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1.
The 71 and 91 vibrational states of deuterated species of formic acid molecule DCOOH have been recorded by a FTIR spectrometer in the region 450- at a resolution of and a millimeter wave spectrometer. In the analysis microwave transitions from literature were used in addition to 14 835 assigned IR and 114 millimeter wave lines in the 71 and 91 vibrational states. The analysis resulted in band origins, rotational, centrifugal distortion, and eight interaction parameters of the Coriolis coupled 71 and 91 vibrational states. RMS deviation of the fit was for the IR data and the maximum values of J and Ka quantum numbers in the fit were 64, 28 and 64, 30 for 71 and 91 states, respectively.  相似文献   

2.
The gas phase infrared spectrum of monoisotopic H3Si37Cl has been reinvestigated in the ν1/ν4 region near 2200 cm−1, using a Fourier transform spectrometer, with a nominal resolution of 0.0027 cm−1. The rovibrational analysis confirms, besides the weak Coriolis x, y resonance between the (v1 = 1) and (v4 = 1) levels, the existence of two strong local perturbations in the ν4 band. These are caused by rotational (Δk = Δl = ±1) type resonances with and , respectively. Another local perturbation of the 12 ? KΔK ? 14 subbands of the ν4 band, probably due to a (Δk = Δl = ±1) interaction with , was detected and analyzed. All these local perturbations have been studied individually using a simple model of two interacting sublevels. Without the transitions involved in the local perturbations, more than 2000 lines of the ν1/ν4 band system were used to obtain a complete set of vibration-rotation parameters set for the v1 = 1 and v4 = 1 states. By means of a band contour simulation, both the transition moment ratio ∣M4:M1∣ = 1.25 and a positive sign of the Coriolis intensity perturbation were determined.The present results, together with the accurate existing data for ν2, ν3, ν5, and ν6 bands, allowed us to derive the experimental values, Ae = 2.8722945(37) cm−1 and Be = 0.2182248(22) cm−1, which are compared with those of ab initio calculations.  相似文献   

3.
Previous studies of the parallel bands 2ν2 and 50 of CH3Br by the two first authors have been completed by the analysis of the weaker perpendicular band ν2 + ν5, centered near 2745 cm?1. It is well known that the v2 = 1 and v5 = 1 states of methylbromide are linked by an x-y-type Coriolis interaction. Therefore, in the 2500–2900-cm?1 range, the levels
(v2=2), (v52, l5=0), (v5=2, l5±2), (v5=v2=1, l=5±1)
are linked by a similar interaction. Least-squares and prediction programs have been written to treat this kind of problems and they have been satisfactorily applied to both isotopic species, CH379Br and CH381Br. A localized resonance in the K = 0 subband of ν2 + ν5 has been shown to be due to the 3ν3 + ν6 band. No evidence for a strong Fermi resonance between ν1 and 50 has been found.  相似文献   

4.
The high resolution infrared spectrum of mono-isotopic F37Cl16O3 has been studied in the regions of ν1, ν2, ν4 and ν2 + ν5 bands, centered at 1060.20, 707.16, 1301.71 and 1292.15 cm−1, respectively. The ν1 and ν2 parallel bands are unperturbed so their analysis was straightforward and 3355 and 2433 transitions were assigned, respectively. The band origins, the rotational and centrifugal molecular constants in the v1 = 1 and v2 = 1 states have been determined, with standard deviation of the fits σ = 0.00019 and 0.00018 cm−1. The ν4 fundamental is affected by an anharmonic resonance with the ν2 + ν5 combination band. The kl > 0 sublevels cross at kl ? 27 because of the opposite values of and . The anharmonic resonance constant  cm−1 has been derived. The Δl = Δk = ±2 and Δl = 0, Δk = ±3 essential resonances have been found to be effective in ν4, while in ν2 + ν5 only the Δl = Δk = ±2 one was active. A total of 5721 transitions have been assigned, 25% of them belonging to ν2 + ν5. The rovibrational parameters and the interaction constants of F37Cl16O3 have been obtained. The standard deviation of the fit is 0.0006 cm−1, six times the estimated data precision. The equilibrium geometry of perchloryl fluoride has been determined from the Ae and Be constants of F35Cl16O3 and F37Cl16O3. Using the A0 and B0 constants of all the symmetric species the r0 geometry has also been derived.  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 Fourier transform gas-phase IR spectrum of 1,2,3-thiadiazole, C2H2N2S, has been recorded with a resolution of ca. 0.003 cm−1 in the 700-1100 cm−1 spectral region. Four fundamental bands ν6(A/; 1101.8 cm−1), ν7(A/; 1038.8 cm−1), ν9(A/, 858.9 cm−1), and ν13(A//; 746.2 cm−1) have been analyzed using the Watson model in A-reduction. Two additional bands, ν8 (A/; 894.6 cm−1) and ν12(A//; 881.2 cm−1) were assigned by their weak Q-branches. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. A number of weak global and local interactions are present in the bands. The resonances identified were qualitatively explained by Coriolis type perturbations with neighboring levels. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational α-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement.  相似文献   

