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1.
2.
Deperturbation analysis of the A(2)Π → X(2)Σ(+) and B(')(2)Σ(+) → X(2)Σ(+) emission spectra of (24)MgH is reported. Spectroscopic data for the v = 0 to 3 levels of the A (2)Π state and the v = 0 to 4 levels of the B'(2)Σ(+) state were fitted together using a single Hamiltonian matrix that includes (2)Π and (2)Σ(+) matrix elements, as well as off-diagonal elements coupling several vibrational levels of the two states. A Dunham-type fit was performed and the resulting Y(l,0) and Y(l,1) coefficients were used to generate Rydberg-Klein-Rees (RKR) potential curves for the A (2)Π and the B'(2)Σ(+) states. Vibrational overlap integrals were computed from the RKR potentials, and the off-diagonal matrix elements coupling the electronic wavefunctions (a(+) and b) were determined. Zero point dissociation energies (D(0)) of the A(2)Π and B'(2)Σ(+) states of (24)MgH were determined to be 12,957.5 ± 0.5 and 10,133.6 ± 0.5 cm(-1), respectively. Using the Y(0,1) coefficients, the equilibrium internuclear distances (r(e)) of the A(2)Π and B'(2)Σ(+) states were determined to be 1.67827(1) ? and 2.59404(4) A?, respectively. 相似文献
3.
《Chemical physics》1987,113(3):417-424
An ab initio unrestricted Hartree-Fock investigation on the C∞v (12Σ+, 12Π) and C2v (12A1, 12B1, 12B2) potential energy surfaces of the Si+ (2P) + H2 system is presented. In the study, the MIDI-1* minimal gaussian basis set of Huzinaga and co-workers is used. The analysis of the stationary points and main features of the potential energy surfaces involved and the comparison with those of the isovalent C+ (2P) + H2 → CH+ + H reaction reported in the literature have allowed us to understand the different dynamical behaviour exhibited by both isovalent systems near their respective threshold energies. 相似文献
4.
《Chemical physics letters》1985,115(1):29-33
Resonance Raman spectra of CS2 are presented at excitation wavelengths of 204 and 200 nm. Both spectra show activity in the symmetric (ν1) stretch and bending (ν2) modes consistent with a bent, symmetrically stretched 1B2(1Σu+) upper state. In addition, these spectra show activity of the transition involving two quanta in the asymmetric (ν3) stretch as well as progressions in ν1 and ν2 based upon this asymmetric mode overtone. 相似文献
5.
《Chemical physics letters》1986,123(4):315-320
In the paper, we compare the results of our ab initio calculations for the ro-vibrational branching ratios resulting from a (3+1) REMPI of H2 via the B1Σ+u state with the experimental data of Pratt, Poliakoff, Dehmer and Dehmer. These results indicate that non-Franck-Condon effects are less important here than in the (3+1) REMPI of H2 via the C1Πu state. We observe that the ΔJ = ±3 peaks in the photoelectron spectrum are of negligible strength and that the ratio of ΔJ = +1 to ΔJ = −1 peak is independent of the ionic vibrational state. A detailed analysis indicates that these features arise as a result of a dynamic interference between the do and dμ ionization channels and do not imply either the smallness of the d-wave or the smallness of the jt = 3 angular momentum coupling terms. 相似文献
6.
《Chemical physics》1987,115(3):423-432
The dissociation energy (De) for the O3(X̃ 1A1) → O2(X 3Σ−g) + O(3P) process is computed using MC SCF, CI, MBPT, and CCD methods. A full-valence MC SCF calculation utilizing a [9s5p3d1f/5s3p2d1f] basis set yields a De value of 0.43 eV, far below the experimental value of 1.13 eV, demonstrating the importance of correlation effects involving non-valence orbitals. A CI calculation in the same basis set allowing for all single and double excitations from three-reference configuration yields a De value of 0.72 eV. This value is increased to 1.06 eV when the Davidson correction is included. When the number of reference configurations is increased to eight, the resulting CI calculation gives a De value of 0.82 eV prior to the Davidson correction and 1.10 eV after this correction. 相似文献
7.
