Dynamics of the CH4+ O(~3 P) → CH_3(ν= 0) + OH(■= 0) reaction

The dynamics of the ground-state reaction of CH_4+ O(~3P) → CH_3(ν = 0) + OH( ν= 0) have attracted a great deal of attention both theoretically and experimentally. This rapid communication represents extensive quasi-classical trajectory calculations of the vibrational distributions on a unique full-dimensional ab initio potential energy surface for the title reaction, at the collision energy of relevance to previous crossed molecular beam experiments. The surface is constructed using the all electrons coupled-cluster singles and doubles approach plus quasi-perturbative triple excitations with optimized basis sets. A modified Shepard interpolation method is also employed for the construction. Good agreement between our calculations and the available experimental results has been achieved, opening the door for accurate dynamics on this surface.     

Quantum chemical study of the (Z)-2-penten-1-ol (HOCH2–CH = CHCH2CH3) + OH + O2 reactions

ABSTRACT

The mechanism and products of the reaction of (Z)-2-penten-1-ol [(Z)-PO21] with OH radical in the presence of O₂ have been elucidated by using high-level quantum chemical methods CCSD(T)/6-311+G(d,p)//BH&;HLYP/6-311++G(d,p). The calculations clearly indicate that addition channels contribute maximum to the total reaction and H-abstraction channels can be neglected at temperatures of 220–500 K. The rate constant for the reaction of OH radical with (Z)-PO21 at 298 K is computed to be 1.22 × 10^?10 cm³ molecule^?1 s^?1, which is in stronger agreement with the previously reported experimental values. The kinetic data obtained over the temperature range 220?500 K are used to derive an non-Arrhenius expression: k = 3.69 × 10^?13 × exp(1763.7/T) cm³ molecule^?1 s^?1. For the reaction of (Z)-PO21with OH radical in the presence of O₂, the major primary reaction products found in this study are propanal [CH₃CH₂C(O)H] and glycolaldehyde [HOCH₂C(O)H], whereas formaldehyde [HC(O)H], 2-hydroxybutanal [CH₃CH₂CH(OH)C(O)H] and the epoxide P18 are anticipated to be minor products. The calculated results are consistent with the recent experimental observations.     

CH3CH2+O(3P)反应机理的理论研究

利用abinitio方法对CH3CH2+O(3P)反应进行了理论研究,在MP2/6311+G(d,p)水平上优化得到了反应途径上的反应物、中间体、过渡态和产物的几何构型和谐振频率,并在QCISD(T)/6311+G(d,p)水平上进行单点能计算.计算结果表明:CH2O+CH3、CH3CHO+H和CH2CH2+OH是主要反应产物,其中CH2O+CH3主要来自反应通道A1:(R)→IM1→TS3→(A),CH3CHO+H主要来自反应通道B1:(R)→IM1→TS4→(B),CH2CH2+OH主要来自直接抽提反应通道C1和C2:(R)→TS1(TS2)→(C).计算结果同时表明该反应生成CO的通道能垒是非常高的,CO应该不是主要产物.     

甲醇分子(CH3OH)光谱性质的理论计算

研究了气相甲醇分子(CH3OH)基态和激发态性质。在对不同方法基组所得计算结果和实验结果进行比较之后,选用MP2(full)/6-311++G(2d,2p)理论方法进行计算,得到甲醇分子(CH3OH)基态和三重激发态的几何结构、能量以及频率信息;频率计算显示基态和三重态都为稳定构型。从三重态的结构出发,解释了三重态势能面为排斥型势能面的合理性。计算了甲醇分子单重激发态的垂直激发能,比较不同方法不同基组计算的甲醇分子单重激发态的垂直激发能,发现用TDDFT 中的b3p86方法使用6-311++G**基组的计算值和实验值符合得最好。计算得到的甲醇分子在MP2(full)/6-311++G(2d,2p)的绝热电离能和垂直电离能分别为11.18eV和11.32eV;计算得到的绝热电子亲和势与垂直电子亲和势分别为0.888eV和0.893eV。计算结果对实验研究有指导意义。     