7.
The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C2H2N2S, has been recorded with a resolution of ca. 0.003 cm−1 in the 800-1500 cm−1 spectral region. Five fundamental bands ν2(A1; 1391.9 cm−1), ν4(A1; 964.4 cm−1), ν5(A1; 894.6 cm−1), ν9(B1; 821.5 cm−1), and ν14(B2; 898.4 cm−1) have been analysed using the Watson model. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. The ν4 and ν9 bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying ν5 and ν14 bands. This dyad system has been analysed by a model including first and second order c-Coriolis resonance using the theoretically predicted Coriolis coupling constant . The ν2 band is strongly perturbed by a local resonance, and we obtain a set of spectroscopic parameters using a model including second order a-Coriolis resonance with the inactive ν10 + ν14 band. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational α-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement.  相似文献   

8.
9.
Rotationally resolved vibrational spectra of the three lowest frequency bands of the four-membered heterocycle azetidine (c-C3H6NH) have been collected with a resolution of 0.00096 cm−1 using the far infrared beamline at the Canadian Light Source synchrotron. The modes observed correspond principally to motions best described as: β-CH2 rock (ν14) at 736.701310(7) cm−1, ring deformation (ν15) at 648.116041(8) cm−1, and the ring puckering mode (ν16) at 207.727053(9) cm−1. A global fit of 14 276 rovibrational transitions from the three bands provided an accurate set of ground state spectroscopic constants as well as excited state parameters for each of the three vibrational modes. The ground state structure was determined to be that of the puckered conformer having the NH bond in an equatorial arrangement.  相似文献   

10.
The infrared spectrum of propynal, C2HCHO, is studied at high resolution (0.003 cm−1) in the range 570-640 cm−1. The relatively intense ν11 (CC-H out-of-plane bend, 693 cm−1) and ν7 (CC-H in-plane bend, 651 cm−1) fundamental bands are linked by a strong a-type Coriolis interaction. The somewhat weaker ν8 (CCO in-plane bend, 614 cm−1) fundamental has a significant Fermi-type interaction with the “dark” background state 3ν9 (∼618 cm−1). About 1400 lines are assigned and analyzed in terms of a four-state fit in order to obtain accurate band origins, rotational and centrifugal distortion parameters, and Fermi and Coriolis interaction parameters. This represents the first systematic high-resolution infrared study of propynal.  相似文献   

11.
The high resolution infrared spectra of monoisotopic F35Cl18O3 and F37Cl18O3 have been studied in the region of the ν4 fundamentals, centered at 1278.3 and 1263.3 cm−1, respectively. Large perturbations are observed in both bands due to a Fermi type anharmonic resonance with the ν2 + ν5 combination bands, centered at 1270.7 cm−1 in F35Cl18O3 and 1257.3 cm−1 in F37Cl18O3. In particular, they affect the kl > 0 levels of the v4 = 1 and v2 = v5 = 1 states which cross at kl ? 18 in F35Cl18O3 and kl ? 3 in F37Cl18O3, due to the opposite values of and . The Δl = Δk = ±2 and Δl = 0, Δk = ±3 essential resonances are also effective in the excited states of the dyad in F35Cl18O3, while in F37Cl18O3 only the Δl = Δk = ±2 one is active. In the spectrum of F35Cl18O3 3423 transitions have been assigned, 10% of them belonging to ν2 + ν5. The rovibrational parameters and the interaction constants between the v4 = 1 and v2 = v5 = 1 levels have been obtained. The depertubed band origins of ν4 and ν2 + ν5 are 1277.310567(165) and 1271.753733(195) cm−1, respectively, and the anharmonic resonance constant is 2.804416(153) cm−1. For F37Cl18O3, 3022 transitions have been assigned, 38% belonging to the ν2 + ν5 combination band. The depertubed band origins are 1260.856338(123) and 1259.872338(134) cm−1, for ν4and ν2 + ν5 and the constant is 2.9350669(405) cm−1. The equilibrium geometry of perchloryl fluoride, re (ClO) = 139.7(3) pm, re (ClF) = 161.0(5) pm, and αe (OClO) = 115.7(4) degree, has been determined using the Ae and Be equilibrium constants of the four symmetric isotopologues of perchloryl fluoride, F35/37Cl16O3 and F35/37Cl18O3.  相似文献   