基于Sayós等构建的基态势能面, 运用准经典轨线方法对原子-分子反应K(2S)+HF(X1∑+)→KF(X1∑+)+ H(2S)的立体动力学性质进行了研究. 计算了该反应的极化微分反应截面、 两矢量k?j'相关分布函数P(θr)、 三矢量k?k'?j'相关分布函数P(?r)和空间分布函数P(θr,?r). 结果表明, 产物KF的转动角动量j′不仅在垂直于反应物相对速度矢量k的方向上有强烈的取向效应, 而且还定向于y轴的负方向, 转动角动量j′敏感地依赖于碰撞能. 相似文献
8.
《Chemical physics》1987,113(1):119-130
Rotational energy disposal has been measured in CN(X 2Σ, υ″ = 0, 1, 2) following 193 nm dissociation of HCN vapor at 295 K. The fractional populations for the three vibrational states are 0.56 ± 0.08, 0.33 ± 0.13, and 0.11 ± 0.03 for υ″ = 0, 1 and 2 respectively. This distribution is fit well by a Poisson distribution with an average vibrational quantum number of 0.55 corresponding to the average vibrational energy of 1128 ± 294 cm−1. This energy represents (10 ± 3)% of the available energy. The rotational distributions in all three vibrational states can be represented by a single surprisal which depends linearly on N″/N″max where N″max is the maximum value of the rotational quantum number permitted by energy conservation and the prior distribution is similarly constrained. The average energy in rotation is 1055 ± 373 cm−1 which represents (9 ± 3)% of that available for disposal. Time-dependence measurements indicate that product CN(X 2Σ, υ = 0) is formed in both a fast (τ < 80 ns) and a slow process. No evidence is found for the production of CN(A 2Π, υ ≈ 0). 相似文献
9.
《Chemical physics》1987,113(3):425-443
Total cross sections for production of HeH+ and H+ in the reaction of state-selected H+2 (v = 0 to 6) with He at 3.1 eV c.m. collision energy are measured by means of the threshold-photoelectron/photoion coincidence method, using pulsed synchrotron radiation. Both reaction cross sections are observed to rise with vibrational energy. The H+/HeH+ branching ratio, which is determined directly, remains approximately constant at about 0.3 for v ⩽ 3 and rises gradually for higher levels to reach the value 1.3 for v = 6. For v ⩽ 3 both reactions involve hard-type collisions and result in large-angle scattering. In contrast, at higher v levels, the HeH+ becomes essentially forward scattered with respect to the incident He direction, but with a velocity greater than that expected from the spectator stripping model. The H+ products are backward scattered with respect to the incident H+2 for v ⩽ 1 and receed faster from the He atom than the H products. This observation directly leads to the conclusion that collision-induced dissociation from v = 0 and 1 involves transitions to the first excited potential-energy surface. 相似文献
10.
《Chemical physics》1987,112(1):139-146
The electric dipole moment of the excited B1∑+ (υ′ = 0) state of MgO produced in a gas-phase reaction of Mg(1S) atoms and N2O is measured using the technique of Stark quantum-beat spectroscopy. It is shown to be |μυ′=0| = 5.94(24) D. The lifetime of the excited B1∑+ (υ′ = 0) state is determined as τ = 22.5(1.5) ns. Using laser excitation spectroscopy and by direct observation of the P(1) line splitting at high electric field strengths in the B1∑+−X1∑+ (0,0) system the ground state electric dipole moment is measured yielding |μυ=0| = 6.2(6) D. Furthermore an electric-field-induced Q branch is observed. 相似文献
11.
A crossed molecular beams, state-to-state scattering study was carried out on the F+H2→HF+H reaction at the collision energy of 5.02 kJ/mol, using the highly sensitive H atom Rydberg tagging time-of-flight method. All the peaks in the TOF spectra can be clearly assigned to the ro-vibrational structures of the HF product. The forward scattering of the HF product at v′=3 has been observed. The small forward scattering of the HF product at v′=2 has also been detected. Detailed theoretical analysis is required in order to fully understand the dynamical origin of these forward scattering products at this high collision energy. 相似文献
12.
