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1.
Previous measurements of rotational spectrum of aziridine up to 1.85 THz have been supplemented by new data in 225-660 GHz frequency range. A total of 1465 transitions (915 of them are newly assigned ones) with maximum values of J = 59 and Kc = 50 were fit to a standard Watson Hamiltonian using the S- and A-reductions and the representations Ir and IIIr. Although aziridine is an asymmetric oblate top, the combination (A, IIIr) gives the worst results. From the point of view of the convergence of the Hamiltonian, the best results are obtained with the combination (S, IIIr). It is explained that the failure of the combination (A, IIIr) is due to the large value of the parameter σ=(2C-A-B)/(A-B) which makes some sextic centrifugal distortion constants much too large impeding the convergence of the Hamiltonian. It is also shown that the calculation of the centrifugal distortion constants from a force field is sometimes an ill-conditioned operation. Finally, the use of a non-reduced Hamiltonian (with six quartic centrifugal distortion constants) was successful in the particular case thanks to the method of predicate observations.  相似文献   

2.
We have calculated the three-dimensional potential energy surfaces for the 1 2A′ and 1 2A″ states of BrCN+ at the MR-SDCI_DK+Q/[QZP-ANO-RCC (Br, C, N)] level of theory, where MR-SDCI_DK means ‘multi-reference single and double excitation configuration interaction calculation with Douglas-Kroll Hamiltonian.’ These ab initio potential energy surfaces have a common minimum (corresponding to the state) at a linear equilibrium structure with re(Br-C) = 1.735 Å and re(C-N) = 1.199 Å. Variational RENNER calculations yield a zero-point averaged structure (with the structural parameters calculated as expectation values over rovibrational wavefunctions) with 〈r(Br-C)〉0 = 1.739 Å, 〈r(C-N)〉0 = 1.204 Å, and 〈∠(Br-C-N)〉0 = 172(4)°. A severe Fermi resonance between 2ν2 and ν3 has been found theoretically for the 2A″ potential energy surface. Comparing the ab initio zero-point averaged structure with a recent, experimentally derived r0 structure, it is concluded that the effects of large-amplitude bending motion should be taken into account explicitly in the process of deriving the r0 structure from the experimental values of the rotational constants. The electronic structure of BrCN+ has also been discussed.  相似文献   

3.
The second overtone band 3ν1 of sulfur dioxide has been studied for the first time with high resolution rotation-vibration spectroscopy. About 3000 transitions involving about 900 upper state energy levels with have been assigned to the 3ν1 band. In the analysis, an effective Hamiltonian taking into account accidental interactions between the vibrational states (3 0 0), (2 2 0), and (0 4 1) was used. The Watson operator in A-reduction and Ir representation was used in the diagonal blocks of the Hamiltonian. As the result of analysis a set of parameters reproducing the initial experimental data with the rms = 0.00028 cm−1 was obtained.  相似文献   

4.
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   

5.
Monodeuterated diacetylene (HCCCCD) and its 13C-substituted species H13CCCCD, HC13CCCD, HCC13CCD, and HCCC13CD were investigated by Fourier transform microwave spectroscopy. The D nuclear quadrupole splittings were almost completely resolved. For H13CCCCD hyperfine splittings caused by the anisotropic nuclear spin-spin interaction between the H and 13C nuclei were also observed. The analysis yielded rotational constants, centrifugal distortion constants, and the constants for the nuclear quadrupole coupling and anisotropic nuclear spin-spin interaction. The substitution structure of HCCCCD was calculated as follows: rs(C-H) = 1.056054(39) Å, rs(CC) = 1.208631(4) Å, rs(C-C) = 1.374117(6) Å, rs(CC) = 1.208116(4) Å, and rs(C-D) = 1.056231(17) Å, in the order of the arrangement of the bonds. A rough estimate of the equilibrium structure is also presented. The eQq constant for the deuterium nucleus is 0.2061(4) MHz. The anisotropic 13C-H spin-spin interaction constant was experimentally determined for the first time as b = −29.2(15) kHz, which is defined as the coefficient of (3I2zI3z − I2 · I3), where I2 and I3 denote the H and 13C nuclear spins, respectively, and I2z and I3z their components along the molecular axis. The observed b constant is not accounted for by the direct magnetic dipole-dipole interaction only, suggesting a significant contribution from indirect anisotropic interaction.  相似文献   

