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1.
The infrared spectrum of isotopically pure CH279BrCl has been recorded at a resolution of 0.0023 cm−1 (FWHM) in the range 550-800 cm−1 with a Bruker IFS 120 HR Fourier transform spectrometer in Wuppertal. Here we report the full rotational analysis of the ν4 and ν5 fundamentals and of the hot-bands ν4+ν6ν6 and ν5+ν6ν6. Ground state combination differences were constructed for all bands, yielding improved ground state constants, up to quartic terms, as well as reliable rotational constants for the ν4, ν5, and ν6 states.  相似文献   

2.
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regions of this study are in good agreement with the line positions and the relative intensities specified in an unpublished complete line listing for the v2 band prepared by Linda Brown (see full text for reference).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   

3.
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   

4.
The two lowest vibrational states of 35Cl35ClO2, v4=1 (A′) and v6=1 (A″), were investigated between 223 and 500 GHz. More than 250 rotational transitions were recorded with J and Ka up to 71 and 34, respectively. The spectra are heavily perturbed by strong c-type and weaker a-type Coriolis interactions. Near degeneracies of rotational levels of the two vibrational states having ΔJ=0, ΔKa=5 to 1, and ΔKaKc= odd cause moderate to severe perturbations in the rotational structure, preventing the states from being fit as isolated ones. Distortions in the hyperfine structure facilitated the assignment of rotational quantum numbers. Several resonantly interacting levels with ΔKa=5 to 2 were accessed, and a number of transitions between the states were observed. While resonant Coriolis interaction with ΔKa=1 occurs only at Ka>40, the effects of this interaction are so severe that nonresonant interaction considerably perturbs the highest KaQ-branches observed. The observed transitions could be fit to within experimental uncertainties employing the first-order Coriolis coupling constants fixed to those from the harmonic force field, sextic distortion constants fixed to those of the ground state, and some higher order Coriolis terms. The energy difference calculated from the fit agrees well with that obtained from the matrix-isolation infrared spectrum. Quadrupole coupling constants were determined for both Cl nuclei and both vibrational states.  相似文献   

5.
The FTIR spectrum of pentafluoroethane (R125) was measured in the mid infrared region from 900 to 4000 cm−1. Vibrational assignments for R125 are revised by comparison of previous and current experimental data with ab initio calculations at both the MP2/6-311+(d,p) and B3LYP/TZV+(3df,3p) levels of theory. High resolution FTIR spectra were recorded at room temperature and in an enclosive flow cell at a rotational temperature of 140 K. The cold spectrum was sufficiently resolved to enable rovibrational analyses of the overlapping ν4 (1200.7341 cm−1) and ν13 (1223.3 cm−1) bands, which have a/c hybrid and b-type character, respectively. Ground state combination differences were used to confirm assignment of 2375 lines to ν4 (Jmax = 86, Ka max = 50) and 2921 lines to ν13 (Jmax = 60, Ka max = 54). Effective rotational and centrifugal distortion constants were determined for ν4, and the polarization ratio was found to be . Severe Coriolis perturbations prevent any satisfactory fit to the ν13 band.  相似文献   

6.
The ν11 band of ethylene-d4 was observed in a region from 2174 cm?1 to 2227 cm?1 with Doppler-limited resolution (about 3 × 10?3 cm?1) by using a diode laser spectrometer. The qP, qQ, and qR branches with five weak sQ lines were analyzed up to Ka = 12 to determine the ground-state as well as the upper-state molecular constants. A Coriolis interaction, possibly a b-type one with the ν2 + ν7 band, was found to perturb high-Ka lines. The discrepancy between the observed and the calculated inertia defects in ν11 was explained by the interaction.  相似文献   

7.
The ν2 (CO stretch) fundamental band of formyl fluoride (HFCO) was studied in the region 1800 to 1910 cm?1 using the two techniques of intracavity CO laser Stark spectroscopy at sub-Doppler resolution and Fourier transform spectroscopy at Doppler-limited resolution. Accurate values of the molecular parameters of the ground and excited (v2 = 1) vibrational states were obtained from a combined fit of the ν2 band data and available microwave data. The results include precise determinations of the electric dipole moment components (μa and μb) of HFCO in the ground and excited states.  相似文献   

8.
High-resolution Fourier transform spectrum of phosphine (PH3) at room temperature has been recorded in the region of the 3ν2 band (2730-3100 cm−1) at an apodized resolution of 0.005 cm−1. About 200 vibration-rotation transitions have been least squares fitted with an rms of 0.00039 cm−1 after taking into account the ΔK = ±3 interaction.  相似文献   

