor. A set of spectroscopic parameters up to the sextic distortion terms for the vibrational excited states has been accurately evaluated for the first time. 相似文献
2.
Born-Oppenheimer breakdown effects and hyperfine structure in the rotational spectra of SbF and SbCl
Stephen A. Cooke 《Journal of Molecular Spectroscopy》2005,234(2):195-203
Pure rotational spectra have been measured for the ground electronic states of SbF and SbCl. The molecules were prepared by laser ablation of Sb metal in the presence of SF6 or Cl2, respectively. Their spectra were measured with a cavity pulsed jet Fourier transform microwave spectrometer. Although both molecules have two unpaired electrons, they are subject to Hund’s coupling case (c), and have X10+ ground states. The spectra have been interpreted with the formalism of 1Σ+ molecules. For both molecules spectra of several isotopomers have been measured in the ground and first excited vibrational states. Large hyperfine splittings attributable to both nuclear quadrupole coupling and nuclear spin-rotation coupling have been observed. A Dunham-type analysis has produced unusually large Born-Oppenheimer breakdown parameters, which are interpreted in terms of the electronic structures of the molecules. 相似文献
3.
《Journal of Molecular Spectroscopy》1984,104(1):183-193
The high-resolution microwave spectra of the79Br and81Br isotopic species of cyclohexyl bromide, C6H11Br, have been assigned for the equatorial and axial isomers, respectively. The ground-state energy of the axial isomer is 0.72 ± 0.30 kcal/mole higher than that of the equatorial one. The quadrupole coupling constants have been obtained for the equatorial and axial ground states of both the isotopes. Several vibrational excited states of the equatorial and axial conformers (79Br) have also been analyzed. 相似文献
4.
Helen O. Leung Mark D. Marshall Andrew L. Vasta 《Journal of Molecular Spectroscopy》2009,253(2):116-10980
The rotational spectra of eight isotopomers of 1-chloro-1-fluoroethylene in the 6-22 GHz region have been collected and analyzed. Each rotational transition is split into hyperfine components by the chlorine (either 35Cl or 37Cl) nuclear quadrupole coupling interaction and additionally, one or more smaller interactions such as the spin-rotation interaction due to the fluorine atom, hydrogen-hydrogen spin-spin coupling interactions, and in appropriately substituted species, the deuterium nuclear quadrupole hyperfine interaction. The rotational constants derived from these isotopomers allow the determination of average and Kraitchman substitution structures for 1-chloro-1-fluoroethylene, whereas the availability of the diagonal chlorine nuclear quadrupole coupling constants for all the isotopomers provides complete quadrupole coupling tensors for both 35Cl and 37Cl. In the course of this work, the rotational spectrum of an excited vibrational state of the normal isotopomer was observed, which ab initio calculations suggest should be assigned to ν9=1, an in-plane bending motion at the CFCl end of the molecule. 相似文献
5.
The microwave spectrum of chloromethyl methyl ether has been studied in the region 12.4–40 GHz. For 35Cl species, a- and c-type transitions have been assigned for the ground state, the first excited state of the chloromethyl torsional mode, and the first excited state of the methyl torsional mode. Assignments were also made for the ground state of 37Cl species. The assigned transitions are due to the gauche conformer. The nuclear quadrupole coupling constants were determined for the ground state of 35Cl and 37Cl species. The observed A-E splittings of the rotational transitions arising from the three vibrational states indicate a strong coupling between the two torsional vibrations. A model calculation based on the Hamiltonian previously used by Butcher and Wilson (J. Chem. Phys.40, 1671 (1964)), was carried out to account for the splittings and the vibrational frequencies of the two torsional modes. The barrier to internal rotation of the methyl group is estimated to be V3 = 647 ± 17 cm?1 (1.84 ± 0.05 kcal/mole). 相似文献
6.
The microwave spectra of 3-aminopropanol and three of its deuterium substituted isotopic species have been investigated in the 26.5 to 40 GHz frequency region. The rotational spectrum of only one conformer has been assigned in which presumably a hydrogen bond of the OH---N type exists. The rotational spectra of a number of excited vibrational states have been observed and assignments made for some of these excited states. The average intensity ratio for the rotational transitions between the ground and excited vibrational states indicates that the first excited state is about 120 cm?1 above the ground state.and the next higher state is roughly 200 cm?1 above the ground vibrational state. The dipole moment was determined from the Stark effect measurements to be 3.13 ± 0.04 D with its principal axes components as |μa| = 2.88 ± 0.03 D, |μb| = 1.23 ± 0.04 D and |μc| = 0.06 ± 0.01 D. The possibility of another conformer where the hydrogen bond could be of NH---O type was explored, but the spectra of such a conformer could not be identified. 相似文献
7.
