首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Vertical ionization potentials (VIP's) have been calculated for HCNO, HNCO, HOCN, and HN3, using Rayleigh—Schrödinger perturbation theory (RSPT) to determine corrections to Koopmans' Theorem. The calculated VIP's are used to resolve discordances between previous assignments of the PE spectra of HCNO, HNCO, and HN3. Very little is known about HOCN. The present work contains predicted VIP's for this molecule, which it is hoped will aid in its identification in the laboratory. A diagram is presented correlating the VIP's of the isoelectronic series N2O, HN3, HOCN, HNCO, HCNO, and CO2. It is shown that the variation in the magnitudes of the VIP's associated with the ionization of π electrons, and in the splittings induced in these VIP's by deviations from a linear geometry, can be accounted for qualitatively using a simple Hückel model.  相似文献   

2.
A comparative study is made of four three-parameter semiempirical potential energy functions for 32 electronic states of diatomic molecules and their ions:n 2:X1gS g + ,B 3πg,A 3 gSu,C 3 u,B′ 3 gSu.a 1 πg, a′gS u ? ,Ω 1δu N 2 + :X 2 gS g gS +A 2 π,C 2 gS u + ,B 2 gS u + CO:X1gS+,a 3 π, a′3 gSu,e 3 gS?,d 3gD1,A 1π CO+:X2gS+,A 2 π,B 2gS+ O2:X3gS g ? ,B 3 gSu,c 1 gS u ? ,b 1gS g s ,a 1 δg,c 3 δu O 2 + :X 2πg,A 2 πg, a1 πg,b 4 gS g ? A program for numerically integrating the radial Schrödinger equation by the Cooley method is worked out. Certain additional units are introduced to conserve computer time. The resulting vibrational levels are compared with the experimental levels for all the electronic states studied. It is concluded on the basis of this analysis that it is not possible to describe equally well all the electronic states of various molecules on the basis of any single three-parameter potential function. A method for choosing a potential function for describing some particular electronic state of a diatomic molecule is proposed.  相似文献   

3.
A full vibrational analysis was recently made for the H3N+CH2CH2N+H3 ion, on the basis of infrared measurements, and a partial vibrational assignment proposed1. The observed fundamentals were interpreted In terms of a C2h, symmetry for the ion. There are thirty-six fundamentals (r - llag + 8Au + 7Bg + 10Bu; Ag and Bg Raman-active only; Au and Bu infrared-active only). In addition to the eighteen infrared-active vibrations, a number of bands was observed which were assigned as formally forbidden Raman-active modes, excited by strong hydrogen bonding causing departure from the exact site symmetry of the species.  相似文献   

4.
Results of ab initio calculations of potential-energy curves for 20 singlet and 20 triplet valence states of oxygen with configuration interaction taken into account in the 6-31G basis are presented. Transition dipole moments of triplet-triplet (13ΠgB 3Σ u ? , 13ΠgA 3Σ u + , 13ΠgA3Δu, B 3Σ u ? X 3Σ g ? , 23Πu ← 13Π g, 23Σ g ? B 3Σ u ? , 13ΠuX 3Σ g ? , 23ΠuX 3Σ g ? , 23Π gA3Δu, 33ΠgA3Δ u, 23Δu ← 23Πg, 33ΠgB 3Σ u ? , and 23ΠgA 3Σ u + ) and singlet-singlet (21Σ g + ← 21Πu, 21Πu ← 11Π g, 1Πu ← 21Δg, 11Πgc 1Σ u ? , 1Πub 1Σ g + , 11Δ ua 1Δg, 21Πua 1Δg, 21Δg ← 11Δu, 1Π ua 1Δ g, 11Πub 1Σ g + , 21Πg ← 11Πu, 21Π gc 1Σ u ? , 11Δ u ← 11Π g, f′Σ u + b 1Σ g + , 21Σ g + f1Σ u + , 31Πg ← 11Δu) radiative transitions are calculated as functions of internuclear separation. The possibility of observing these transitions under experimental conditions is discussed.  相似文献   

