Quasiclassical trajectory calculations of the isotopic effect on cross-sections of reactions O(1D) + HCl (DCl,TCl)

The paper reports on a quasiclassical trajectory (QCT) study of the O(¹D) + HCl (DCl, TCl) reactions, with emphasis on the isotopic effect on cross-sections and branching ratio. The calculations were performed on the ground 1 ¹ A' potential energy surface (PES). The cross-sections and branching ratios of the O(¹D) + HCl (DCl, TCl) reaction have been calculated at the collision energies (E _col) of 3–15 kcal/mol. Obvious differences have been found in the energy dependences of the reaction cross-sections and branching ratios among these isotopic reactions.     

Quasiclassical calculation of the chemical reaction Ba+CH3I

This paper reports the quasiclassical trajectory (QCT) calculations on extended London–Eyring–Polanyi–Sato (LEPS) potential energy surface (PES) for the reaction of Ba atom with CH₃I. In the calculations, the Sato parameters needed in construction of the reaction PES are obtained from simulation of experimental results of BaI product vibrational distributions. The parameters obtained are further tested by comparison of the calculated BaI vibrational distributions with another research group's experimental results at different collision energy. In addition, the reaction cross-section versus collision energy, product BaI angular distribution and alignment are obtained by QCT calculations on the PES. The possible reaction configurations are also discussed upon the calculations.     

H-atom abstraction dynamics of reactions between Cl atoms and heterocyclic organic molecules

The HCl(v' = 0, J') rotational state distributions produced in the photoinitiated reactions of ground spin-orbit state Cl(2P3/2) atoms with the organic heterocycles oxirane (c-C2H4O), thiirane (c-C2H4S) and oxetane (c-C3H6O) have been measured using the technique of 2 + 1 resonance-enhanced multiphoton ionization in a time-of-flight mass spectrometer. In contrast to previous studies of H-atom abstraction dynamics by Cl atoms with linear functionalized molecules, the nascent HCl(v' = 0, J') products of the reactions of the three-membered heterocycles oxirane and thiirane are formed rotationally cold, with mean rotational energies <Erot> of (0.28 ± 0.02) kcal mol-1 and (0.31 ± 0.02) kcal mol-1, respectively. The reaction of Cl atoms with the four-membered heterocycle oxetane, however, results in more rotationally excited HCl(v' = 0, J') products for which <Erot> = (0.78 ± 0.03) kcal mol-1. Ab initio calculations were performed at the G2//MP2/6-311G(d,p) level to characterize molecular complexes and transition states on the reactive pathways. In all cases, the reactions were calculated to be barrierless, and weakly bound pre- and post-reaction complexes were located on the potential energy surfaces. The observed distributions and calculated reaction profiles are compared with previous studies of the reactions of Cl atoms with linear functionalized organic molecules and the consequences of the constrained molecular geometry on the HCl(v' = 0, J') rotational distribution discussed in terms of the dipole-dipole interaction model proposed previously.     

Investigation of isotope effects of dynamic properties for H(D) +OF reactions by the quasi-classical trajectory method

Quasi-classical trajectory (QCT) calculations are employed to study the dynamic properties for \mbox{H(D)} + \mbox{OF} reactions on the adiabatic potential energy surface (PES) of the \mbox{1}{ }^{3}\mbox{A}' triplet state. Obvious differences between the reaction probabilities for J = 0, integral cross sections for J \ne 0, branch ratios of the product and internuclear distances as well as product rotational alignments between the title reactions are found. These differences are attributed mainly to the different reduced masses of the reactants and the different zero-point energies (ZPEs) of the transition state.     

Experimental and quantum dynamical study on an asymmetric insertion reaction: state-to-state dynamics of O(1D) + HD(1Sigmag+, v' = 0, j' = 0)-->OH(Pi, v", N") + D(2S)

Quantum-state-resolved differential cross sections of the O((1)D) + HD --> OH + D reaction at the collision energy of 7.11 kJ/mol has been determined experimentally and theoretically. The results of the time-dependent wave-packet calculations are overall in good agreement with the crossed beam scattering data, providing a benchmark example of an asymmetric insertion reaction at the state-to-state scattering level. The good agreement between experiment and theory suggests that the underlying ground potential energy surface is generally correct and that the nonadiabatic effect involving the electronic excited pathway is apparently small in this system.     