6.
The Fourier transform infrared (FTIR) spectrum of the ν3 band of C2H3D was measured at an unapodized resolution of 0.0063 cm−1 in the 1240-1340 cm−1 region. Rovibrational constants for the upper state (ν3 = 1) up to five quartic and two sextic centrifugal distortion terms had been obtained by assigning and fitting a total of 1037 infrared transitions using a Watson’s A-reduced Hamiltonian in the Ir representation. The root-mean-square deviation of the fit was 0.00051 cm−1. The ground state rovibrational constants were also determined by a fit of 674 combination differences together with 21 microwave frequencies from the present infrared measurements with a root-mean-square deviation of 0.00040 cm−1. The upper state (ν3 = 1) and ground state rovibrational constants of C2H3D represent the most accurate values obtained so far. The A-type ν3 band, centred at 1288.788826 ± 0.000044 cm−1 was found to be relatively free from local frequency perturbations. From the ν3 = 1 rovibrational constants obtained, the inertial defect Δ3 was 0.1619724 ± 0.0000001 μÅ2.  相似文献   

7.
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   

8.
The spectrum of the ν7 band of cis-ethylene-d2 (cis-C2H2D2) has been recorded with an unapodized resolution of 0.0063 cm−1 in the 740-950 cm−1 region using a Bruker IFS 125 HR Fourier transform infrared spectrometer. By fitting 2186 infrared transitions of ν7 with a standard deviation of 0.00060 cm−1 using a Watson’s A-reduced Hamiltonian in the Ir representation, accurate rovibrational constants for ν7 = 1 state have been derived. The band center of ν7 has been found to be 842.20957 ± 0.00004 cm−1. In a simultaneous fit of 1331 infrared ground state combination differences from the present ν7 transitions, together with 22 microwave frequencies, ground state constants have been improved. The rms deviation of the ground state fit was 0.00027 cm−1.  相似文献   

9.
The Fourier transform infrared absorption spectrum of the ν12 fundamental band of ethylene-d (C2H3D) was recorded at an unapodized resolution of 0.0063 cm−1 in the 1330-1475 cm−1 region. Upper state (ν12 = 1) rovibrational constants inclusive of three rotational, five quartic, and four sextic centrifugal distortion constants were improved by assigning and fitting 1444 infrared transitions using Watson’s A-reduced Hamiltonian in the Ir representation. The present analysis yielded more higher-order upper state constants than previously reported. The rms deviation of the fit is 0.00055 cm−1. Improved ground state rovibrational constants were also determined from the combined fit of 2026 ground state combination differences (GSCD) from the assigned infrared transitions of the ν12, ν3 and ν6 bands and 21 microwave frequencies of C2H3D. The rms deviation of the GSCD fit is 0.00047 cm−1. The A-type ν12 band is centered at 1400.76262 ± 0.00004 cm−1. Local frequency perturbations were not detected in the analysis. The calculated inertial defect Δ12 is 0.20809 ± 0.00003 μÅ2.  相似文献   

10.
Unstable, short-lived BiH3 has been synthesized and investigated by rotational spectroscopy in the range 158 (J=1-0) to 1280 GHz (J=8-7). Quadrupole and spin-rotation hyperfine structures (eQq=584.676(96) MHz), and the A1A2 splitting of the K=3 ground state level, have been resolved. By merging the pure rotational data with 1764 ground state combination differences obtained from the analysis of high resolution Fourier transform infrared spectra of the ν1-ν4 bands [J. Mol. Spectrosc. (2004) (in press)] spanning J and K values up to 16 and 14, respectively, with 0?ΔK?9, the ground state rotational and centrifugal distortion constants up to octic and sextic terms for reductions A and B, respectively, have been determined. Of the reductions of the ground state rovibrational Hamiltonian, reduction B including ε rather than h3 as off-diagonal element is clearly favored. An experimental r0 structure of the very-near spherical oblate symmetric top BiH3, r(BiH)=178.82 pm and α(HBiH)=90.320°, has been deduced from the rotational constants B0=2.64160172(18) and C0=2.6010403(31) cm−1. The derived experimental re structure, re(BiH)=177.834(50) pm and αe(HBiH)=90.321(10)°, was determined. This is in excellent agreement with the most recent ab initio structure, re(BiH)=177.84 pm, and αe(HBiH)=90.12°.  相似文献   

