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1.
The microwave spectrum of bicyclo[2.1.1]hexan-5-one has been analyzed, resulting in a total dipole moment of 3.18 ± 0.02 D with an orientation of 1.7 ± 1.7° with respect to the carbonyl bond axis. This dipole moment is about 0.3 D larger than that of most other carbonyl compounds, but it is reasonably comparable to the even higher values which have been reported for bicyclo[2.1.1]hexan-2-one (3.35 ± 0.02 D) and for cyclopentanone (3.25 ± 0.02 D). The rotational constants for the ground vibrational state are A = 4448.347 ± 0.011, B = 2693.349 ± 0.008, and C = 2673.300 ± 0.006, the uncertainties being standard deviations determined from a least-squares fit. 相似文献
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P. J. Mjberg W. M. Ralowski S. O. Ljunggren J. E. Bckvall 《Journal of Molecular Spectroscopy》1976,60(1-3)
The microwave spectrum of 6-thiabicyclo[3.1.0]hexane (cyclopentene sulfide) has been measured in the region 26,500-40,000 MHz. The experimental data are consistent with a single stable conformation. Furthermore, these data can only be satisfactorily explained by assuming that this conformation is the boat form. Rotational constants were obtained, both for the ground state and two excited vibrational states, while centrifugal distortion coefficients were obtained for the ground state and one excited vibrational state. The ground state rotational constants found were A0 = 5026.243 ± 0.003 MHz, B0 = 2833.813 ± 0.003 MHz, and C0 = 2411.679 ± 0.03 MHz. For the ground state of the molecule, the electric dipole moment components were found to be μa = 1.800 ± 0.012 D and μc = 1.155 ± 0.024 D, yielding a total dipole moment μ = 2.139 ± 0.027 D. 相似文献
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The microwave spectra of the normal and four monosubstituted 13C isotopic species of bicyclo[3.1.0]hex-2-ene have been observed and analyzed. For the normal species the rotational constants (in megahertz) are: Λ = 6306.121 ± 0.006, B = 4516.667 ± 0.004, C = 3208.823 ± 0.002. From the complete data set, a partial rs heavy-atom structure has been obtained as well as a complete effective structure. The rs distances are found to be C1C5 = 1.521 ± 0.001 Å, C1C2 = 1.494 ± 0.010 Å, C5C6 = 1.482 ± 0.006 Å, C1C6 = 1.522 ± 0.007 Å. The overall effective structure shows the five-membered ring to be only slightly nonplanar (by ca. 6°), and the three-membered ring to be rather sharply inclined with respect to the five-membered ring (dihedral angle C1C5C6-C1C5C4 = 113.5°). Dipole moment measurements for the symmetryless molecule yielded values of |μa| = 0.166 ± 0.009, |μb| = 0.209 ± 0.015, |μc| = 0.119 ± 0.001, |μT| = 0.292 ± 0.012 D. 相似文献
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M.A. Martin T. Masiello J.W. Nibler A. Weber T.A. Blake 《Journal of Molecular Spectroscopy》2010,262(1):42-48
Infrared spectra of bicyclo[1.1.1]pentane (C5H8) have been recorded at a resolution (0.0015 cm−1) sufficient to resolve for the first time individual rovibrational lines. This initial report presents the ground state constants for this molecule determined from the detailed analysis of three of the ten infrared-allowed bands, ν14(e′) at 540 cm−1, ν17 (a2″) at 1220 cm−1, ν18(a2″) at 832 cm−1, and a partial analysis of the ν11(e′) band at 1237 cm−1. The upper states of transitions involving the lowest frequency mode, ν14(e′), show no evidence of rovibrational perturbations but those for the ν17 and ν18 (a2″) modes give clear indication of Coriolis coupling to nearby e′ levels. Accordingly, ground state constants were determined by use of the combination-difference method for all three bands. The assigned frequencies provided over 3300 consistent ground state difference values, yielding the following constants for the ground state (in units of cm−1): B0 = 0.2399412(2), DJ = 6.024(6) × 10−8, DJK = −1.930(21) × 10−8. For the unperturbed ν14(e′) fundamental, more than 3500 transitions were analyzed and the band origin was found to be at 540.34225(2) cm−1. The numbers in parentheses are the uncertainties (two standard deviations) in the values of the constants. The results are compared with those obtained previously for [1.1.1]propellane and with those computed at the ab initio anharmonic level using the B3LYP density functional method with a cc-pVTZ basis set. 相似文献
