共查询到20条相似文献,搜索用时 15 毫秒
1.
The equilibrium geometries, excitation energies, force constants and vibrational frequencies for seven low-lying electronic states X 1A 1, 1B 1, 3B 1, 1A 2, 3A 2, 1B 2 and 3B 2 of dichlorocarbene CCl 2 have been calculated at the MRSDCI level with a double-zeta plus polarization basis set. Our calculated equilibrium geometry for the X 1A 1 state, excitation energy for X 1A 1 → 1B 1 and vibrational frequencies for the X 1A 1 and 1B 1 states are in good agreement with experimental data. The electronic transition dipole moments, oscillator strengths for the 1B 1 → X 1A 1 and 1B 2 → X 1A 1 transitions, radiative lifetimes for the 1B 1 and 1B 1 states are calculated using MRSDCI wavefunctions, predicting results in reasonable agreement with experiment. 相似文献
2.
The 1 2B 1(X 2B 1), 1 2B 2, 1 2A 1, 1 2A 2, 2 2B 2, and 2 2A 1 states of the ion were studied using CASPT2 and CASSCF methods. Calculations suggest that one should consider the 3 2A′ state instead of 2 2B 2. The CASPT2 T0 calculations predict the energy ordering of 1 2B 1(X 2B 1), 1 2B 2, 1 2A 1, 1 2A 2, 3 2A′, and 2 2A 1, which is in line with the experimental results by Pradeep and Shirley. The CASPT2 T0 values for the 1 2B 2, 1 2A 2, 3 2A′, and 2 2A 1 states are close to the experimental values. The F-loss and H-loss dissociation processes were studied at the CASPT2//CASSCF level. The energy levels of low-lying states of are compared. 相似文献
3.
Ab initio calculations were performed to study the molecular structures and the vibrational levels of the low-lying ionic states ( 2B 1, 2A 1 and 2B 2) of hydrogen sulphide. The equilibrium molecular structure and the vibrational analysis of these states are presented. The normal vibrational calculations at the RHF level and more extensive calculations at the SDCI level using the explicit vibrational Hamiltonians were used for the vibrational analysis. The theoretical ionization intensity curves including the vibrational structures of these ionic states are also presented and compared with the photoelectron spectrum. The results show that the global shape of the potential energy surface has to be taken into consideration in order to analyze the 2A 1 and 2B 2 states. A new assignment of the photoelectron spectra of H 2S is proposed. 相似文献
4.
Relative emission spectra for the bent to linear, CO 2( 1B 2)---CO 2(X 1Σ +g) transitions have been calculated using the model: harmonic oscillator, symmetric-top wavefunctions and energy levels for CO 2( 1B 2); first-orer Fermi resonance vibrational wavefunctions and energy levels for CO 2(X 1Σ +g); a Boltzmann distribution of vibrational and rotational states in CO 2( 1B 2); and a constant electronic transition moment. With the literature CO 2( 1B 2) molecular structure, spectra calculated using this model show characteristics similar to the low-temperature chemiluminescence from the combination of atomic oxygen and carbon monoxide. The calculated spectra account for experimental band positions to wavelengths of 570 nm and the weak dependence of the spectra on temperature over the range 206–353 K. The latter result was obtained from a CO 2( 1B 2) bending fundamental of 600 cm −1. The calculated spectra also show a violet-shift in intensity and an attenuated band structure at higher temperatures. The magnitude of these effects depends on the CO 2( 1B 2) force constants and not on the CO 2( 1B 2) molecular structure. 相似文献
5.