11.
The Fourier transform infrared (FTIR) spectrum of the ν12 fundamental band of ethylene-1-13C (or 13C12CH4) was recorded with an unapodized resolution of 0.0063 cm−1 in the wavenumber region of 1360-1520 cm−1. Rovibrational constants for the upper state (ν12 = 1) up to five quartic and two sextic centrifugal distortion terms were derived for the first time by assigning and fitting a total of 879 infrared transitions using a Watson’s A-reduced Hamiltonian in the Ir representation. The root-mean-square deviation of the fit was 0.00066 cm−1. The ground state rovibrational constants were also determined by a fit of 523 combination-differences from the present infrared measurements, with a rms deviation of 0.00090 cm−1. The A-type ν12 band which is centred at 1439.34607 ± 0.00004 cm−1 was found to be relatively free from local frequency perturbations. From the ν12 = 1 rovibrational constants obtained, the inertial defect Δ12 was found to be 0.242826 ± 0.000002 μÅ2.  相似文献   

12.
The gas phase infrared emission spectrum of the A3Σ-X3Π electronic transition of SiC has been observed using a high resolution Fourier transform spectrometer. Three bands ν′ − ν″ = 0-1, 0-0, and 1-0 have been observed in the 2770, 3723, and 4578 cm−1 regions, where the 0-1 and 0-0 bands were observed for the first time. The SiC radical was generated by a dc discharge in a flowing mixture of hexamethyl disilane [(CH3)6Si2] and He. A total of 1074 rotational transitions assigned to the 0-1, 0-0, and 1-0 bands have been combined in a simultaneous analysis with previously reported pure rotational data to determine the molecular constants for SiC in the two electronic states. The principal equilibrium molecular constants for the A3Σ state are: Be = 0.6181195(18) cm−1, αe = 0.0051921(20) cm−1, re = 1.8020884(26) Å, and Te = 3773.31(17) cm−1, with one standard deviation given in parentheses. The effect of a perturbation was recognized between the ν = 4 level of X3Π and the ν = 0 level of A3Σ, and the analysis was carried out to determine the interaction parameter between the two states.  相似文献   

13.
Laser induced fluorescence spectra of HoS have been obtained using a Broida oven and a ring dye laser. Dispersed fluorescence spectra showed transitions from a common upper state, A[14.79]8.5 to the v = 0 and 1 vibrational levels of three low lying states, labelled X8.5, W[0.25]7.5 and V[0.98]7.5 (the states are labelled [10−3T0]Ω according to their energy and Ω assignment). High resolution excitation spectra were obtained for all six transitions and a rotational analysis yielded the following principal constants, in cm−1, for the X, W and V states, respectively: T0 = 0, 251.8713(31), 980.6969(37); Be = 0.121903(42), 0.121729(37), 0.122561(34); ΔG1/2 = 463.8811(46), 462.9411(45), 461.2084(127). For the A state, T0 = 14794.6987(28) cm−1 and B0 = 0.112596(29) cm−1. The three low lying states are shown to arise from the Ho2+[4f10(5I8)6s]S2− configuration in accord with Ligand Field Theory predictions. The atomic origin of each of the three low lying electronic states was determined from the observed resolved hyperfine structure.  相似文献   