9.
The ν1 (CO stretching) and ν2 (CF stretching) bands of the FCO radical were observed with Doppler-limited resolution by an infrared diode laser spectrometer with Zeeman and source modulation. The FCO radical was generated by a 60-Hz discharge in one of the following three gas mixtures: O2 + C2F4, CO + SF6, and CO + C2F4, all diluted with He. The observed spectra were analyzed to determine the rotational constants, the centrifugal distortion constants, and the spin-rotation interaction constants. The band origins, 1861.6372(1) and 1026.1283(1) cm?1 [with standard errors in parentheses], which were obtained, were found to agree well with matrix data, 1857 and 1023 cm?1, respectively. The assignment of the observed spectra to the FCO radical was further supported by observing the ν1 band of F13CO, which was obtained from 13CO and SF6. The molecular structure and the force field of FCO are briefly discussed by using molecular constants obtained from the observed spectra.  相似文献   

10.
The weak 2ν3 overtone band of the three isotopomers of cyanogen iodide, I12C14N, I13C14N, and I12C15N, has been recorded in the range from 4200 to 4400 cm−1 with a resolution of 0.02 cm−1 using a Fourier transform infrared spectrometer. The following band origins have been determined from the analysis of the spectra: ν0 (I12C14N)=4332.8368 cm−1, ν0 (I13C14N)=4235.7355 cm−1, and ν0 (I12C15N)=4274.2851 cm−1. This allowed us to achieve complete knowledge of the energies for all levels of ICN corresponding to double vibrational excitation. An improved evaluation of the quartic force field of cyanogen iodide has been performed using the new data obtained together with those already known from previous works.  相似文献   

11.
A high-resolution (0.002 cm−1) infrared absorption spectrum of methylene fluoride-d2 (CD2F2) of the lowest fundamental mode ν4 in the region from 460 to 610 cm−1 has been measured on a Bruker IFS 120-HR Fourier transform infrared spectrometer. More than 3500 transitions have been assigned in this B-type band centered at 521.9 cm−1. The data have been combined with upper state pure rotational measurements in a weighted least-squares fit to obtain molecular constants for the upper state resulting in an overall standard deviation of 0.00018 cm−1. Accurate value for the band origin (521.9578036 cm−1) has been obtained and inclusion of transitions with very high J (?60) and Ka (?34) values has resulted in improved precision for sextic centrifugal distortion constants, in particular DK, HKJ, and HK.  相似文献   

12.
High resolution (0.001 cm−1) coherent anti-Stokes Raman spectroscopy (CARS) was used to directly examine the ν1 symmetric stretching mode of the planar symmetric D3h molecules 10BF3 and 11BF3. Simulations of the spectra were done using ν1 rovibrational parameters deduced from published infrared hot-band and difference-band studies and the close similarity to the observed CARS spectra confirms the validity of the infrared constants. No significant perturbations by Fermi resonance or Coriolis interactions with nearby states are observed, in marked contrast to the case of sulfur trioxide, a similar D3h molecule recently studied. In the harmonic approximation, the 10BF3 and 11BF3ν1 Q-branches would be identical since the isotopic substitution is at the center of mass but, interestingly, the ν1 stretching frequency for 11BF3 is found to be 0.198 cm−1higher than for the lighter 10BF3 isotopomer. This counterintuitive result is reproduced almost exactly (0.200 cm−1) by ab initio calculations (B3LYP/cc-pVTZ) that included evaluation of cubic and quartic force constants and xij anharmonicity constants. The ab initio computations also predict to within 1% the ΔB, ΔC changes in the rotational constants in going from the ground state to the v1 = 1 vibrational level. The results illustrate nicely the complementary interplay of modern infrared, Raman, and ab initio methods in obtaining and analyzing rovibrational spectra.  相似文献   

13.
The rotational spectra of the deuterium cyanide isotopic species DCN, D13CN, DC15N, and D13C15N were recorded in the vibrational ground and first excited bending state (v2=1) up to 2 THz. The R-branch transitions from J=3←2 to J=13←12 were measured with sub-Doppler resolution. These very high resolution (∼70 kHz) and precise (±3-10 kHz) saturation dip measurements allowed for resolving the underlying hyperfine structure due to the 14N nucleus in DCN and D13CN for transitions as high as J=10←9. Additional high JR-branch (J=25←24 to J=28←27) transitions around 2 THz and direct l-type (ΔJ=0, J=19 to J=25) transitions from 66 to 118 GHz were recorded in Doppler-limited resolution. For the ground state of D13C15N, the J=1←0 transition was measured for the first time. The transition frequency accuracies for the other deuterated species were significantly improved. These new experimental data, together with the available infrared rovibrational data and previously measured direct l-type transitions, were subjected to a global least squares analysis for each isotopomer. This yielded precise sets of molecular constants for the ground and first excited vibrational states, including the nuclear quadrupole and magnetic spin-rotation coupling constants of the 14N nucleus for DCN and D13CN. The hyperfine structure due to the D, 13C, and 15N nuclei have not been resolved, but led to a broadening of the observed saturation dips.  相似文献   

