Scattering Resonance State of Br＋HBr（v=0）→BrH（v＇=0）＋Br Reaction Explored by Partial Potential Energy Surface Method

The partial potential energy surface（PPES） of Br＋HBr（v=0）→BrH（v＇=0）＋Br was designed by coupling the vibration energy and the minimum energy of the corresponding reaction path, Vmep. All the calculations were performed at the theoritical level of QCISD（T）/6-311＋＋G＊＊//MP2/6-31 1＋＋G＊＊. Based on the analysis of PPES, the dynamic ＂Eyring Lake＂ mechanism gave birth to the scattering resonance state. The resonance energy was also obtained via PPES. Then a lifetime matrix of the resonance state was established by solving the translational wave-function via the numerical propagation method. Then the reaction resonance lifetime was calculated to be 125 fs. It is in good agreement with the experimental result.     

Theoretical Studies on Formation Mechanism of Resonance States for Na＋I2→Na^＋ ＋I2^－ System

An extended linear combination of arrangement channels-scattering wave-function(LCAC-SW) quantum scattering dynamic method combined with ab initio quantum chemical calculation was used to study the forma-tion mechanism of the resonance states for the collinear Na I2→Na^ I2^- I^2- ion-pair formation process on At-en-Lanting-Los potential energy surface. The resonance energy and the resonance width or the lifetime for the first resonance peak were calculated. The resonance can be identified as the Feshbach type and the physi-cal interpretation is given. The geometric structure of the resonance state for the title system has been opti-mized.     

Scattering Resonance States and Partial Potential Energy Surface of Reaction I+HI(v=0)→IH(v′=0) +I

Introduction Scattering resonance states in chemical reactionsattract much interest of both theorists and experimental-ists because the rate of a chemical reaction, state distri-bution and space distribution of the products are con-trolled by those states[1]. Scattering resonance states,also called quasi-bound states, are formed in theprocesses of energy transitions, such as collision andray radiation processes. Those states are very closelyrelated to the structure and spectroscopy of the tran…     

Quasi-Classical Trajectory Study of the Chemical Reaction Ca+CH3I

The Ca＋CH3I→CaI＋CH3 reaction system has been studied with the quasi-classical trajectory method on the extended Lond-Eyring-Polanyi-Sato（LEPS） potential energy surface. At collision energy Ecol=10.78 kJ/mol, the calculated results show that the CaI vibrational population peaks are located at v=2. The calculated cross section decreases slowly with the collision energy increasing. The angle product distributions tend toward backward scattering. The calculated （P2（J^1·K）） values deviate slightly from-0.5 and decrease with increasing collision energy. The Quasiclassical trajectory calculation（QCT） results are in reasonable agreement with experimental data. Moreover, the dynamics of the reaction has been discussed.     

Quasi-classical Trajectory Study of the Intramolecular Isotope Effect in the Reaction O（3p）＋H2/HD

Theoretical studies of the dynamics of the reactions O（3p）＋H2/HD（ν=0, j=0）→OH＋H have been performed with quasi-classical trajectory method （QCT） on an ab initio potential surface for the lowest triplet electronic state of H2O（aA＂）. The QCT-calculated integral cross sections are in good agreement with the earlier time-dependent quantum mechanics results. The state-resolved rotational distributions reveal that the product OH rotational distributions for O＋HD have a preference for populating highly internally excited states compared with the O＋H2 reaction. Distributions of differential cross sections show that directions of scattering are strongly dependent on the choice of quantum state. The polarization dependent generalized differential cross-sections and the distributions were calculated and a pronounced isotopic effect is revealed. The calculated results indicate that the product polarization is very sensitive to the mass factor.     

An Ab initio Theoretical Study on the Nonadiabatic Coupling for Na＋I2 Collision System

The ionic and neutral state potential energy surfaces (PESs) of Na I2 collision system have been calculated on QCISD(T) level by using ab initio method.The location and depth of the potential well,the collision radius and their fine structures have been analyzed at the equilibrium geometry of I2 molecule.The electronic transfer probabilities are also calculated in terms of Landau-Zener model.The lifetime of scattering resonance state is evaluated by the uncertainty principle.All the results have been compared with those obtained according to the Aten-Lanting-Los PES and Feng‘s PES.     