Quasi-classical trajectory approach to the O（1D）＋HBr ）OH＋Br reaction stereo-dynamics on X1A＇ potential energy surface

The vector properties of reaction O(¹D)+HBr→ OH+Br on the potential energy surface (PES) of X¹A′ ground singlet state are studied by using the quasi-classical trajectory (QCT) theory. The polarization-dependent differential cross sections (PDDCSs), the average rotational alignment factor 2(j′· k)>, as well as the distributions reflecting vector correlations are also computed. The analysis of the results shows that the alignment and the orientation distribution of the rotation angular momentum vector of product molecule OH is influenced by both the effect of heavy-light-heavy (HLH) type mass combination and the deep well of PES.     

O(1D)+N2O→NO+NO反应的理论研究

应用三体模型及扩展的LEPS势能面(PES),对初始条件为(Ecol=55 kJ/mol,v=0,j=0)的O(1D)+N2O→NO+NO反应体系进行了准经典轨线(QCT)计算.根据计算结果对体系的势能面及反应机理进行详细的分析和讨论,较全面地研究了此反应体系的动力学特征.     

用准经典轨迹的理论方法研究H+ +H2反应

在新的势能面上,用准经典轨迹的方法对H H2反应体系进行了动力学研究．理论计算的结果发现,这个反应体系的前向和后向的角分布基本是对称的．同时还给出了在不同碰撞能下这个反应体系的转动态的分布情况．在碰撞能的从0．124到1．424 eV时,反应H H2的积分截面是随着碰撞能的增加而逐渐降低的．而且理论计算结果与实验结果也符合的非常好．     

Influence of ro-vibrational and isotope effects on the dynamics of the C(3 P)+ OD(X 2Π) → CO(X 1 Σ+) + D(2 S) reaction

The C(³ P)+OD(X ²Π) reaction has been studied by means of quantum mechanical real wave packet (RWP) and quasiclassical trajectory (QCT) methodologies on the ground potential energy surface of Zanchet et al. [J. Phys. Chem. A 110, 12017 (2006)]. Initial state selected total reaction probabilities at J?=?0 total angular momentum have been calculated for a wide range of collision energies. Product state-resolved integral cross-sections at selected collision energies and excitation functions have been determined from the RWP calculations using the J-shifting approximation and from QCT calculations. State-specific and thermal rate coefficients have been calculated using both methodologies up to 500 K. The effect of reagent rotational excitation on the dynamics for the C(³ P)+OH(X ²Π) and C(³ P)+OD(X ²Π) reactions has been investigated and interesting discrepancies between the QCT and RWP results have been found. The RWP results are found to be in an overall good agreement with the corresponding QCT results, although the QCT integral cross-section and rate coefficients are slightly smaller than those obtained from the RWP calculations.     

Vector correlations of the reaction O(1D) + H2 on the DK potential energy surface

This paper reports on the angular momentum polarization of the products of the reaction O(¹D₂) + H₂ via the quasiclassical trajectory (QCT) calculation on the DK (Dobbyn and Knowles) potential energy surface (PES). The four polarization-dependent differential cross-sections (PDDCS) (0, 0), (2, 0), (2, 2), (2, ?1) were calculated at different collision energies. The vector correlation between reagent velocity and product angular moment, the vector correlation between reagent, product velocity and product angular moment were studied. From the calculations, it can be obtained that the OH products are produced mainly in the plane of H–O–H plane. The changes of OH products angular momentum j ′ direction along with the increasing collision energies were ascribed to the existence of a new reaction mechanism.     