14.
The vibration-rotation spectrum of the HO2ν2 bending fundamental band was observed by a semiconductor diode laser spectrometer with a Zeeman modulation technique. The wavelength of the laser was measured by a high-precision λ meter. Of 153 lines which were observed by Zeeman modulation, 137 lines were assigned. A least-squares analysis was carried out on 131 observed lines with 1 ≦ N ≦ 13 and 0 ≦ Ka ≦ 4, to determine the rotational constants, the centrifugal distortion constants, and the spin-rotation interaction constants in the ν2 state. The band origin, which was also derived, is 1391.7540 (2) cm?1 [the value in the parenthesis denotes the standard error]. The force field of the HO2 molecule is briefly discussed using molecular constants obtained in previous works and in the present work.  相似文献   

15.
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   

16.
The vibration-rotation spectrum of the ν9 band of C2H5Cl was recorded using a Nicolet 7199 Fourier Transform Infrared Spectrometer; the Q-branch, R(5)-R(6) multiplets, and P(21)-P(22) multiplets were investigated using a tunable semiconductor diode laser spectrometer. Constants derived from these assignments are (cm?1) ν9 = 973.8379(2), A9 = 1.039516(3), B9 = 0.183081(7), C9 = 0.164505(8). The line which coincides with the CO2 laser 10R(6), which has been employed in multiphoton dissociation studies, is tentatively assigned to the 203 18-213 19 transition. In addition, a very strong coincidence of transitions 199 11-199 10 and 199 10-199 11 with the CO2 10R(16) line is found, which can provide a good candidate for laser chemistry and infrared double resonance spectroscopy.  相似文献   

17.
The five Q branches, PQ1, RQ0, RQ1, RQ2, and RQ3, of the ν6 band of methyl fluoride 12CH3F were observed by using a tunable diode laser spectrometer and were analyzed to obtain the following molecular constants (in cm?1): ν?6 = 1182.67605(80), A6 = 5.2006(14), ()6 = 1.5437(11), and ()6ηK = 1.6(11) × 10?4, with 2.5 times the standard errors in parentheses. The precision of the band origin may, however, be 0.001–0.002 cm?1 because of the wavelength uncertainties of the N2O spectral lines used as the references. An analysis of the RQ0 subband determined the sign of the q6 constant to be positive. The α6A, α6B, and q6 constants of methyl fluoride are discussed in terms of the anharmonic potential field.  相似文献   

18.
The infrared absorption spectrum of the ν12 fundamental band of ethylene-d (C2H3D) has been recorded with an unapodized resolution of 0.004 cm−1 in the wavenumber range of 1340-1460 cm−1 using the Fourier transform technique. By assigning and fitting a total of 870 infrared transitions using a Watson’s A-reduced Hamiltonian in the Ir representation, three rotational and five quartic centrifugal distortion constants for the upper state (v12 = 1) were determined for the first time. The rms deviation of the fit was 0.00044 cm−1 which is close to the experimental precision of the absorption lines. The A-type ν12 band centred at 1400.762811 ± 0.000041 cm−1was found to be relatively free from local frequency perturbations. The inertial defect Δ12 was found to be 0.20928 ±  0.00002 μÅ2.  相似文献   

19.
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   

20.
We report a rovibrational analysis of the ν4 and ν6 fundamentals and the 2ν5 overtone of HNSO from high-resolution Fourier transform infrared spectra. The ν6 band (out-of-plane bend) centred at 757.5 cm−1 is c-type. The ν4 band (HNS bend) centred at 905.9 cm−1 is predominantly a-type with a very weak b-type component (). Numerous global perturbations and localized avoided crossings affecting the v4 = 1 rotational levels were successfully treated by inclusion of Fermi and c-axis Coriolis resonance terms between v4 = 1 and v5 = 2, and a b-axis Coriolis resonance term between v4 = 1 and v6 = 1. The latter term gives rise to an avoided crossing with an extraordinary ΔKa = 5 selection rule. The Fermi resonance between v4 = 1 and v5 = 2 gives rise to strong mixing of their rotational wavefunctions in the vicinity of Ka = 18. The resultant borrowing of intensity made it possible for 2ν5 transitions in the range Ka = 16–19 to be assigned and included in a global rovibrational treatment of all three band systems.  相似文献   

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