《Journal of Molecular Spectroscopy》1987,123(1):187-196
The microwave and millimetre-wave spectra of CF35Cl3 have been measured in the ground and first excited doubly degenerate (E) vibrational states. Rotational, centrifugal distortion, and quadrupole parameters were obtained for both states. In the E state, strong l-resonance was observed, enabling some rotation-vibration parameters to be accurately determined. In addition, there was a splitting of the (kl − 1) = ± 1 lines due to the asymmetry of the individual quadrupole coupling tensors with respect to the principal inertial axes. 相似文献
8.
The microwave spectra of three isotopic species of chlorine isocyanate, ClNCO, have been measured in the frequency region 8–37 GHz. Spectra have been observed for molecules in both the ground and excited vibrational states, and have yielded values for the rotational constants, inertial defects, centrifugal distortion constants, and nuclear quadrupole coupling constants for both chlorine and nitrogen. The molecule has been shown to be planar, with the following internuclear parameters: fx547-1 < (NCO) = 171° 24′ ± 1° 30′, with Cl and O trans. The principal values of the chlorine nuclear quadrupole coupling tensor were calculated, and were found to be consistent with the derived structure. 相似文献
9.
Arsenic monophosphide has been prepared by laser ablation of arsenic in the presence of PH3. The J = 2-1 and 1-0 transitions in both the ground and first excited vibrational states have been measured with a cavity pulsed jet Fourier-transform microwave spectrometer. An improved equilibrium internuclear distance (re) has been obtained. Hyperfine structure in the rotational spectrum of AsP has been resolved and has led to the first determinations of the As nuclear quadrupole coupling constant and both nuclear spin-rotation constants. The data enable the electronic structure of AsP to be compared with those of other mixed Group 15 diatomic molecules. 相似文献
10.
The microwave spectrum of bullvalene has been investigated in the region 18–40 GHz. In addition to transitions in the ground vibrational state, transitions arising from five excited vibrational states below 600 cm−1 have also been observed. A combination of microwave intensity measurements and infrared and Raman data has been utilized to assign these vibrations. Three of the vibrations are E-type modes at 241, 355, and 588 cm−1. One is an A1-type mode at 445 cm−1, and another is an A2-type at 266 cm−1. The microwave spectrum indicates the presence of a first-order Coriolis interaction for the E modes at 241 and 588 cm−1. The first-order Coriolis coupling constant q = 0.557 MHz for the 241 cm−1 vibration. The spectral results are consistent with C3v symmetry for bullvalene. 相似文献
11.
The microwave spectrum of ethylcyanide-d5 has been recorded from 18.0 to 40.0 GHz. Both a-type and b-type transitions were observed and assigned. Also, the R-branch assignments have been made for three excited states of the internal torsional mode and two excited states of the CN inplane bending mode as well as an excited vibrational state involving both of these motions. The barrier to internal rotation was determined to be 3.00 ± 0.15 kcal/mole from the E, A splittings of the third excited state. The quadrupole coupling constants of the14N nucleus were found to have values of ?3.213, 1.168, and 2.045 MHz for χaa, χbb, and χcc, respectively. These results are compared to those previously obtained on the corresponding hydrogen compound. 相似文献
12.
Shenghai Wu 《Journal of Molecular Spectroscopy》2009,253(1):35-200
Microwave spectra of the hydrogen bonded complex 16OD-16OH2 have been recorded using pulsed-nozzle Fourier transform microwave spectroscopy. The potential splitting, ρ, which describes the partial quenching of the OD orbital angular momentum upon complexation, is determined to be −142.703173(65) cm−1. Within the spectroscopic model employed, this value implies an energy difference of 202.46 cm−1 between the ground (2A′) and first excited (2A′′) states of the complex. The observed value of ρ represents a rather large change of 3.85710(11) cm−1 relative to that in the parent complex and implies a 1.30 cm−1 decrease in the 2A′-2A′′ energy spacing relative to the parent species. Comparison with previous results for the 18OH complex suggests that these changes likely arise from changes in vibrationally averaged geometry upon deuteration. Magnetic hyperfine structure from the deuterium and the water protons is analyzed, as is the nuclear electric quadrupole coupling of the deuterium nucleus. Assuming negligible changes in the axial component of the electric field gradient at the deuterium upon complexation, the deuterium quadrupole coupling constant implies an average angular excursion of the OD bond axis from the vibrationally averaged a-inertial axis of the complex of ∼24°. 相似文献
13.
The results of microwave spectrum investigation of the excited vibrational states of furfural in the frequency range between 49 and 149 GHz are reported. In total 15 excited vibrational states (9 for trans-furfural and 6 for cis-furfural) were assigned and analyzed. Six of the 15 investigated states were assigned for the first time. Accurate values of rigid rotor and quartic centrifugal distortion constants of asymmetric top Hamiltonian have been determined for 13 excited states. Also for some states several sextic and octic level constants were needed in order to fit the data within experimental accuracy. The vt = 3 and vs = 1, va = 1 states of trans-furfural were found to be strongly perturbed and only rotational transitions with low Ka values can be reliably identified in this study. 相似文献
14.