A global three dimensional potential energy surface for the F+H2→HF+H reaction has been developed by spline interpolation of about 15,000 symmetry-unique ab initio points, obtained from the multi-reference configuration interaction level with Davidson correction using the aug-cc-pV5Z basis set. In the entrance channel the spin-orbit coupling energy is also included. 相似文献
13.
The rate coefficients for the capture process CH + H(2)→ CH(3) and the reactions CH + H(2)→ CH(2) + H (abstraction), CH + H(2) (exchange) have been calculated in the 200-800 K temperature range, using the quasiclassical trajectory (QCT) method and the most recent global potential energy surface. The reactions, which are of interest in combustion and in astrochemistry, proceed via the formation of long-lived CH(3) collision complexes, and the three H atoms become equivalent. QCT rate coefficients for capture are in quite good agreement with experiments. However, an important zero point energy (ZPE) leakage problem occurs in the QCT calculations for the abstraction, exchange and inelastic exit channels. To account for this issue, a pragmatic but accurate approach has been applied, leading to a good agreement with experimental abstraction rate coefficients. Exchange rate coefficients have also been calculated using this approach. Finally, calculations employing QCT capture/phase space theory (PST) models have been carried out, leading to similar values for the abstraction rate coefficients as the QCT and previous quantum mechanical capture/PST methods. This suggests that QCT capture/PST models are a good alternative to the QCT method for this and similar systems. 相似文献
14.
A new global potential energy surface is reported for the ground state ((4)A(")) of the reaction H((2)S) + NH(X(3)Σ(-)) → N((4)S) + H(2) from a set of accurate ab initio data, which were computed using the multi-reference configuration interaction with a basis set of aug-cc-pV5Z. The many-body expansion and neural network methods have been used to construct the new potential energy surface. The topographical features of the new global potential energy surface are presented. The predicted barrier height is lower than previous theoretical estimates and the heat of reaction with zero-point energy is closer to experimental results. The quantum reactive scattering dynamics calculation was carried out over a range of collision energies (0-1.0 eV) on the new potential energy surface. The reaction probabilities, integral cross-section, and rate constants for the title reaction were calculated. The calculated rate constants are in excellent agreement with the available experimental results. 相似文献
15.
Steric effect in the energy transfer reaction of N(2)(A(3)Σ(u)(+)) + NO(X(2)Π) → NO(A(2)Σ(+)) + N(2)(X(1)Σ(g)(+)) has been studied under crossed beam conditions at a collision energy of ~0.07 eV by using an aligned N(2)(A(3)Σ(u)(+)) beam prepared by a magnetic hexapole. The emission intensity of NO(A(2)Σ(+)) has been measured as a function of the magnetic orientation field direction (i.e., alignment of N(2)(A(3)Σ(u)(+))) in the collision frame. A significant alignment effect on the energy transfer probability is observed. The shape of the steric opacity function turns out to be most reactive at the oblique configuration of N(2)(A(3)Σ(u)(+)) with an orientation angle of γ(v(R)) ~ 45° with respect to the relative velocity vector (v(R)), which has a good correlation with the spatial distribution of the 2pπ(g)* molecular orbital of N(2)(A(3)Σ(u)(+)). We propose the electron exchange mechanism in which the energy transfer probability is dominantly controlled by the orbital overlap between N(2)(2pπ(g)*) and NO(6σ). 相似文献
16.
Ab initio potential energy surfaces and the corresponding analytical energy functions of the ground 1A' and excited 2A' states for the Li(2(2)P) plus H(2) reaction are constructed. Quasiclassical trajectory calculations on the fitted energy functions are performed to characterize the reactions of Li(2(2)P) with H(2)(v = 0, j = 1) and H(2)(v = 1, j = 1) as well as the reaction when the vibrational energy is replaced by collision energy. For simplicity, the transition probability is assumed to be unity when the trajectories go through the crossing seam region and change to the lower surface. The calculated rotational distributions of LiH(v = 0) for both H(2)(v = 0, j = 1) and H(2)(v = 1, j = 1) reactions are single-peaked with the maximum population at j' = 7, consistent with the previous observation. The vibrational excitation of H(2)(v = 1) may enhance the reaction cross section of LiH(v' = 0) by about 200 times, as compared to a result of 93-107 reported in the experimental measurements. In contrast, the enhancement is 3.1, if the same amount of energy is deposited in the translational states. This endothermic reaction can be considered as an analog of late barrier. According to the trajectory analysis, the vibrational excitation enlarges the H-H distance in the entrance channel to facilitate the reaction, but the excess energy may not open up additional reaction configuration. 相似文献
17.