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The He I photoelectron spectrum of CSe2 has been recorded and four of the bands observed assigned to ionization from valence shell levels that correlate well with those found for CO2 and CS2. Weak bands in the spectra of CS2 and CSe2 are assigned to shake-up processes in which electronic excitation of the ion accompanies ionization. 相似文献
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Determination of the anion O-3 geometry by Franck-Condon simulations of its photoelectron spectrum 总被引:2,自引:1,他引:1
A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectroscopy of the anion O-3. Geometry optimization and harmonic vibrational frequency calculations have been performed on the (X~)1A1 state of O3 and (X~)2B1 state of O-3. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of O-3. The theoretical spectrum obtained by employing CCSD(T)/6-311+G(2d,p) values are in excellent agreement with the observed one. In addition, the equilibrium geometry parameters, re(OO)= 0.135 5±0.000 5 nm and θe(O-O-O) =114.5±0.5°, of the (X~)2B1 state of O-3, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation. 相似文献
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K. V. Berezin V. V. Nechaev M. K. Berezin N. F. Stepanov S. V. Krasnoshchekov 《Optics and Spectroscopy》2014,117(3):366-373
The anharmonic vibrational IR and Raman spectra of the bicyclo[1.1.0]butane molecule have been calculated in the range of up to 4000 cm?1 using a numerical and analytical realization of the van Vleck second-order operator perturbation theory. Cubic and quartic force constants in normal coordinates, as well as cubic surfaces of the dipole moment and polarizability, have been found by numerical differentiation of the corresponding first and second derivatives calculated by the MP2/cc-pVTZ quantum-mechanical method. In order to increase the prediction accuracy of vibrational transitions, corresponding harmonic frequencies have been obtained by the CCSD(T)/cc-pVTZ high-precision quantum mechanical method. The anharmonic intensities of the IR and Raman spectra have been calculated using canonical transformations of the operators of the dipole moment and polarizability expanded into a Taylor series around the equilibrium configuration. The assignment of experimental vibrational bands in the IR and Raman spectra has been analyzed. It has been shown that the anharmonic calculation based on the above-described procedure of combining more exact harmonic frequencies with the anharmonic force field obtained with a more economical method makes possible the reliable interpretation of the majority of spectral bands, including Fermi and Darling-Dennison resonances. 相似文献
10.
The microwave spectrum of 3,6-dioxabicyclo[3.1.0.]hexane has been obtained. The rotational lines of one ring conformation only have been observed and assigned. Ground state rotational constants are A0 = 6287.302 ± 0.011 MHa, B0 = 4683.546 ± 0.008 MHz, and C0 = 3358.517 ± 0.089 MHz. The diploe moment components obtained from Stark effect measurements are μa = 0.276 ± 0.010 D and μc = 2.47 ± 0.04 giving μ = 2.485 ±0.040 for the dipole moment of the molecule. The rotational constants and dipole moment components obtained experimentally can be satisfactorily explained only if the boat form is the most stable ring conformation. 相似文献
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D. Dougherty R.L. Blankespoor S.P. McGlynn 《Journal of Electron Spectroscopy and Related Phenomena》1979,16(3):245-258