反应物的振动对碰撞反应(He, HD+)积分截面的影响

采用准经典轨线方法[1,2]计算了碰撞能范围为0.6～1.2电子伏时反应He+HD+ (v=1,j=0,1,2,3)→HeH++D和He+HD+ (v=1,j=0,1,2,3)→HeD++H的积分截面.通过跟有效的实验结果对比,发现计算结果略低于实验值,这可能是由于在计算中没有考虑量子效应而导致的.通过准经典轨线的计算结果与Tiwari等人的CS理论计算结果对比发现结果是基本相符合的,尤其是在几个碰撞能下几乎完全吻合.另外通过对比总结分析了V16以及V112势能面在不同的碰撞能以及不同的振转态下与CS理论计算的结果符合情况是的差异.同时重点分析了反应物的振转态对于反应的生成物以及积分截面的影响.     

蒜氨酸与牛及人血清白蛋白的相互作用

运用荧光光谱和同步荧光光谱法,研究在pH 7.40的Tris-HCI缓冲体系下,蒜氨酸与牛血清白蛋白(BSA)和人血清白蛋白(HSA)的相互作用。采用荧光分光光度计,以280 nm为激发波长,扫描300～500 nm范围的荧光发射光谱;分别设置波长差Δλ=15 nm和Δλ=60 nm扫描同步荧光光谱图;用Stem-Volmer和Lineweaver-Burk方程及热力学方程处理数据。荧光光谱法结果表明蒜氨酸能猝灭BSA及HAS的荧光;得到蒜氨酸与BSA反应的结合常数在298和310 K时分别9.81×102和6.15×102 L·mol-1;与HSA反应的结合常数在298和310 K时分别2.21×102和6.84×102 L·mol-1;蒜氨酸与两种蛋白的反应均为自发进行;与BSA的作用力为静电作用而与HSA的作用为疏水作用力;同步荧光光谱表明,蒜氨酸与BSA作用过程中主要影响酪氨酸残基,对HSA中的两种氨基酸残基均有影响。实验结果为研究蒜氨酸与生物小分子物质相互作用的机制提供了一定的理论依据。     

水分子高激发态的绝热势能面与光解机制

本文在从头算icMRCI+Q水平上,发展了水分子的基态和九个激发态?、?、B、C、D、D''、D''、?''和F的全维绝热势能面. 势能面的拟合采用了高斯过程回归并结合置换不变多项式方法. 通过选择大的活动空间与添加额外弥散函数的基组来准确描述这些里德堡状态,计算得到的垂直激发能和平衡构型与先前的理论与实验值十分吻合. 相对于前三个被广泛研究的低能量电子态,对高激发态光解的理论与实验研究仍然十分有限. 本文研究了水在真空紫外光解过程中涉及到的高激发态的全部三个解离通道. 特别是基于新发展的势能面,首次清晰地阐明了D-E''、E''-F、?-?和?-C电子态之间的锥形交叉等信息,文中详细讨论了这些电子激发态的非绝热解离途径,为阐明这些高里德堡态的光解离机制提供了帮助.     

低碰撞能下Li+HF(v=0－3，j=0－40)→LiF+H反应的立体动力学研究

基于2003年势能面,运用准经典轨线法(QCT)研究Li+HF→LiF+H反应立体动力学.探究较低碰撞能(1.15 kcal·mol-1-5.00 kcal·mol-1)下碰撞能、振转激发对极化微分反应截面(PDDCSs)和三矢量相关的P(θr,r)分布函数的影响,将积分散射截面与已有的理论及实验结果比较.结果显示,在较低碰撞能下碰撞能、振转激发对极化微分散射截面和三矢量相关的P(θr,r)分布函数有影响,但振转激发对极化微分反应截面和P(θr,r)分布的影响更大,碰撞能的增加使产物转动角动量后向散射的极化强度增大.在计算的能量范围内积分散射截面与其它的理论及实验结果符合较好.     

Stereodynamics of the O(3P) with H2 (D2) (v=0, j=0) reaction

Quasi-classical trajectory theory is used to study the reaction of O(³P) with H₂ (D₂) based on the ground ³A' potential energy surface (PES). The reaction cross section of the reaction O+H₂ → OH+H is in excellent agreement with the previous result. Vector correlations, product rotational alignment parameters 〈P₂ (j'·k)〉 and several polarized-dependent differential cross sections are further calculated for the reaction. The product polarization distribution exhibits different characteristics that can be ascribed to different motion paths on the PES, arising from various collision energies or mass factors.     