5.
6.
A high resolution grating spectrometer and a hollow-cathode lamp were used to study the relative intensities for lines of the transition B2Σ+uX2Σ+g of the ion N+2. Mulliken's formulae are obeyed with a precision of better than 2% for N?30, except for the first two lines, for which the relative intensities of the P lines are 2.5% greater than Mulliken's values and the relative intensities of the R lines 2.5% lower. The differences in the positions of the doublets for the first lines increase linearly (γ′?γ″=0.015±0.002cm-1 with γ″≈0.010cm-1) for N′?10. An interpretation of this difference gives an order of magnitude for the perturbation parameters of the state A2Πu(v′=10)(ξ≈9cm-1, η≈0.06cm-1). The effect of this perturbation on the line intensities is negligible for N′?30.  相似文献   

7.
The intensities of the laser-induced fluorescence spectra of 130Te2, excited by Ar+ and He-Cd+ lasers, are measured for the AOu+-XOg+ and BOu+-XOg+ systems. The RKR potentials of the A, B and X states are calculated. These potentials are used for calculating Franck-Condon factors and r-centroids with due respect to rotation. The relative r-centroid dependences of the electronic transition strength were obtained first and then normalized in lifetimes.  相似文献   

8.
Multireference configuration interaction (MRD-CI) calculations are used to compute the electronic spectrum of glyoxal (CHO)2, a key species in atmospheric chemistry. The calculations place the first dipole-allowed transition 11Au←X1Ag at 2.80?eV (442.8?nm) with an oscillator strength of 0.0002 and the dipole forbidden 11Bg?←?X1Ag transition at 4.22?eV (293.8?nm), in accordance with prior experiments. In addition, a much stronger transition (31Bu?←?X1Ag) at 8.51?eV (145.7?nm) is predicted, which has not yet been reported in the literature. This transition corresponds to 1bg?→?2au excitation and can be characterized as π(CO)?→?π?(CO) type in accordance with the computed relatively large oscillator strength f?=?0.38. The corresponding triplet states are also computed.  相似文献   

9.
The vibronic coupling between the first excited S1 (21Ag) and the second excited S2 (11Bu) singlet electronic states in spectroscopy of trans‐1,3,5‐hexatriene molecule is investigated on the basis of a model consisting of two electronic states coupled by two vibrational modes. Employing a perturbation theory that treats the intramolecular couplings in a perturbative manner, the absorption and resonance Raman cross sections and excitation profiles of this molecule are calculated using the time‐correlation function formalism. The non‐Condon corrections are included in evaluation of cross sections. The multidimensional time‐domain integrals that arise in these calculations have been evaluated for the case in which S0 (11Ag) S2 (11Bu) electronic transition takes place between displaced and distorted harmonic potential energy surfaces. The calculated spectra are in good agreement with the experimental ones. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

10.
The infrared spectrum of the nitrogen molecule, excited in a microwave discharge, has been recorded in high resolution by Fourier spectrometry in the range 2500–15 000 cm?1. The precision of the measurements is estimated to be about 0.003 cm?1. We have analyzed 19 bands of the W3Δu-B3Πg system of 14N2, with 0 ≤ v′ ≤ 7, and three bands of 15N2 lying between 2500 and 5900 cm?1. The molecular constants of the 3Δu and B3Πg states have been determined by direct approach using an iterative nonlinear least-squares procedure. It has proved convenient to describe the levels of W3Δu state in a case a basis although in fact they approximate those of Hund's case b. Derived values of equilibrium constants of W3Δu are, in cm?1: Te = 8875.3347 (with origin taken in A, 3Σu+v = 0 level); ωe = 1506.4859; ωeχe = 12.5469; Be = 1.4702537; αB = 0.0170389; De = 0.55958 × 10?5. RKR potential energy curves for the two states are constructed, and the Franck-Condon factors calculated for the W-B system.  相似文献   

