S(1D)+D2反应的立体动力学理论研究

在abinitio势能面上利用非含时量子反应散射理论研究了S(1D) D2反应在散射能为22.18kJ·mol-1时的立体动力学.计算的微分反应截面呈现弱反对称的前向后向散射,这一结果与以前的准经典结果和实验结果相一致.态分辨的极化依赖的微分反应截面和极化参数显示产物极化并非各向异性分布,这意味着在反应过程中由于势能面上存在一个深势阱从而形成了长寿命的复合物.     

转动激发对H＋LiF→HF＋Li的立体动力学影响的理论研究

用准经典轨线方法在Aguado-Paniagua2（AP2）势能面上计算了反应物转动量子态对H＋LiF→HF＋Li反应立体动力学的影响. 给出了关于产物和反应物之间矢量相关的P（μr）和P（ár）的分布情况. 同时计算了四个极化微分反应截面. 结果表明转动量子态对H＋LiF→HF＋Li反应的矢量性质有很大影响. 还计算了H＋LiF→HF＋Li反应的反应几率.     

反应物振动激发对反应He+H+2→HeH++H影响的准经典轨线研究

基于PPA势能面(Palmieri,P.;Puzzarini,C.;Aquilanti,V.Mol.Phys.,2000,98:1835),运用准经典轨线(quasi-classical trajectory)方法,对反应He+H+2(v=0-2,j=0)→HeH++H的立体动力学性质进行了理论研究.结果表明,反应物振动激发对反应的k-j'两矢量相关和k-k'-j'三矢量相关分布都产生了较大影响.除此之外,极化微分反应截面对振动量子数v也非常敏感.     

反应物振动激发对反应He+H+2→HeH++H影响的准经典轨线研究

基于PPA势能面(Palmieri, P.; Puzzarini, C.; Aquilanti, V. Mol. Phys., 2000, 98: 1835), 运用准经典轨线(quasi-classical trajectory)方法, 对反应He+H+2 (v=0-2, j=0)→HeH++H的立体动力学性质进行了理论研究. 结果表明, 反应物振动激发对反应的k-j'两矢量相关和k-k'-j'三矢量相关分布都产生了较大影响. 除此之外, 极化微分反应截面对振动量子数v也非常敏感.     

D+HCN反应的SVRT含时波包理论研究

基于Horst的势能面,用SVRT(SemirigidVibratingRotorTarget)方法对D+HCN反应进行了含时波包动力学研究,计算得到了不同初始振转态的总反应几率和积分反应截面,采用UniformJ-shifting方法得到该反应的热速率常数.计算结果与H+HCN反应进行了比和讨论.     

碰撞能对O(1D)+HBr→OH+Br反应的极化分布的影响

运用准经典轨线法结合Peterson从头计算势能面,在碰撞能分别为20.9,41.80和66.88 kJ/mol时,对放热反应O(1D)+HBr(v=0,j=0)→OH+Br(△H=-252.89 kJ/m01)进行了细致的立体动力学性质研究.反映k与j'两矢量相关的函数P(θr)的分布表明产物分子的转动角动量j'在垂直于反应物相对速度矢量k的方向上有强烈的取向分布,且随碰撞能的变化比较明显;反映k,k'与j'三矢量相关的函数P(φr)的分布表明产物转动角动量j'不仅有沿着y轴的取向效应,还有沿着y轴正向的弱定向效应,且这种弱定向效应随碰撞能的增加有所减弱;描述产物转动角动量j'的空间分布函数P(θr,φr)在(90°,90°)和(90°,270°)两处有两个明显的分布,随着碰撞能的增加,这两个集中分布越来越密集,碰撞能对该分布有一定的影响.产物分子的极化主要集中在垂直于散射面的平面内.除此之外,极化微分反应截面(PDDCSs)给出了反应产物的散射方向.     

振动激发对O+DCl→OD+Cl反应动力学性质的影响

采用准经典轨线方法讨论了反应物分子的振动激发对O+DCl→OD+Cl反应动力学性质的影响.计算结果表明,反应物分子的振动激发对(2π/σ)(dσ00/dωt),(2π/σ)(dσ20/dωt)和(2π/σ)(dσ22+/dωt)3个极化微分反应截面和产物分子转动角动量取向程度的影响比较显著.变化规律反映出反应物分子的高振动激发使产物分子倾向于在平行于散射面的平面内转动.     