甲醇分子(CH3OH)光谱性质的理论计算

研究了气相甲醇分子(CH3OH)基态和激发态性质。在对不同方法基组所得计算结果和实验结果进行比较之后,选用MP2(full)/6-311++G(2d,2p)理论方法进行计算,得到甲醇分子(CH3OH)基态和三重激发态的几何结构、能量以及频率信息;频率计算显示基态和三重态都为稳定构型。从三重态的结构出发,解释了三重态势能面为排斥型势能面的合理性。计算了甲醇分子单重激发态的垂直激发能,比较不同方法不同基组计算的甲醇分子单重激发态的垂直激发能,发现用TDDFT 中的b3p86方法使用6-311++G**基组的计算值和实验值符合得最好。计算得到的甲醇分子在MP2(full)/6-311++G(2d,2p)的绝热电离能和垂直电离能分别为11.18eV和11.32eV;计算得到的绝热电子亲和势与垂直电子亲和势分别为0.888eV和0.893eV。计算结果对实验研究有指导意义。     

CH3CH2+N(4S)反应机理的理论研究

利用abinitio方法对CH3CH2+N(4S)反应进行了理论研究,在MP2/6-311+G(d,p)水平上优化得到了反应途径上的反应物、中间体、过渡态和产物的几何构型和谐振频率,并在QCISD(T)/6-311+G(d,p)水平上进行单点能计算.计算结果表明,CH2CH2+3NH和H2CN+CH3是此反应主要产物,CH3CHN+H是此反应次要产物.产物CH2CH2+3NH主要来自直接氢抽提反应通道,H2CN+CH3来自加成-解离反应通道,CH3CHN+H来自加成-解离反应通道.     

CH(CH3)3 的耦合CH伸缩和弯曲振动的纠缠

以不同的多极量子数和初态,我们用约化的线性熵研究CH(CH3)3 的耦合CH伸缩和弯曲振动的动力学纠缠,结果表明：在多极量子数大于等于３时,态|0,2N>的最大纠缠能在较短的时间内得到;态|N,0>的纠缠振荡频率比态|0,2N>的要小,而振荡的幅度要大．     

Force and density study of the chemical reaction process OH2+H+→OH3 +

The force and density origin of the ionic reaction process OH₂+H⁺→OH₃ ⁺ is studied on the basis of the electrostatic force theory. In order to obtain reliable results, we have used the floating AO wavefunction (with minimal basis) which satisfies the Hellmann-Feynman theorem for the approaching proton. Accuracies of the results of the ordinary nuclear-centred AO wavefunction (with minimal basis plus polarization functions on hydrogen atoms) have been also examined. It is shown that the predominant origin of the driving force is the atomic dipole force which is caused by the transfer of the lone-pair density of OH₂ into the atomic region of H⁺ and the succeeding inward polarization of the transferred electron density. The exchange force due to density accumulation in the forming O-H⁺ bond region is of secondary importance. This is in contrast with the previous results for the radical reaction processes. The present reaction may be regarded as the transformation of the lone pair into the bond pair.     

Total cross sections of electron scattering by molecules NF3, PF3, N(CH3)3, P(CH3)3, NH(CH3)2, PH(CH3)2, NH2CH3 and PH2CH3 at 30–5000 eV

Total cross sections of electron scattering by eight molecules NF₃, PF₃, N(CH₃)₃, P(CH₃)₃, NH(CH₃)₂, PH(CH₃)₂, NH₂CH₃ and PH₂CH₃, which have some structural similarities, are calculated at the Hartree-Fork level by the modified additivity rule approach [D.H. Shi, J.F. Sun, Z.L. Zhu, H. Ma, Y.F. Liu, Eur. Phys. J. D 45, 253 (2007); D.H. Shi, J.F. Sun, Y.F. Liu, Z.L. Zhu, X.D. Yang, Chin. Opt. Lett. 4, 192 (2006)]. The modified additivity rule approach takes into considerations that the contributions of the geometric shielding effect vary as the energy of incident electrons, the dimension of target molecule, the number of electrons in the molecule and the number of atoms constituting the molecule. The present investigations cover the impact energy range from 30 to 5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories. Excellent agreement is observed even at energies of several tens of eV. It shows that the modified additivity rule approach is applicable to carry out the total cross section calculations of electron scattering by these molecules at intermediate and high energies, in particular over the energy range above 80 eV or so. It proves that the microscopic molecular properties, such as the geometrical size of the target and the number of atoms constituting the molecule, are of crucial importance in the TCS calculations. The new results for PH(CH₃)₂ and PH₂CH₃ are also presented at energies from 30 to 5000 eV, although no experimental and theoretical data are available for comparison. In the present calculations, the atoms are still represented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption terms.     