14.
The microwave spectra of two isotopic species of acetyl isocyanate, 13CH3C(O)NCO and CD3C(O)NCO, were observed in order to determine the ro structure and confirmation of the molecular conformation. These isotopic species were prepared by reacting acetyl-2-13C-chloride or acetyl-d3 chloride with sliver cyanate. The rotational spectra of A-level in 26.5-60.0 GHz region have been observed by Stark-modulated microwave spectrometer. Some absorption lines in E-level were observed in 13CH3C(O)NCO. The rotational constants in the ground vibrational state were determined to be A = 10654.8(18), B = 2177.32(2), and C = 1827.65(2) MHz for 13CH3C(O)NCO, and A = 9713.90(6), B = 2042.04(2), and C = 1722.78(2) MHz for CD3C(O)NCO, respectively. The values of ΔI (= Ic − Ia − Ib) of the 13C species (−3.024(13) uÅ2) and the d3 species (−6.163(3) uÅ2) indicate that the molecule has Cs symmetry. The rs coordinates of the carbon atom in the methyl group were determined to be |a| = 2.183(3), |b| = 0.706(9), and |c| = 0.080(87) Å. The determined coordinates were in agreement with those calculated for the cis form, in which the carbonyl group is eclipsed by the NCO group. The six structural parameters of the cis form were adjusted by fitting to the observed rotational constants. The observed rotational constants of the cis form were in better agreement with those calculated using the QCISD/6-31G (d, p) level rather than those calculated using the MP2/6-31G (d, p) level. The barrier of internal rotation of the methyl group was determined as 4.283(16) kJ mol−1 in 13CH3C(O)NCO. The structural tendencies and the relationship between RNC and 14N quadrupole coupling constants (χcc) were discussed.  相似文献   

15.
EPR study of the Cr3+ ion doped l-histidine hydrochloride monohydrate single crystal is done at room temperature. Two magnetically inequivalent interstitial sites are observed. The hyperfine structure for Cr53 isotope is also obtained. The zero field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular rotations and the parameters are: D=(300±2)×10−4 cm−1, E=(96±2)×10−4 cm−1, gx=1.9108±0.0002, gy=1.9791±0.0002, gz=2.0389±0.0002, Ax=(252±2)×10−4 cm−1, Ay=(254±2)×10−4 cm−1, Az=(304±2)×10−4 cm−1 for site I and D=(300±2)×10−4 cm−1, E=(96±2)×10−4 cm−1, gx=1.8543±0.0002, gy=1.9897±0.0002, gz=2.0793±0.0002, Ax=(251±2)×10−4 cm−1, Ay=(257±2)×10−4 cm−1, Az=(309±2)×10−4 cm−1 for site II, respectively. The optical absorption studies of single crystals are also carried out at room temperature in the wavelength range 195-925 nm. Using EPR and optical data, different bonding parameters are calculated and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are: B=636, C=3123, Dq=2039 cm−1, h=1.46 and k=0.21, respectively.  相似文献   

16.
The pure rotational spectrum of TiS in its X3Δr ground state has been measured using millimeter-wave direct-absorption techniques in the frequency range of 313-425 GHz. This free radical was created by the reaction of titanium vapor, produced in a high-temperature Broida-type oven, with H2S. Eight to ten rotational transitions were recorded for the main titanium isotopologue, 48TiS, in the v = 0 and v = 1 levels, as well as for the v = 0 state of 46TiS, observed in natural abundance (48Ti:46Ti = 74:8). All three Ω components were observed in almost every recorded transition, with no evidence for lambda-doubling. The data were fit with a Hund’s case(a) Hamiltonian, and rotational, spin-orbit, and spin-spin constants were determined, as well as equilibrium parameters for 48TiS. Relatively few fine structure parameters were needed for the analysis of TiS (A, AD, and λ), unlike other 3d metal species. The rotational pattern of the three fine structure components suggests the presence of a nearby excited 1Δ state, lying ∼3000 cm−1 higher in energy. From the equilibrium parameters, the dissociation energy for TiS was estimated to be ∼5.1 eV, in reasonable agreement with past thermochemical data.  相似文献   