CO product distribution in the unimolecular dissociation of HCO

The unimolecular dissociation of HCO ground state was investigated with the time-dependent full-quantum symplectic propagation based on the newest potential energy surface of the system. Calculated energy and widths of HCO resonance states agree well with those in the literature. CO product distribution was systematically investigated. A simple model was presented to interpret the rovibrational distributions in HCO dissociation.     

Theoretical Studies on Reaction Mechanism of CH3SO with NO

The potential energy surface （PES） of CH3SO radical with NO reaction has been studied at MP2/6-311G（2df, p） and QCISD/6-311G（2df, p） levels. Geometries of the reactants, transition states （TS） and products were optimized at B3LYP/6-311G （d,p） level. The geometries of the transition states were found for the first time. The calculated results show that the reaction can proceed via singlet-state or triplet-state PES. Because of the high energy barrier of triplet surface, the singlet surface reactions are dominant. The topological analysis of electron density shows that there are two kinds of structaral transition states （the bifurcation-type ring structure transition state and the T-shaped conflict structure transition state） in the titled reaction. The total electronic density of the reactants, TS and products and the spin electronic density on the triplet surface were also discussed in this paper.     

THE THEORETICAL STUDY OF THE TRANSITION STATE OF THE REACTION H_2C=N=N—■H_2 AND ITS REACTION PATH

By means of energy gradient, the optimized geometries of diazomethane, diazirine and the transitionstate of the unimolecular reaction are discussed on the ground potential energy surface calculated byMINDO/3 SCF method. The nine vibrational normal modes in the transition state and the reaction pathcalculated with Fukui's IRC equation are also studied. The symmetry of the C_s point group of thereaction system is conserved throughout the reaction path. The MO correlation diagram shows that thisunimolecular reaction is symmetry admitted.     

Theoretical Study on Dehydrogenation Reactions of Silanol

The pathway of dehydrogenation reaction of silanol SiH3OH is investigated by ab initio Mo calculations using RHF/-31G basis set. The geometries of reactant, transition states and products are optimized on the singlet potential energy surface of the ground state. The activation energies, reaction heats, statistical A factor and activation entropies are calculated. The vibrational analysis of the reactant and the transition states is made. The reaction crgodography along the intrinsic reaction coordinate (IRC) are performed to examine the reaction mechanism.     

Scattering Resonance States and Partial Potential Energy Surface of Reaction I+HI(v=0)→IH(v′=0)+I

The partial potential energy surface of the I HI→IH I reaction involving the translational and vibrational motions has been constructed at the QCISD(T)//MP4SDQ level with the pseudo potential method that is helpful to interpreting the scattering resonance states. The lifetimes of the scattering resonance states in the title reaction obtained from the partial potential energy surface are about 90-120 fs, which agrees with the result of high-resolved threshold photodetachment spectroscopy of anion IHI- measured by Neumark.     

一种计算Feshbach共振态寿命的新方法

在自然碰撞坐标下构建偏分势能面, 利用数值传播方法求解沿反应坐标的核运动方程, 然后用过渡态波函数的相移因子构造反应体系共振态寿命矩阵. 这是一种直接计算化学反应散射共振寿命的量子散射方法. 用此方法计算了I+HI(υ)→IH(υ’)+I体系的第一散射共振态寿命, 所得数值与Neumark 的高分辨阈值光分离光谱实验的结果相一致.     

On the origin of the forward peak and backward oscillations in the F + H(2)(v = 0) --> HF(v' = 2) + H reaction

We present a semiclassical complex angular momentum (CAM) analysis of the forward scattering peak which occurs at a translational collision energy around 32 meV in the quantum mechanical calculations for the F + H(2)(v = 0, j = 0) --> HF(v' = 2, j' = 0) + H reaction on the Stark-Werner potential energy surface. The semiclassical CAM theory is modified to cover the forward and backward scattering angles. The peak is shown to result from constructive/destructive interference of the two Regge states associated with two resonances, one in the transition state region and the other in the exit channel van der Waals well. In addition, we demonstrate that the oscillations in the energy dependence of the backward differential cross section are caused by the interference between the direct backward scattering and the decay of the two resonance complexes returning to the backward direction after one full rotation.     