The influence of vibrational relaxation on the operation of the 119 μm CH3OH laser

Measurements of the pressure dependence of the relaxation rate of vibrationally excited molecules in the 119 m CH₃OH laser have been correlated with the pressure and pump power dependence of the output power in the framework of a rate-equation model for which numerical and approximate analytical solutions have been obtained. Both diffusion and collisional de-excitation are important, and substantial deviations from thermal equilibrium populations are deduced, consistent with an operating pressure range which increases with pump power.     

O (3P) + H2 → OH+H反应的立体动力学研究

用BMS1势能面[Brandão 等, J.Chem.Phys. 121, 8861 (2004)],选取碰撞能为34.6kcal/mol,用准经典轨线方法研究了O ( ) + 反应的立体动力学性质。计算并讨论了k与j'的夹角的分布关系P ( )以及描述k-k'- j'三者关系的二面角分布。（k为反应物速度方向,k'为产物的速度方向,j'为产物的角动量方向） 的峰值在90°附近并且关于90°呈对称性分布,这表明产物角动量的方向与初速度的方向垂直。二面角分布P( )关于散射平面呈反对称性分布,这一结果表明产物的角动量具有强烈的极化效应。另外,我们还研究了振动激发对产物角动量的影响,结果表明产物的矢量性质对反应物的初始振动态非常敏感。     

激光烧蚀Al等离子体与甲醇团簇反应中(CH3OH)nCH3O-的形成

激光烧蚀一分子束(LA-MB)法是研究金属离子与分子团簇反应的有效方法.在气相条件下,用飞行时间质谱观测到激光烧蚀Al等离子体与脉冲分子束超声膨胀产生的甲醇团簇碰撞反应生成的(CH30H)nCH3O-(n=3～23)团簇负离子.实验发现,此序列的团簇负离子主要生成于烧蚀激光作用于脉冲分子束的后段,(CH3OH)3CH3O-离子强度始终远远大于其后的离子,并且这些离子随尺寸大小的分布变化平缓.结合量化计算,在133LYP/6-31G(d)水平上得到(CH3OH)nCH3O-(n=1～4)的可能几何构形,并推断(CH3OH)3CH3O-为-幻数结构.     

激光烧蚀Al等离子体与甲醇团簇反应中 (CH3OH)nCH3O－的形成

激光烧蚀-分子束(LA-MB) 法是研究金属离子与分子团簇反应的有效方法。在气相条件下,用飞行时间质谱观测到激光烧蚀Al等离子体与脉冲分子束超声膨胀产生的甲醇团簇碰撞反应生成的(CH3OH)nCH3O－(n=3~23)团簇负离子。实验发现,此序列的团簇负离子主要生成于烧蚀激光作用于脉冲分子束的后段,(CH3OH)3CH3O－离子强度始终远远大于其后的离子,并且这些离子随尺寸大小的分布变化平缓。结合量化计算,在B3LYP/6-31G(d)水平上得到(CH3OH)nCH3O－(n=1~4)的可能几何构形,并推断(CH3OH)3CH3O¯为一幻数结构。     

Theoretical prediction of the optimal conditions for observing the stereodynamical vector properties of the C(~3P) + OH(X~2Π) → CO(X~1 Σ~+) + H(~2S) reaction