反应物振动激发对反应He＋H2^2→HeH^＋＋H影响的准经典轨线研究

基于PPA势能面（Palmieri,P.;Puzzarini,C．;Aquilanti,V．Mol．Phys．,2000,98：1835）,运用准经典轨线（quasi—classical trajectory）方法,对反应He＋H2^＋（v=0—2,j=0）→HeH^＋＋H的立体动力学性质进行了理论研究．结果表明,反应物振动激发对反应的k-j’两矢量相关和k—k’-j’三矢量相关分布都产生了较大影响．除此之外,极化微分反应截面对振动量子数”也非常敏感．     

H+O_2(n_0,j_0)→HO+O及C+H_2(n_0,j_0)→CH+H体系选态反应截面的过渡态理论计算

本文用微正则过渡态理论计算了H+O_2(n_0,j_0)→HO+O和C+H_2(n_0,j_0)→CH+H在ab initio势能面上的选态反应截面σ_(n_0,j_0);E.分析了势能面性质对反应截面的影响。计算结果表明,在指定反应物分子的振动态n_0、转动态j_0时,两个反应体系的反应截面随相对平动能的增加先是增加后是减小(j_0=1,n_0=0除外);在给定相对平动能和反应物分子的转动态j_0时,随反应物分子的振动量子数n_0的增加,两个体系的选态反应截面均有较显著的增加,在指定相对平动能和反应物分子的振动态n_0时,H+O_2体系的选态反应截面随j_0的变化较为复杂,而C+H_2体系则比较简单(j_0=1除外).对于H+O_2反应体系,本文得到的反应截面与实验结果及准经典轨迹理论的计算结果符合得很好。     

H+O2(n0, j0)→HO+O及C+H2(n0, j0)→CH+H体系选态反应截面的过渡态理论计算

本文用微正则过渡态理论计算了H+O_2(n_0,j_0)→HO+O和C+H_2(n_0, j_0)→CH+H在ab initio势能面上的选态反应截面σ_(n_0,j_0); E.分析了势能面性质对反应截面的影响。计算结果表明, 在指定反应物分子的振动态n_0、转动态j_0时, 两个反应体系的反应截面随相对平动能的增加先是增加后是减小(j_0=1, n_0=0除外); 在给定相对平动能和反应物分子的转动态j_0时, 随反应物分子的振动量子数n_0的增加, 两个体系的选态反应截面均有较显著的增加, 在指定相对平动能和反应物分子的振动态n_0时, H+O_2体系的选态反应截面随j_0的变化较为复杂, 而C+H_2体系则比较简单(j_0=1除外)。对于H+O_2反应体系, 本文得到的反应截面与实验结果及准经典轨迹理论的计算结果符合得很好。     

The N2Ar potential energy surface

The potential energy surface for the N₂Ar system has been obtained assuming a spherical average interaction previously reported from this laboratory. The angular dependence has been assessed by a combined analysis of the integral and differential scattering cross sections and sonic spectroscope data. The potential energy surface is given via a parametric model. A similar potential energy surface for O₂Ar has been obtained with the same procedure. This surface is an improvement of an earlier one, because it reproduces the differential total cross sections recently measured.     

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.     

Quantum statistical and wave packet studies of insertion reactions of S(1D) with H2, HD, and D2

A thorough theoretical investigation of the reactions between S(1D) and various hydrogen isotopomers (H2, D2, and HD) has been carried out using a recent ab initio potential energy surface. State-resolved integral and differential cross sections, thermal rate constants, and their dependence on energy or temperature were obtained from quantum mechanical capture probabilities within a statistical model. For comparison, the J=0 reaction probabilities were also computed using an exact wave packet method. The statistical results are in excellent agreement with available exact differential and integral cross sections. The comparison with experimental results shows that the agreement is reasonably good in general, but some significant differences exist, particularly for the SD/SH branching ratio in the S(1D)+HD reaction.     

Study of the H+O2 reaction by means of quantum mechanical and statistical approaches: the dynamics on two different potential energy surfaces

The possible existence of a complex-forming pathway for the H+O(2) reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana et al., J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6 eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O(2)(v=0,j=1)-->OH(v(')=1,j('))+O process reasonably well.     