The encounter complex C 2H 4…ClF was isolated by using a fast-mixing nozzle before chemical reaction could occur between the components and was characterised by Fourier-transform microwave spectroscopy. Rotational constants, centrifugal distortion constants, Cl nuclear quadrupole constants and Cl spin-rotation constants were determined for the isotopomers C 2H 4… 35ClF and C 2H 4… 37ClF. The complex has C 2v symmetry with the ClF subunit perpendicular to the plane of C 2H 4 and oriented so that Cl is closer to C 2H 4. Both the centrifugal distortion constant Δ J and the Cl nuclear quadrupole coupling constants indicate that the complex is relatively weakly bound and it is concluded that the interaction between the subunits is largely electrostatic in origin. 相似文献
6.
应用量子化学密度泛函理论研究了燃煤烟气中As和AsO与O_2均相生成As_2O_3的反应机理。首先计算确定了各反应物、中间体、过渡态和产物的结构和能量,然后运用热力学和动力学方法对As_2O_3均相生成过程进行分析。结果表明,由As和AsO与O_2均相生成As_2O_3的最大反应能垒分别为32.9和157.2kJ/mol,在烟气中由As转化为As_2O_3更为容易进行。在500-1900 K下,各反应的正逆反应速率常数均随温度的提高而增大,但不同反应过程受温度影响的程度不同。As与O_2反应生成AsO和AsO_2的两个反应过程的平衡常数在所研究的温度范围内均大于10~5,能完全反应,可以认为是单向反应。AsO与O_2反应生成AsO_2的过程平衡常数在所研究的温度范围内小于10~5,反应不完全,转化率低。AsO与AsO_2生成As_2O_3(D3H)构型的平衡常数极低,反应难以进行,而生成As_2O_3(GAUCHE)构型反应能垒低,可自发进行。 相似文献
7.
The mechanism of the H 2NO( 2B 1)→NO( 2Π)+H 2 reaction has been examined using ab initio molecular orbital methods. Ground-state and first-excited-state potential surfaces were plotted at the FOCI/cc-pVTZ level of theory as functions of two appropriate internal degrees of freedom. A conical intersection was found on the Cs pathway that is symmetric with respect to the plane perpendicular to the molecular plane of C2v H 2NO( 2B 1). It is therefore considered that trajectories that start from H 2NO( 2B 1) towards the product region detour around the conical intersection, pass through the neighborhood of the transition state that is located at the saddle point on the Cs pathway, and finally reach the products, NO( 2Π)+H 2. Thus we can explain the mechanism of the H 2NO( 2B 1)→NO( 2Π)+H 2 reaction, which has remained unclear to date. 相似文献
8.
We have combined the high sensitivity of the ICLAS technique with the rotational cooling effect of a slit jet expansion in order to observe and to understand the visible and near infrared NO 2 spectrum. By this way, an equivalent absorption pathlength of several kilometers through rotationally cooled molecules has been achieved. Due to the vibronic interaction between the two lowest electronic states,
2A 1 and à 2B 2, this spectrum is vibronically dense and complex. Moreover, the dense room temperature rotational structure is perturbed by additional rovibronic interactions. In contrast, the rotational analysis of our jet cooled spectrum is straightforward. The NO 2 absorption spectrum is vanishing to the IR but, owing to the high sensitivity of the ICLAS technique, we have been able to record the NO 2 spectrum down to 11200 cm −1 with a new Ti:sapphire ICLAS spectrometer. As a result 249 2B 2 vibronic bands have been observed (175 cold bands and 74 hot bands) in the 11200–16150 cm −1 energy range. Due to the cooling effect of the slit jet we have reduced the rotational temperature down to about 12 K and at this temperature the K = 0 subbands are dominant. Consequently, we have analysed only the K = 0 manifold for N 7 of each vibronic band. The dynamical range of the band intensities is about one thousand. Due to the strong vibronic interaction between the
2A 1 and à 2B 2 electronic states, we observed not only the a 1 vibrational levels of the à 2B 2 state but also the b 2 vibrational levels of the
2A 1 state interacting with the previous ones. By comparison with the calculated density of states, we conclude that we have observed about 65% of the total number of 2B 2 vibronic levels located in the studied range. However, there are more missing levels in the IR because of the weakness of the spectrum in this range. The correlation properties of this set of vibronic levels have been analysed calculating the power spectrum of the absorption stick spectrum which displays periodic motions: the dominant period, at 714 ± 20 cm −1, corresponds to the bending motion of the à 2B 2 state. The other observed periods remain unassigned. In contrast the next neighbor spacing distribution (NNSD) shows a strong level repulsion, i.e. a manifestation of quantum chaos. These two observations, apparently contradictory, can be rationalized as follows: the short time dynamics, for t < 10 −12 s, is “regular” while for longer times the dynamics becomes “chaotic”. We suggest that this behavior may be observed directly with a pump and probe fs laser experiment. 相似文献
9.