The HeI photoelectron spectra (UPS) of several bicyclo [2.2.1] heptane-2,3-diones and bicyclo[2.2.1] hept-5-ene-2,3-diones are presented. Interpretations are based on CNDO/s computations and empirical correlations. The n+ orbital of the two carbonyl groups interacts strongly with, the π orbital of the 5-ene moiety in bicyclo[2.2.1]hept-5-ene-2,3-diones. This interaction is dominantly “through-bond”, there being little or no direct (i.e. “through-space”) overlap. The net result is that insertion of 5-ene unsaturation increases the splitting of the n+ and n? orbitals from ca. 1.9 to ca. 2.4 eV. Finally, the π* (CO) ← n+ electronic absorption spectra of the [5-ene] -compounds, which are geometrically suited to an investigation of π/π* (CO) interactions, suggest that such mixing is negligible. 相似文献
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Patrick Brant 《Journal of Electron Spectroscopy and Related Phenomena》1984,33(2):153-162
The C and N 1s spectra of methylisocyanide gas have been recorded. Two resolvable peaks of equal intensity are observed in the C 1s spectrum. Using the equivalent-cores approximation and thermochemical data, together with MNDO MO calculations and the point-charge potential model, the lower-binding-energy C 1s line is assigned to photo-emission from the isocyano carbon. The strong satellites which have been observed in the spectra of coordination complexes of alkyl and aryl isocyanides are not observed in the spectra of the free molecule. Comparisons of the point-charge-potential-corrected binding energies for C 1s and N 1s photoemissions from CH3NC and its isomer CH3CN with those for a host of other molecules show that photoemissions from the internal atoms in these molecules are accompanied by substantially less than average relaxation energies. These smaller relaxation energies can be understood using valence-bond theory. 相似文献
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本文基于MOLPRO软件包使用从头算方法计算了星际分子H2S及其阳离子H2S+的势能面及光电子能谱.首先,在(U)CCSD/cc-pVQZ理论水平下获取了H2S沿法线坐标展开的势能面,势能面直观描述了不同振动模式耦合对分子能量变化的影响,S-H键的非对称伸缩振动和面内弯曲振动共同作用使得系统势能变化范围明显变大.振动多组态相互作用方法被用来计算非谐振动频率和振动光谱,计算结果显示,倍频和组合频之间出现了强烈的费米共振,使得相应波段处的红外强度显著增强.最后,使用拉曼波函数和收缩不变Krylov子空间方法首次计算了H2SΧ1A1→H2S+ X2B1的光电子能谱.此项研究有助于进一步理解星际分子的内部结构,并为实验研究及星际观测提供参考. 相似文献
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P. Bischof R. Gleiter M.J. Kukla L.A. Paquette 《Journal of Electron Spectroscopy and Related Phenomena》1974,4(3):177-184
The photoelectron spectra of tricyclo[3.3.0.02,6]octene (1) and tricyclo[3.3.0.02,6]octane (2) have been recorded. The first bands in these spectra are correlated with orbitals which are linear combinations of the Walsh orbitals and of the olefinic π-orbital. This assignment is based on a zero differential overlap molecular orbital model as well as on the results of extended Hückel calculations. The resonance integral <π|H|W > for 1 is found to be ?1.34 eV. 相似文献
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Stephen Bomar Elliott Bay H.-G Kraft J.W Bevan 《Journal of Molecular Spectroscopy》1981,87(2):482-489
The R band (26.5–40 GHz) microwave spectrum of 2,4-dioxabicyclo[3.1.0]hexan-3-one is reported. Rotational constants for the ground vibrational state of the common 12C41H416O3 and 13C1, 13C6 isotopically substituted species (the latter observed in natural abundance) have been evaluated. In addition rotational constants of the VB = 1 to VB = 5 quanta associated with the bending vibration of the five membered ring have been determined. A partial rs structure has been calculated: , . With certain assumed molecular information a least squares fit yields the following parameters: , , . 相似文献
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D. Robert Lloyd Peter J. Roberts Ian H. Hillier Ian C. Shenton 《Molecular physics》2013,111(5):1549-1556
He(I), He(II) and variable temperature Ne(I) photoelectron spectra of sulphur trioxide are reported. All six of the expected ionic states have been detected and assigned; the assignment differs from a previous one. Ab initio calculations in a medium basis set have been carried out and spectral intensities have been calculated; agreement between the calculations and the spectra is good. The calculations show a substantial S(3d) character in the S-O bond, and the spectra are consistent with this. 相似文献