A global potential energy surface (PES) for the ground electronic state of FH(2)O is constructed based on more than 30 000 ab initio points at the multi-reference configuration interaction level. The PES features a pre-reaction van der Waals well and two post-reaction hydrogen-bonded complexes, as well as a "reactant-like" transition state with a classical barrier of 3.8 kcal∕mol. The adiabatic F + H(2)O → HF + OH reaction dynamics on this PES was investigated using a standard quasi-classical trajectory method. In agreement with experiment, the HF product contains significant vibrational excitation with limited rotational excitation, while the OH product is internally cold, reflecting its spectator role in the reaction. The products are primarily scattered in the backward direction, consistent with a direct abstraction mechanism. 相似文献
18.
We present converged exact quantum wave packet calculations of reaction probabilities, integral cross sections, and thermal rate coefficients for the title reaction. Calculations have been carried out on the ground 1(2)A' global adiabatic potential energy surface of Deskevich et al. [J. Chem. Phys. 124, 224303 (2006)]. Converged wave packet reaction probabilities at selected values of the total angular momentum up to a partial wave of J = 140 with the HCl reagent initially selected in the v = 0, j = 0-16 rovibrational states have been obtained for the collision energy range from threshold up to 0.8 eV. The present calculations confirm an important enhancement of reactivity with rotational excitation of the HCl molecule. First, accurate integral cross sections and rate constants have been calculated and compared with the available experimental data. 相似文献
19.
《Chemical physics》1987,118(2):153-160
Collinear (two-mathematical-dimensional (2MD)) coupled-channel quantum-mechanical calculations have been performed on the reactions D + FH(ν = 0, 1, 2) → DF(ν′) + H and H + FD(ν = 0, 1, 2, 3) → HF(ν′) + D on a potential energy surface with a 40 kcal/mole barrier to exchange. This barrier height is close to that predicted by ab initio calculations and suggested by experiments. The relative effectiveness of reagent vibrational and translational excitation to promote reaction is considered. A one-mathematical-dimensional (1MD) model for these reactions is constructed and is shown to work very well for the D + FH reaction at high temperatures, and less well for that reaction at lower temperatures as well as for the reverse H + FD reaction. Possible reasons for the breakdowns of this model are discussed. 相似文献
20.
《Chemical physics》1986,101(2):291-298
The formation processes of N+2 (X 2Σ+g) resulting from the He(2 3S) + N2 Penning ionization and the thermal energy He+, He+2 + N2 charge transfer reaction are studied by observing the N+2 (B 2Σ+u ← X 2Σ+g) laser-induced fluorescence (LIF) in a flowing afterglow. In both reactions, the vibrational population) decrease monotonically with increasing vibrational quantum number from υ″ = 0 to 3, and a population inversion with a peak at υ″ = 4 is seen. In the He(2 3S) + N2 Penning ionization, the vibrational populations of N+2 (X, υ″ = 0–2) are explained by a direct channel and the B —X radiative cascade, while those of N+2 (X, υ″ = 4–6) are ascribed to the collision-induced electronic energy transfer between the A 2Πu and X 2Σ+g states. In the He+, He+2 + N2 reaction, the N+2 (X, υ″ = 0–3) is interpreted as the B−X radiative cascade and the collisional quenching of the unidentified states produced from the He+ + N2 reaction, while the collision-induced electronic energy transfer from the N+2 (A) state produced through the He+2 + N2 reaction is probably important for the formation of N+2 (X, υ″ = 4–6). 相似文献