A complete vibrational analysis has been carried out for germylacetylene and germylacetylene- d3 molecules and a set of molecular constants, i.e. kinetic constants and potential constants, is reported. The physical understanding of the nature of the potential constants and kinetic constants in molecules leads to a stringent application of provisions of group theoretical technique, introduced by Wilson in the study of molecular vibrations. This procedure is applied here to the evaluation of mean amplitudes of vibration. Coriolis coupling constants and centrifugal distortion constants of these cases, with highly satisfactory results. The values of Coriolis coupling constants and centrifugal distortion constants are in good agreement with the observed values for the germylacetylene molecule showing the significance of the procedure adopted in the present study. 相似文献
10.
The excited state geometries of the metal-metal quadruply bonded compounds Mo 2X 4(PMe 3) 4 (X = Cl, Br or I) have been studied by means of resonance Raman and absorption spectroscopy. A fit of the parameters of a simple theoretical model to the experimental data indicates that the metal-metal bond increases some 10 pm on excitation to the 1B 2 (δδ *) state, whereas other geometric changes are small. Furthermore, the phenomenological lifetime factor of the excited state, Γ, is found to be dependent on the vibrational quantum number, ν, of this state. 相似文献
11.
Numbers and densities of vibrational states of non-rotating polyatomic molecules are calculated by a simplified model which accounts for Morse anharmonicities of stretching and for generalized empirical stretch-bend couplings of bending modes. At energies above the dissociation limit, adiabatic channel maxima restrict the molecular phase space. The model is applied to the NO 2(
2A 1), NO 2(Ã 2B 2), and H 3+ systems for which satisfactory agreement with the available experimental or calculational results is obtained. 相似文献
12.
The pure rotational Raman spectra of C 214N 2 and C 215N 2 have been recorded photographically using a 3-metre spectrograph with a reciprocal linear dispersion of 1.4 cm −1 mm −1 at 488.0 nm and analysed to give the rotational and centrifugal distortion constants for both species. Corrections were applied to compensate for the effect of molecules in excited vibrational states on the pure rotational spectra. Comparisons are made with previous infrared vibration—rotational studies on these species and with previous Raman studies on C 214N 2. The following bond lengths were calculated: r0(C---N) = 116 ± 1 pm; r0(C---C) = 138 ± 2 pm. 相似文献
13.
Various P 2O 2 planar isomers are investigated by molecular orbital calculations. Cyclic
( 1A g) is predicted to be more stable than OPOP ( 3A″-cis) and OPPO ( 1A g-trans) by 5.6 and 23.1 kcal/mol, respectively. The dimerization energy of 2PO→cyclic OPOP lies around 55 kcal/mol; the asymmetrical conformations OPOP and symmetrical OPPO are also bound. The computed vibrational frequencies and corresponding absorption intensities (derived at the SCF level) should help future experimental characterizations of these P 2O 2 isomers. 相似文献
14.
Resonance fluorescence spectra of CF 2( 1B 1, 040, K' = 9) excited at 253 7 nm have been observed in the photolysis of C 2F 4 using a low-pressure mercury lamp. At low C 2F 4 pressures, the spectra with a series of doublet hands from 254 to 400 nm were consistent with the transitions from 1B 1, 040, K'=9 to 1A 1, 0 v'20, K' = 8, 10, and also to 1A 1, 1 v'20, K' = 8, 10 The appearance of doublet bands (Δ K = ±1) provides clear evidence that the transition is of the perpendicular type. 相似文献
15.