17.
The absorption spectrum of the ν6 band of C2H3D centered near 1125.27674 cm−1 in the 1100-1250 cm−1 region was recorded with an unapodized resolution of 0.0063 cm−1 using a Fourier transform infrared (FTIR) spectrometer. A total of 947 infrared transitions of the A-B hybrid-type band were assigned and fitted to upper-state (ν6 = 1) rovibrational constants using a Watson’s A-reduced Hamiltonian in the Ir representation up to eighth-order centrifugal distortion terms. The b-type infrared transitions of the band were analyzed for the first time. The root-mean-square deviation of the fit was 0.00062 cm−1. The ground-state rovibrational constants up to eighth-order terms were also obtained by a fit of 617 combination differences from the present infrared measurements, simultaneously with 21 microwave frequencies with a root-mean-square deviation of 0.00055 cm−1. From this work, the upper-state (ν6 = 1) and ground-state constants of C2H3D were derived with the highest accuracy, so far. The a- and b-type transitions of the hybrid ν6 band were found to be relatively free from local frequency perturbations. The ratio of the a- to b-type vibrational dipole transition moments (μa/μb) was found to be 1.05 ± 0.10. From the ν6 = 1 rovibrational constants obtained, the inertial defect Δ6 was calculated to be 0.3570 ± 0.0008 μÅ2.  相似文献   

18.
The Fourier transform gas-phase infrared spectrum of pyrrole, C4H5N, has been recorded with a resolution of ca. 0.003 cm−1 in the 900-1500 cm−1 spectral region. Four fundamental bands, ν8(A1; 1016.9 cm−1), ν23(B2; 1049.1 cm−1), ν7(A1; 1074.6 cm−1), ν20(B2; 1424.4 cm−1) and the overtone band 2ν16(A1; 962.7 cm−1) have been analysed using the Watson model. The ν8 and 2ν16 bands are unperturbed; the ν7 and ν23 bands are locally perturbed, while the ν20 band is globally perturbed by weak c-Coriolis resonance. Upper state vibrational term values, and rotational and centrifugal distortion constants, have been obtained from fits using S-reduction and Ir-representation as well as A-reduction and IIIr-representation. A set of ground state rotational and centrifugal distortion constants using A-reduction was obtained from a simultaneous fit of ground state combination differences from all five bands and previous microwave and millimetre-wave data.  相似文献   

19.
The gas phase far-IR spectrum of the ν20 (A″, 367.88 cm−1) and ν21 (A″, 311.28 cm−1) bands of 1,2,4-triazine, a five membered ring having the point group Cs, has been studied at a resolution ranging from 0.002 to 0.003 cm−1. From the MW spectrum 58 transitions in the ν20 level and 64 in the ν21 level have been assigned. The ν20 and ν21 modes which are due to non-planar motions of the ring system are found to be nearly unperturbed. From a simultaneous analysis of IR and MW transitions band centers, rotational constants, and the quartic centrifugal distortion constants , and δK have been obtained using the Watson Hamiltonian, A-reduction, IIIr-representation.  相似文献   

20.
The pure rotational spectrum of the TiCl+ ion in its X3Φr ground state has been measured in the frequency range 323-424 GHz, using a combination of direct absorption and velocity modulation techniques. The ion was created in an AC discharge of TiCl4 and argon. Ten, eleven, and nine rotational transitions were recorded for the 48Ti35Cl+, 48Ti37Cl+, and 46Ti35Cl+ isotopomers, respectively; fine structure splittings were resolved in every transition. The rotational fine structure pattern was irregular with the Ω = 4 component lying in between the Ω = 2 and 3 lines. This result is consistent with the presence of a nearby 3Δr state, which perturbs the Ω = 2 and 3 sub-levels, shifting their energies relative to the Ω = 4 component. The data for each isotopomer were analyzed in a global fit, and rotational and fine structure parameters were determined. The value of the spin-spin constant was comparable to that of the spin-orbit parameter, indicating a large second-order spin-orbit contribution to this interaction. The bond length established for TiCl+, r0 = 2.18879 (7) Å, is significantly shorter than that of TiCl, which has r0 = 2.26749 (4) Å. The shorter bond length likely results from a Ti2+Cl structure in the ion relative to the neutral, which is thought to be represented by a Ti+Cl configuration. The higher charge on the titanium atom shortens the bond.  相似文献   

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