The Electronic and Infrared Absorption Spectra of Toluene-d

Abstract

The infrared and ultraviolet absorption spectra of toluene-d have been investigated for the first time in the regions 400 - 4000 cm^?1 and 2350 ?2750 A° respectively. The intense band at 2666.3 A°(37494 cm^?1) in the u.v. vapour absorption spectrum has been identified as the o,o band and others have been interpreted in terms of the three (519,632 and 785 cm^?1) ground state and the six (454,526,743,935,963 and 1180 cm^?1 excited state fundamentals. The correlation of the various frequencies of the ground and excited states of toluene and toluene-d has been done. The observed isotopic shift for toluene-d is 14 cm^?1.     

Theoretical study of the migration of the hydrogen atom adsorbed on aluminum nanowire

We study the behavior of a hydrogen atom adsorbed on aluminum nanowire based on density functional theory. In this study, we focus on the electronic structure, potential energy surface (PES), and quantum mechanical effects on hydrogen and deuterium atoms. The activation energy of the diffusion of a hydrogen atom to the axis direction is derived as 0.19 eV from PES calculations. The probability density, which is calculated by including quantum effects, is localized on an aluminum top site in both cases of hydrogen and deuterium atoms of the ground state. In addition, some excited states are distributed between aluminum atoms on the surface of the nanowire. The energy difference between the ground state and these excited states are below 0.1 eV, which is much smaller than the activation energy of PES calculations. Thus using these excited states, hydrogen and deuterium atoms may move to the axial direction easily. We also discuss the electronic structure of the nanowire surface using quantum energy density defined by one of the authors.     

Insertion and abstraction pathways in the reaction O(1D2) + H2-->OH+H

Rigorous quantum dynamical calculations have been performed on the ground 1 1A' and first excited 1 1A" electronic states of the title reaction, employing the most accurate potential energy surfaces available. Product rovibrational quantum state populations and rotational angular momentum alignment parameters are reported, and are compared with new experimental, and quasiclassical trajectory calculated results. The quantum calculations agree quantitatively with experiment, and reveal unequivocally that the 1 1A" excited state participates in the reaction.     

The reactions of Cl+ (3P) and Cl+ (1D) with hydrogen sulphide. A G2 molecular orbital study

G2 ab initio molecular orbital calculations have been performed to study the potential energy surfaces (PESs) associated with the reactions of Cl⁺ in its ³P ground state and in its ¹D first excited state with hydrogen sulphide. [H₂, Cl, S]⁺ singlet and triplet state cations present very different bonding characteristics. The latter are systematically ion-dipole or hydrogen-bonded weakly bound species, while the former are covalent molecular ions. As a consequence, although the Cl⁺(³P) is 34.5 kcal mol^?1 more stable than Cl⁺(¹D), the global minimum of the singlet PES lies 37.3 kcal mol^?1 below the global minimum of the triplet PES. Both singlet and triplet potential energy surfaces show significant differences with respect to those associated with Cl⁺ + H₂O reactions as well as with SH₂ reactions with F⁺. In both cases, the major product should be SH⁺ ₂; SH⁺ and HCl⁺ being the minor products, in agreement with the experimental evidence. The estimated heat of formation for the most stable H₂SCl⁺ singlet state species is 198 ± 1 kcal mol^?1.     

Exchange frequencies in the 2D Wigner crystal

Using path integral Monte Carlo we have calculated exchange frequencies as electrons undergo ring exchanges in a "clean" 2D Wigner crystal as a function of density. The results show agreement with WKB calculations at very low density, but show a more rapid increase with density near melting. Remarkably, the exchange Hamiltonian closely resembles the measured exchanges in 2D (3)He. Using the resulting multispin exchange model we find the spin Hamiltonian for r(s) < or = 175 +/- 10 is a frustrated antiferromagnetic; its likely ground state is a spin liquid. For lower density the ground state will be ferromagnetic.