Energy resonance and inverse population of the product vibrational states for the reaction F + H2(v = 0) → HF(v′) + H,LCAC‐SW theoretical quantum scattering study

LCAC‐SW (linear combination of arrangement channel‐scattering wavefunction) method was used to calculate collinear state‐to‐state reaction probabilities for the reaction F + H₂(v = 0) → HF(v′) + H on the 6SEC potential energy surface. The results show that reaction probabilities P₀₂ and P₀₃ [i. e., v′ = 2,3 for reaction F + H₂ (v = 0) + HF(v′) + H] are primary, the population of product vibrational states is inverse and the reaction probabilities are oscillatory with collision energies, i.e., there is energy resonance in this reaction, which agrees with a new experiment.     

A time-dependent wave packet quantum scattering study of the reaction HD+ (v = 0 - 3;j0 = 1) + He --> HeH+(HeD+) + D(H)

Time-dependent wave packet quantum scattering (TWQS) calculations are presented for HD(+) (v = 0 - 3;j(0)=1) + He collisions in the center-of-mass collision energy (E(T)) range of 0.0-2.0 eV. The present TWQS approach accounts for Coriolis coupling and uses the ab initio potential energy surface of Palmieri et al. [Mol. Phys. 98, 1839 (2000)]. For a fixed total angular momentum J, the energy dependence of reaction probabilities exhibits quantum resonance structure. The resonances are more pronounced for low J values and for the HeH(+) + D channel than for the HeD(+) + H channel and are particularly prominent near threshold. The quantum effects are no longer discernable in the integral cross sections, which compare closely to quasiclassical trajectory calculations conducted on the same potential energy surface. The integral cross sections also compare well to recent state-selected experimental values over the same reactant and translational energy range. Classical impulsive dynamics and steric arguments can account for the significant isotope effect in favor of the deuteron transfer channel observed for HD(+)(v<3) and low translational energies. At higher reactant energies, angular momentum constraints favor the proton-transfer channel, and isotopic differences in the integral cross sections are no longer significant. The integral cross sections as well as the J dependence of partial cross sections exhibit a significant alignment effect in favor of collisions with the HD(+) rotational angular momentum vector perpendicular to the Jacobi R coordinate. This effect is most pronounced for the proton-transfer channel at low vibrational and translational energies.     

HO＋HoH→HoH＋oH反应的散射共振态与同位素效应的研究

在大气化学如燃烧反应和对流层各种有机化合物的降解中,HO＋HoH→HoH＋oH这一反应的研究格外受到关注．我们用abinitio方法构建了该体系的偏分势能面,并用其过渡区域里的动态Eyring湖解释散射共振态的形成机理,同时给出了共振能数据,估算了第一共振寿命．另外,我们还研究了同位素反应H^18O＋HOH→H^18OH＋OH和DO＋HOH→DOH＋OH．鉴于上述两个反应能够影响到等温层水中同位素的成分,HO＋HOH→HOH＋OH反应模型的建立对于理解O原子同位素的抽提反应有着重要的意义．     

Theoretical study on the partial potential energy surface and formation mechanism of the reactive resonance state of HO + CH4 → H2O + CH3 system

In the course of an extensive investigation aimed at understanding the detailed mechanism of a prototypical polyatomic reaction, several remarkable observations were uncovered. To interpret these findings, we surmise the existence of a reactive resonance in this polyatomic reaction. The concerned system is HO + CH₄ → H₂O + CH₃, of which the partial potential energy surface is constructed by the coupling between vibrational models and reactive coordinates. Then we explain the formation mechanism of the reactive resonance state by the partial potential energy surface. Finally, we estimated the lifetime of the resonance state, and it is about 45fs. The study of the reactive resonance in a polyatomic reaction is more than just an extension from a typical atom + diatom reaction. As shown here, it holds great promise to disentangle the elusive intramolecular vibrational dynamics of the transient collision complex in the critical transition‐state region. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

化学反应散射共振态的实验检测与理论模拟

化学反应中的散射共振态（或称反应性共振）控制着化学反应的分支比、产物的态分布及空间分布等。反应性共振的实验检测分为间接法和直接法。从理论上,一是构造反应体系的势能面,从势能面过渡态的结构来研究散射共振态;二是计算态-态反应动力学,尤其是用寿命矩阵来研究散射共振态。本文介绍反应性散射共振态的实验检测及理论模拟方法,并对今后的发展动向作出展望。