Simple semiclassical optical model of harpooning elementary proceses K + Br2

The ionic rearrangement, chemi-ionization, and dissociation processes in collisions K + Br₂ which proceed via the harpooning mechanism, are calculated in a classical trajectory approach using a semiclassical optical model for treating the electronic transition. For the transition matrix element in dependence on the nuclear configuration an approximate analytic expression, based on a one-electron model is derived, the ionic potential energy surface is represented by a semiempirical model function with polarization. Total and differential cross sections are obtained in qualitative agreement with molecular beam data. The results depend critically on potential and interaction parameters, inclusion of classically forbidden transitions is important. By an analysis of the product internal-state and translational-energy distributions the mechanism of the different processes is discussed.     

The Reaction X + Cl2→XCl + Cl (X = Mu,H, D). II. Comparison of experimental data with theoretical results derived from a new potential energy surface

We consider experimental implications for the Mu + Cl₂, H + Cl₂, and D + Cl₂ reactions of the extended London—Eyring—Polanyi—Sato (LEPS) potential energy surface derived from experimental data in paper I. In the present calculations, it is necessary to make additional implicit and explicit assumptions concerning the three-dimensional (3D) nature of the potential surface, since the inversion procedure of paper I yields information only on the collinear (1D) part of the surface. We have performed accurate 1D quantum calculations of reaction probabilities, which are then transformed into 3D by an information theoretic 1D → 3D transformation incorporating a constraint to allow for angular momentum transfer effects in light+heavy—heavy atom reactions. This procedure implicitly accounts for the 3D nature of the potential surface. The calculated vibrational and vibrotational product distributions are in good agreement with those determined in thermal chemiluminescence experiments. The Sato parameters for the 1D surface also define a full 3D surface. This is used as an approximation to the true surface, and its properties are explored in 3D quasiclassical trajectory calculations. Comparison is made for the H and D reactions with available chemiluminescence, molecular beam and kinetic experimental data for differential and total reaction cross sections, energy disposal, rate coefficients and Arrhenius parameters. Some kinetic isotope effects in the Mu, H, and D reactions are discussed using vibrationally adiabatic theory. Comparison is also made with results from other calculations in the literature for the H + Cl₂ and D + Cl₂ reactions.     

Model calculations of harpooning elementary processes in the system K + Br2

The dynamics of non-adiabatic elementary processes in the system K + Br₂ (exchange reaction, electron transfer, dissociation) are investigated using the quasiclassical trajectory method. Based on a estimation of the transition probability from the covalent to the ionic potential surface, the treatment is restricted to a calculation of the motion (1D, 2D, and 3D) on the ionic potential which is represented by a model function. Differential and total cross sections are determined, briefly discussed and compared with molecular-beam data.     

State-to-state reactive differential cross sections for the H+H2-->H2+H reaction on five different potential energy surfaces employing a new quantum wavepacket computer code: DIFFREALWAVE

State-to-state differential cross sections have been calculated for the hydrogen exchange reaction, H+H2-->H2+H, using five different high quality potential energy surfaces with the objective of examining the sensitivity of these detailed cross sections to the underlying potential energy surfaces. The calculations were performed using a new parallel computer code, DIFFREALWAVE. The code is based on the real wavepacket approach of Gray and Balint-Kurti [J. Chem. Phys. 108, 950 (1998)]. The calculations are parallelized over the helicity quantum number Omega' (i.e., the quantum number for the body-fixed z component of the total angular momentum) and wavepackets for each J,Omega' set are assigned to different processors, similar in spirit to the Coriolis-coupled processors approach of Goldfield and Gray [Comput. Phys. Commun. 84, 1 (1996)]. Calculations for J=0-24 have been performed to obtain converged state-to-state differential cross sections in the energy range from 0.4 to 1.2 eV. The calculations employ five different potential energy surfaces, the BKMP2 surface and a hierarchical family of four new ab initio surfaces [S. L. Mielke, et al., J. Chem. Phys. 116, 4142 (2002)]. This family of four surfaces has been calculated using three different hierarchical sets of basis functions and also an extrapolation to the complete basis set limit, the so called CCI surface. The CCI surface is the most accurate surface for the H3 system reported to date. Our calculations of differential cross sections are the first to be reported for the A2, A3, A4, and CCI surfaces. They show that there are some small differences in the cross sections obtained from the five different surfaces, particularly at higher energies. The calculations also show that the BKMP2 performs well and gives cross sections in very good agreement with the results from the CCI surface, displaying only small divergences at higher energies.