11.
The electronic structure of the title compound (1) has been investigated using He(Iα) PE spectroscopy and assuming the validity of Koopmans' theorem. It is found that: (a) in analogy to the situation prevailing in the cyclophanes, hyperconjugation of the out-of-phase linear combination of the π-orbitals with the ethano-bridge σ orbitals is symmetry-forbidden; (b) in agreement with the ideas developed in Part I of this series [1], the strong local B1u-type bending of the ethylene moieties does not affect their basis energy significantly; and (c) the “through-space” coupling of the two double-bond π orbitals is of the same order as the benzene π-orbital coupling in [2n] cyclophanes, even if the net contribution to the repulsion of the two double bonds is probably small. Because of the near degeneracy of the HOMO and HOMO — 1 of 1, the ground state of the radical cation 1+ cannot be determined uniquely: it is either2Ag or2B1u.  相似文献   

12.
The potential energy curves (PECs) are calculated for the 20 Λ-S states (X2Πg, A2Πu, B2Σ?g, a4Πu, b4Σ?g, b′4Πg, c4Σ?u, 12Σ+g, 12Σ+u, 12Σ?u, 14Σ+g, 14Σ+u, 14Δg, 14Δu, 16Σ+g, 16Σ+u, 16Πg, 16Πu, 24Πg and 24Πu) of O2+ cation and their corresponding 58 Ω states. Of these 20 Λ-S states, the 16Πu state is found to be repulsive. The 12Σ+g, 14Σ+u, c4Σ?u and 14Δu states are found to possess the double well. The b4Σ?g, 16Σ+g, 14Σ+u, a4Πu, A2Πu, 16Πg and 24Πg states are found to be inverted with the spin–orbit coupling effect included. The b′4Πg, 16Πg, 16Σ+g, 14Σ+u and 14Δu states, and the second well of the 12Σ+g state are found to be the weakly bound states. The b′4Πg state is found to possess one well with one barrier. The PECs are calculated by the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with the Davidson correction in combination with the aug-cc-pV6Z basis set. The core–valence correlation and scalar relativistic corrections are included. The convergent behaviour of present calculations is discussed with respect to the basis set and theoretical level. The spin–orbit coupling effect is accounted for. The PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated, and compared with available measurements. It demonstrates that the spectroscopic parameters reported here can be expected to be reliably predicted ones.  相似文献   

13.
Electron energy-loss spectra for the butadiene molecule were measured in the scattering angular range of 2.0° to 8.0°, in an energy-loss range from 2 to 50 eV, using 1000 eV incident electrons. The absolute generalized oscillator strength (GOS) and inelastic cross section have been determined for the \hbox{$\tilde{\rm X}^{1}$}?X1A g  → 11B u transition. The absolute elastic differential cross section was also determined spanning an angular range from 2.0° to 40.0°. From a small angle electron energy-loss spectrum, the optical oscillator distribution (photoabsorption spectrum) for the butadiene molecule was obtained in the 2 to 100 eV photon energy range. Accurate ab initio calculations have been performed, within the First Born Approximation, for generalized oscillator strength (GOS) and excitation energies for the \hbox{$\tilde{\rm X}^{1}$}?X1A g  → 11B u and \hbox{$\tilde{\rm X}^{1}$}?X1A g  → 21A g transitions. Our results emphasize the importance of using highly correlated wavefunctions and accurate methodologies in the calculation of the GOS for electron impact-induced electronic transitions in molecules.  相似文献   

14.
The emission spectra caused by the transitions from the ion-pair states and f0 g + and G1g of the I2 molecule are obtained by excitation of individual rovibronic levels of the molecule by the method of optical-optical double resonance. The emission spectra from the state F0 u + populated due to collisions I2(f) + I2(X) are also measured. By modeling the experimental emission spectra, the dipole moment functions for the electronic transitions f g + -B0 u + , A0 u + , and B″0 u + ; G1g-A0 u + and B″0 u + ; and F0 u + -X0 g + and a′0 g + of the iodine molecule are reconstructed.  相似文献   