12.
High resolution infrared spectra of 121SbHD2 and 123SbHD2 have been studied in the region of ν1, the Sb-H stretching fundamental, from 1780 to 1990 cm−1. The 2ν1 stretching overtone band of 123SbHD2, located in the 3640-3790 cm−1 range, has also been investigated. The SbHD2 molecule is an asymmetric rotor of Cs symmetry with the asymmetry parameter κ = 0.61. The ν1 band is of hybrid type, formed by strong C-type and weak B-type transitions, and almost unperturbed. For 123SbHD2, 2092 transitions have been assigned: 70% of these belong to the C component, the other 30% are of B-type. The assigned transitions have been fitted using a Watson type S-reduced Hamiltonian in the IIIl representation, with a standard deviation of the fit σ = 0.45 × 10−3 cm−1. In order to determine the ground state parameters all possible ground state combination differences (GSCD) have been generated from the ν1 transitions. In total, 3942 GSCD up to J = 27,  = 25, and  = 20 have been fitted with σ = 0.52 × 10−3 cm−1. Only C-type transitions have been observed in the weak 2ν1 overtone band. The 556 assigned transitions have been fitted with σ = 2.6 × 10−3 cm−1 using the same Hamiltonian as for ν1. In the ν1 band of 121SbHD2 771 C-type transitions have been assigned, and the v1=1 spectroscopic constants obtained from a fit with σ = 0.70 × 10−3 cm−1. Using 618 GSCD the ground state spectroscopic constants of 121SbHD2 have been derived with σ = 1.0 × 10−3 cm−1. The molecular parameters for the ground and the v1=1 states of the two isotopologues agree well. The quartic theoretical ab initio force field of SbH3 has been used to predict all relevant spectroscopic parameters for 123SbHD2, 121SbHD2, 123SbH2D, and 121SbH2D. Relations between the harmonic frequencies and between the anharmonicity constants obtained in the expanded local mode theory, for the XH3 → XH2D/XHD2 isotopic substitution, have been compared with those obtained in the present study.  相似文献   

13.
Pressure-induced line shift coefficients have been measured for more than 200 rovibrational lines of NH3 perturbed by O2 at room temperature (T = 295 K) in some branches of the ν2, 2ν2, and ν4 bands. These lines with J values ranging from 1 to 13 are located in the spectral range 800-1800 cm−1. Experiments were made with a high-resolution Fourier transform spectrometer. The treatment of vibration-rotation lines includes interference effects caused by the overlapping of lines. The O2 pressure-induced shift coefficients have been derived from the non-linear least-squares multi-pressure fitting technique. The results illustrate a vibrational dependence of line shifts with vibrational quantum number. Most of the measured shifts are negative in the ν4 band. They are positive for the ν2 and 2ν2 bands. The measured shift coefficients are compared with previous measurements and with those calculated from a semiclassical theory based upon the Robert-Bonamy formalism extended to the case of symmetric top molecule with inversion motion. The predictions are generally in satisfactory agreement with the experimental data. Analyses of measured and predicted results illustrate that these shifts mainly originate from the isotropic part of the intermolecular potential.  相似文献   

14.
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   

15.
The results of millimeter and submillimeter wave rotational spectroscopy are used to simulate the complex structure of the 2ν9-ν9 and ν5-ν9 hot bands. The comparison data were obtained with a high-resolution Bruker FTIR. The combination of the quality of these data and the complexity of the spectra of these interacting states represents a stringent test for the simulation. It is shown that the agreement is very good and that this approach is generally advantageous. From this simulation, the ratios of the transition dipole moments for the 2ν9-ν9 and ν5-ν9 hot bands with respect to the ν9 fundamental band were found to be 1.38(11) and 0.67(20), respectively. Using these results, the calculated integrated band intensities for the hot bands at were determined to be and . These results were used to successfully simulate high-resolution stratospheric spectra obtained from a balloon flight of the FIRS-2 spectrometer. The more general problem of the rotation-vibration database and the optimal use of both microwave and infrared data to define it is discussed. It is concluded that it is best if the combination of data takes place at the level of the original spectra.  相似文献   