The best optimal initial reactant state and collision energy for observing the stereodynamical vector properties of the title reaction in the ground electronic state X2A potential energy surface(PES) [Zanchet et al. 2006 J. Phys. Chem. A 110 12017] are theoretically predicted using the quasi-classical trajectory(QCT) method for the first time. The calculated results reveal that the smallest value of the rotational quantum number j, larger vibrational quantum number v, and the lower strength of collision energy should be selected for offering the most obvious picture about the stereodynamical vector properties. Polarization-dependent differential cross sections and the angular momentum alignment distribution, P(θr) and P(Φr) in the center-of-mass frame, are obtained to gain an insight into the alignment and orientation of the product molecules. The rotational angular momentum vector j of CO is aligned to be perpendicular to reagent relative velocity k. The product polarizations align along the y axis, pointing to the positive direction of the y axis. A new method is developed to investigate massive reactions with various initial states and to further study the vector properties of the fundamental reactions in detail.     

Tris(hydroxymethyl)phosphine,P(CH2OH)3 – A convenient and effective new reagent for the fixation of protein samples for SEM imaging

Tris(hydroxymethyl)phosphine [P(CH₂OH)₃, THP] is demonstrated to be an alternative fixative to glutaraldehyde for preparation of proteinaceous specimens for SEM analysis. THP is easily prepared from commercially-available [P(CH₂OH)₄]Cl, and unlike many other alkylphosphines, is reasonably air-stable [>7 days at pH 7–8]. Experiments carried out with chicken breast muscle, cross-sectioned perpendicular to the muscle fibres and imaged using SEM, indicate that THP effectively fixes the muscle structure with minimal discolouration of the sample.     

LP-FTIR研究CH3C(O)CH=CH2与O3大气反应生成过氧化物的产率

在(298±2)K 温度和1.0×105 Pa(20% O2+80% N2)压力条件下,采用长光路傅里叶变换红外光谱(LP-FTIR)技术,实验室模拟研究甲基乙烯基酮(CH3C(O)CHCH2)与O3大气化学反应.从FTIR光谱中可以看出,产物中包括HCHO,HC(O)OH,CH3CHO和CH3C(O)CHO等羰基化合物,还有CO,CO2等.FTIR结合双通道过氧化物分析仪,测定了过氧化物的产率.其中,有机氢过氧化物(ROOH)为(10.7±0.4)% ,过氧化氢(H2O2)为(1.8±0.3)%.HPLC分析表明,ROOH主要为甲基过氧化氢(CH3OOH).可以认为,作为异戊二烯主要中间产物之一的甲基乙烯基酮与O3的反应是大气有机过氧化物的一个重要来源.至于反应过程中有机过氧化物的生成浓度呈现双峰的特征,其机制需作进一步的研究.     

Установка для получения изотоиа В10 методом обменной дистилляции комплекса (CH3)2O.BF3 1)

Zur Gewinnung der Neonisotope in gröβeren Mengen ist die Gegenstromdestillation bei 28 K die geeingnetste Methode. Um das Verfahren ökonomisch durchzuführen, wurden Verdampfer und Kondensator mit dem Neonkältekreislauf gekoppelt. Die Schüttung der KOlonne besteht aus V2A-Wendeln (1,6 mm × 1,8 mm × 0.2 mm) und hat eine Höhe von 6000 mm. Bei zweimaliger Destillation wurden folgende Konzenbtrationen eereicht: für ²²Ne 99,3% (maximal 99,5%), für ²⁰Ne 99,97–99,99%. ²⁴Ne wurde auf 1.2% (d. h. etwa das Vierfache der natürlichen Konzentration) angereichert.     

Stereodynamics in reaction O（1D） ＋ CH4 〉OH ＋ CH3

A theoretical study of the stereodynamics for reaction O(1D) + CH4→OH + CH3 has been carried out using the quasiclassical trajectory method(QCT) on a potential energy surface structured by Gonzalez et al. The integral cross sections(ICSs), differential cross sections(DCSs) and product rotational angular momentum polarization have been calculated. With the collision energy increasing, the ICS decreases. There is no threshold energy, because no barrier is found on the minimum energy path. The DCS results show that the backward and forward scatterings exist at the same time. With the collision energy increasing, the dominant rotation of the product changes from the right-handed direction to the left-handed direction in planes parallel to the scattering plane. In the isotopic effect study, the decrease of the mass factor weakens the polarization degree of the rotational angular momentum vectors of the products.