15.
Analysis of the absorption spectrum of O2 in the Schumann-Runge bands (B3Σu?-X3Σg?) from the 2-0 to the 13-0 band yields oscillator strengths which are in good agreement with past theoretical calculations. Predissociation linewidths deduced from the data tend to be larger than theoretical predictions for v′ ≤ 5 and are reasonably near theory for v′ > 5. The qualitative dependence of the linewidths on vibrational level is in accord with that expected for a repulsive potential intersecting the B3Σ state near v′ = 4. For a given band the predissociation linewidth deduced from the spectra tends to increase as the total angular momentum increases. The new linewidths are smaller than some past experimental results, and this will have an impact on future calculations of the photodissociation rates of O2, NO, and H2O in the earth's upper atmosphere.  相似文献   

16.
用能量自洽法研究碱金属双原子分子的势能曲线   总被引:6,自引:1,他引:5       下载免费PDF全文
文静  孙卫国  冯灏 《物理学报》2000,49(12):2352-2356
用能量自洽法(ECM)研究了碱金属双原子分子一些电子激发态的势能曲线:Na2 分子的21Πg,43Πg和b3Π< sub>u电子激发态,K2分子的a3Σu,21Πg,B1Πu和A关键词: 能量自洽 双原子分子 势能 碱金属  相似文献   

17.
Existing high-resolution data for the O2+A2Πu - X2Πg Second Negative band system have been analyzed using a nonlinear least-squares fit that employs numerically diagonalized Hamiltonians. Values for the full set of molecular constants of the A2Πu and X2Πg states are obtained for the first time. In addition to values for ν0(v′, v″), Bv, and Dv, the values for the spin-orbit coupling constants Av are determined for both states. For the X2Πg state, which is near Hund's case (a), the agreement between these Av values and those predicted by theory is good. However, for the A2Πu state, which is much nearer to case (b), these Av values and theory disagree both in magnitude and in variation with vibrational level. The A2Πu state is an inverted state for vibrational levels v′ ≤ 5 and is a regular state for levels v′ = 6–8 (the upper limit of present high-resolution data). Λ-doubling parameters are determined for the X2Πg state, the only state where Λ-doubling is statistically significant. Spin-rotation interaction is not statistically significant for either state. Dunham Yi0 and Yi1 expansion coefficients are determined for each state. Theoretical Dv values calculated from RKR potentials are used to improve the Bv values in the reduction of the data.  相似文献   

18.
In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N2(C3Πu → B3 Πg, 0-2) and the first negative bands of N2 + (B2 Σu + → X2 Σg +, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH?(A 2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH(A2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N2(C3Πu → B3Πg, 0-0, 337.1 nm) and OH (A2Σ → X2Π, 0-0) are more greater than that on the emission intensity of N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm).  相似文献   

19.
The symmetry and energies of all optically active phonon modes in black phosphorous are determined by polarized Raman scattering and infrared reflection spectroscopy at room temperature. The obtained energies are; 365 and 470 cm-1 for Ag modes, 197 for Blg, 442 for B2g, 223 and 440 for B3g, 136 (TO) and 138 (LO) for Blu, and 468 (TO) and 470 (LO) for B2u, respectively. The small TO-LO splitting is related to the charge transfer between phosphorus atoms induced by the atomic displacement.  相似文献   

20.
The emission spectrum of the B3Πg-A3Σu+ system of the 15N2 molecule was recorded between 3500 and 12 500 cm−1 with a high-resolution Fourier spectrometer. Twelve bands with 0 < v′ < 5 and 0 < v″ < 9 are analyzed. The molecular parameters of the B3Πg and A3Σu+ states are obtained by a complete fitting procedure. Derived values of equilibrium constants are deduced; the Franck-Condon factors are calculated for the B-A system of 15N2.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号