Coriolis coupling constants have been calculated from force field computations and used to evaluate the inertial defect of 1,1-dichlorodifluoroethylene, 1,1-dichlorodibromoethylene and 1,1-difluorodibromoethylene. The inertial defect values for the ground vibrational state of 1,1-C1 2C=CF 2 = 0.2450, 1,1-Cl 2C=CBr 2 = 0.3740 and 1,1-F 2C=CBr 2 = 0.4190 amu Å 2 show corrrespondence with the observed values of similar ethylene-type molecules. 相似文献
16.
采用高温固相法制备了La_(2.4)Mo_(1.6)O_8∶Yb~(3+),Er~(3+)荧光粉。通过X射线衍射(XRD)和上转换发射光谱对样品进行了相结构和发光性质表征。XRD实验结果表明:合成的样品为面心立方萤石结构(Fm-3m)的La_(2.4)Mo_(1.6)O_8相。在980 nm红外光激发下,La_(2.4)Mo_(1.6)O_8∶Yb~(3+),Er~(3+)荧光粉发出分别来自Er~(3+)离子的~2H1_(1/2)→~4I_(15/2)、~4S_(3/2)→~4I_(15/2)跃迁的绿光(主峰为548和529 nm)和~4F_(9/2)→~4I_(15/2)跃迁的红光(主峰为670 nm)。进一步地,对样品中可能的上转换发光机制进行了讨论。 相似文献
17.
Ab initio configuration interaction calculations with a double zeta basis augmented by polarisation functions have been carried out for all the lowest singlet and triplet states of S 2N 2 and (SN) 2) - a unit of the polymer (SN) x. The results satisfactory account for the UV-absorption spectrum of S 2N 2 which is probably dominated by 1B 2u. There are low-lying singlet and triplet states for (SN) 2, and one of these a σσ* triplet seems likely to be the polymerisation precursor. 相似文献
18.
Absolute rate constants for the removal of CH 2 (ã 1A 1) by Ar, NO and H 2 have been measured over the temperature range 295–431 K using laser flash kinetic absorption spectroscopy. For NO and H 2, no marked temperature dependence is observed. For Ar, the rate constants increase by some 50% over this range and the results are discussed in terms of a theoretical model which relates the removal rate constants to the fractional population of CH 2 (ã 1A 1) in states perturbed by nearby triplet levels. 相似文献
19.
A three-dimensional potential energy function has been calculated for the X 1Σ +g state of NO +2 from ab initio MRD-CI data. With this PE function, converged vibrational calculations have also been performed for ten vibrational states, with the aid of a computer program developed in the present work for this purpose. The calculated harmonic frequencies, vibrational term values and rotational constants are in good agreement with experimental data. 相似文献
20.
IR spectroscopy was coupled with the matrix isolation technique to study the molecular complex formed between C 3O 2 and HCl and its photodissociation. The vibrational frequencies of the complex were compared with those of HCl and C 3O 2 monomers. For C 3O 2, a bent structure was characterized in the solid environment. The vibrational frequencies were calculated in the 4000–400 cm−1 range using an ab initio method at the MP2/6-31G** level for the most stable complex; these frequencies describe the hydrogen interaction with the central carbon atom of C3O2 (T complex). The measured shifts between the vibrational mode frequencies of the complex and monomers were in good agreement with the calculated values. Broad-band UV irradiation ( > 230 nm) of the T complex leads preferentially to ketene chloride and carbon monoxide. Ketene chloride formation can be explained by the reaction between HCl and the carbene C2O, which results from photo-dissociation at the C=CO bond of C3O2. 相似文献
|