Zbigniew Kisiel Lech Pszczó?kowski Manfred Winnewisser Eric Herbst 《Journal of Molecular Spectroscopy》2005,233(2):231-243
We report the results of a comprehensive reinvestigation of the rotational spectrum of diethyl ether based on broadband millimetre-wave spectra recently recorded at The Ohio State University and in Warsaw, covering the frequency region 108-366 GHz. The data set for the ground vibrational state of trans-trans diethyl ether has been extended to over 2000 lines and improved spectroscopic constants have been determined. Rotational spectra in the first excited vibrational states of the three lowest vibrational modes of trans-trans-diethyl ether, ν20, ν39, and ν12 have been assigned. The v20 = 1 and v39 = 1 states are near 100 cm−1 in vibrational term value and are coupled by a strong c-axis Coriolis interaction, which gives rise to many spectacular manifestations in the rotational spectrum. All of these effects have been successfully fitted for a dataset comprising over 3000 transitions, leading to precise determination of the energy difference between these states, (ΔE/hc)=10.400222(5) cm−1. A newly developed software package for assignment and analysis of broadband spectra is described and made available. 相似文献
15.
Measurements of the microwave spectrum of formamide have been extended in order to account accurately for the effects of centrifugal distortion. A total of 22 new transitions involving J ≤ 29 have been measured for 14NH212CH16O in the ground vibrational state. Combined with previous observations, these transitions have been fit to a model containing five quartic distortion terms and seven sextic terms with a rms deviation of 64 kHz. A large number of resolved quadrupole shifts were fit with an rms deviation of 42 kHz. The remainder of the spectrum for J ≤ 30 has been calculated with standard deviations less then 3 MHz. Correct weighting of the observed transitions has been found to be important. 相似文献
16.
A fit of about 350 rotational levels of the (020), (100), and (001) vibrational states has been performed for H217O as well as for H218O leading to the determination of 51 rotational and coupling constants for each isotopic species. The Fermi-type interaction and the two Coriolis-type interactions have been taken into account by appropriate rotation-vibration operators and the v-diagonal part of the Hamiltonian is, for each vibrational state, a Watson-type Hamiltonian. The results are very satisfactory since 87% of the experimental levels are reproduced within 15 × 10?3 cm?1. 相似文献
17.
A method is given for the analysis of the rotational spectrum in the ground and excited states of C3v molecules; it consists in a direct diagonalization of the energy matrix including all elements whose contribution can become significant for the analysis up to the sixth order of approximation.The method of factoring the energy matrix into four submatrices A1, A2, E, E, according to the symmetry species of the full point group C3v, is given. The programm enables the calculation of the rotational frequencies and also carries out by a least-squares method the fitting of the molecular constants for vibrational states v = 0 (ground state) and vE = 1, 2, 3, and 4, separately or simultaneously over several of these states.The analysis of the rotational spectrum of CH3C15N in the v8 = 0, 1, 2 states is given as an example. 相似文献
18.
The gas phase electron resonance spectra of NCO in its ground 2Π3/2 vibronic state and in two excited vibronic states are described. Theoretical analysis of the spectra yields effective g values for the three states. In additon the 14N magnetic hyperfine and electric quadrupole coupling constants and the electric dipole moment are determined. The theory of the Renner coupling of electronic and vibrational motion is extended, and shown to account for anomalous contributions to the g values. The theory also shows that these contributions are closely related to the Renner coupling constant. 相似文献
19.
L. Bizzocchi 《Journal of Molecular Spectroscopy》2006,235(1):117-124
The rotational spectra of 28SiF2, 29SiF2, and 30SiF2 in their ground vibrational states, as well as those of 28SiF2 in the v1 = 1, v2 = 1, v3 = 1, and v2 = 2 excited states have been studied in selected frequency regions between 80 and 700 GHz. Transitions involving a large range of quantum numbers have been observed, so that precise rotational and quartic centrifugal distortion constants could be determined for each of the spectra investigated. In addition, the complete set of sextic distortion constants was also obtained for the most abundant isotopomer in its ground vibrational state. The quadratic and cubic force constants of silicon difluoride have been refined by a least-squares procedure using a larger and more precise set of data. 相似文献
20.
《Molecular physics》2012,110(21-22):2621-2632
The vibration–rotation spectra of 13C substituted acetylene, 13C2H2, have been recorded in the region between 60 and 2600?cm?1 at an effective resolution ranging from 0.001 to 0.006?cm?1. Three different instruments were used to collect the experimental data in the extended spectral interval investigated. In total 9529 rotation vibration transitions have been assigned to 101 bands involving the bending states up to v tot?=?v 4?+?v 5?=?4, allowing the characterization of the ground state and of 33 vibrationally excited states. All the bands involving states up to v tot?=?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 v tot?=?4. These could be satisfactorily reproduced only by adopting a set of effective constants for each vibrational manifold, in addition to the previously determined parameters, which were constrained in the analysis. 相似文献