16.
For the first time the infrared spectrum of the AsHD2 molecule has been measured in the region of the bending fundamental bands ν3, ν4, and ν6 on a Fourier transform spectrometer with a resolution of 0.0024 cm−1 and analyzed. More than 5500 transitions with Jmax = 26 have been assigned and used both to obtain “ground state combination differences” and for the determination of upper state ro-vibrational energies of the triad (001000), (000100), and (000001). Rotational parameters including centrifugal distortion coefficients up to octic terms of the ground vibrational state were calculated by fitting more than 500 “ground state combination differences” with Jmax and . The obtained set of 24 parameters provides a rms-deviation of 0.00011 cm−1. The upper energies were fitted with 52 parameters of an effective Hamiltonian which takes into account strong resonance interactions between all vibrational states of the triad (001000), (000100), and (000001). The rms-deviation for the energy levels considered in the fit is 0.00014 cm−1.  相似文献   

17.
The high-resolution (0.0030 cm−1) Fourier transform infrared spectrum of CH279BrF has been studied in part of the atmospheric window between 910 and 980 cm−1, the region of the ν9 (935.847 cm−1) and ν5 + ν6 (961.239 cm−1) bands. The ν9 fundamental consists of a pseudo a-type band induced by Coriolis coupling with ν5 + ν6, in turn exhibiting a predominant a-type structure. Several interactions connecting these levels and the dark state 3ν6 have been assessed. The whole data set is treated using Watson’s A-reduced Hamiltonian in the Ir representation implemented with first order a- and b- and c-type Coriolis terms. A detailed analysis of the rotational structure yields a set of accurate upper-state parameters up to quartic distortion terms for ν9 and ν5 + ν6. In addition, spectroscopic information about the dark ternary overtone of ν6 has been obtained.  相似文献   

18.
The P-H stretching bands ν1/ν5 and 2ν1/ν1+ν5 were recorded using a Bruker 120 HR interferometer with a resolution of 0.0042 and 0.0088 cm−1, respectively, and analyzed. From the fits 33 and 50, respectively, vibrational, rotational, centrifugal distortion, and resonance interaction parameters were obtained. These reproduce 668 and 497 rovibrational energies of the pairs of states ν1/ν5 and 2ν1/ν1+ν5 with experimental accuracies, rms=0.00016 and , respectively. “Local mode” behavior of the PH2 fragment is established and discussed in detail.  相似文献   

19.
The ν2 (CD3 symmetrical deformation) and ν5 (CD3 degenerate deformation) fundamental bands of CD3Br were studied by 9.4- and 10.4-μm CO2 laser Stark spectroscopy. Stark resonances originating from 28 and 53 rovibrational transitions of the ν2 and ν5 bands, respectively, were assigned for each of the isotopic species, CD379Br and CD381Br. These two bands were simultaneously analyzed with explicit inclusion of the ν2-ν5 Coriolis interaction, yielding precise molecular constants in the ν2 and ν5 excited states as well as the Coriolis coupling constant. The molecular constants obtained are consistent between the two isotopic species and are in good agreement with the results of high-resolution infrared studies. The band origins and dipole moments are
  相似文献   

20.
H2-broadening coefficients are measured for 41 transitions of PH3 in the QR branch of the ν2 band and the PP, RP, and PQ branches of the ν4 band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 2 to 16 and K from 0 to 11 are located between 995 and . The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter model provides larger broadening coefficients than the Voigt model. These coefficients γ0(J,K) are found to decrease slightly on the whole as J increases and they decrease significantly for K values approaching or equal to J(J?4). The H2-broadenings are also calculated on the basis of a semiclassical model of interacting linear molecules, using an atom-atom Lennard-Jones potential in addition to the weak electrostatic contributions. The theoretical results are in satisfactory agreement with the experimental data and reproduce the J and K dependencies of the broadenings, but the decrease observed for the QR(J,K) transitions with K=J is notably overestimated.  相似文献   

CD379BrCD381Br
ν2991.396 82 (18)991.388 46 (17)cm?1
ν51055.469 00 (12)1055.466 32 (12)cm?1
μ01.830 42 (52)1.829 84 (47)D
μ21.829 93 (48)1.829 57 (46)D
μ51.832 23 (60)1.831 19 (56)D
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