Energy and rotation-dependent stereodynamics of H(~2S) + NH(a~1?) → H_2(X~1Σ_g~+) + N(~2D) reaction

Quasi-classical trajectory calculations are performed to study the stereodynamics of the H(~2S) + NH(a~1?) →H_2(X~1Σ_g~+) + N(~2D) reaction based on the first excited state NH_2(1~2A') potential energy surface reported by Li et al.[Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644] for the first time. We observe the changes of differential cross-sections at different collision energies and different initial reagent rotational excitations. The influence of collision energy on the k–k' distribution can be attributed to a purely impulsive effect. Initial reagent rotational excitation transforms the reaction mechanism from insertion to abstraction. The effect of initial reagent rotational excitations on k–k' distribution can be explained by the rotational excitation enlarging the rotational rate of reagent NH in the entrance channel to reduce the probability of collision between incidence H atom and H atom of target molecular. We also investigate the changes of vector correlations and find that the rotational angular momentum vector j' of the product H_2 is not only aligned, but also oriented along the y axis. The alignment parameter, the disposal of total angular momentum and the reaction mechanism are all analyzed carefully to explain the polarization behavior of the product rotational angular moment.     

Mechanism analysis of reaction S~+(~2D)+H_2(X~1Σ_g~+) → SH~+(X~3Σ~-) + H(~2S) based on the quantum state-to-state dynamics

We present a state-to-state dynamical calculation on the reaction S~++ H_2→ SH~+ +H based on an accurate ~X2 A~″ potential surface. Some reaction properties, such as reaction probability, integral cross sections, product distribution, etc.,are found to be those with characteristics of an indirect reaction. The oscillating structures appearing in reaction probability versus collision energy are considered to be the consequence of the deep potential well in the reaction. The comparison of the present total integral cross sections with the previous quasi-classical trajectory results shows that the quantum effect is more important at low collision energies. In addition, the quantum number inversion in the rotational distribution of the product is regarded as the result of the heavy–light–light mass combination, which is not effective for the vibrational excitation. For the collision energies considered, the product differential cross sections of the title reaction are mainly concentrated in the forward and backward regions, which suggests that there is a long-life intermediate complex in the reaction process.     

State-to-state quantum dynamics of the N(~4S)+H_2(X~1Σ~+) → NH(X~3Σ~-)+H(~2S) reaction and its reaction mechanism analysis

Quantum state-to-state dynamics of the N(4S) + H-2(X1+Σ) → NH(X3Σ) + H(2S) reaction is reported in an accurate novel potential energy surface constructed by Zhai et al.(2011 J. Chem. Phys. 135 104314). The time-dependent wave packet method, which is implemented on graphics processing units, is used to calculate the differential cross sections. The influences of the collision energy on the product state-resolved integral cross sections and total differential cross sections are calculated and discussed. It is found that the products NH are predominated by the backward scattering due to the small impact parameter collisions, with only minor components being forward and sideways scattered, and have an inverted rotational distribution and no inversion in vibrational distributions; both rebound and stripping mechanisms exist in the case of high collision energies.     

H_2(X~1∑_g~ )—H_2(E~1∑_g~ )系统的相互作用

采用显含电子对相关坐标的波函数,在微扰论的框架下计算了E~l∑_g~ 态氢分子与基态氢分子取cross构型时的中长程相互作用。结果表明,该相互作用在分子间距6.5α_0附近存在着一个活化能势垒,在4.5α_0附近显示出较强的化学键行为。     

State-to-state dynamics of F(~2P) + HO(~2Π) → O(~3P) + HF(~1Σ~+)reaction on 1~3A〞 potential energy surface

State-to-state time-dependent quantum dynamics calculations are carried out to study F(~2P) + HO(~2Π) → O(~3P) +HF(~1Σ~+) reaction on 1~3A〞 ground potential energy surface(PES). The vibrationally resolved reaction probabilities and the total integral cross section agree well with the previous results. Due to the heavy–light–heavy(HLH) system and the large exoergicity, the obvious vibrational inversion is found in a state-resolved integral cross section. The total differential cross section is found to be forward–backward scattering biased with strong oscillations at energy lower than a threshold of 0.10 eV, which is the indication of the indirect complex-forming mechanism. When the collision energy increases to greater than 0.10 eV, the angular distribution of the product becomes a strong forward scattering, and almost all the products are distributed at θ_t = 0°. This forward-peaked distribution can be attributed to the larger J partial waves and the property of the F atom itself, which make this reaction a direct abstraction process. The state-resolved differential cross sections are basically forward-backward symmetric for v' = 0, 1, and 2 at a collision energy of 0.07 eV; for a collision energy of 0.30 eV,it changes from backward/sideward scattering to forward peaked as v increasing from 0 to 3. These results indicate that the contribution of differential cross sections with more highly vibrational excited states to the total differential cross sections is principal, which further verifies the vibrational inversion in the products.     

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.     

Vibrational and rotational excitation effects of the N(2D) + D2(X1Σg +) → ND(X3Σ+) + D(2S) reaction

The effects of the rovibrational excitation of reactants in the N(²D) + D₂(X¹Σ_g⁺) → ND(X³Σ⁺) + D(²S) reaction are calculated in a collision energy range from the threshold to 1.0 eV using the time-dependent wave packet approach and a second-order split operator. The reaction probability, integral cross-section, differential cross-section and rate constant of the title reaction are calculated. The integral cross-section and rate constant of the initial states v = 0, j = 0, 1, are in good agreement with experimental data available in the literature. The rotational excitation of the D₂ molecule has little effect on reaction probability, integral cross-section and the rate constant, but it increased the sideways and forward scattering signals. The vibrational excitation of the D₂ molecule reduced the threshold and broke up the forward–backward symmetry of the differential cross-section; it also increased the forward scattering signals. This may be because the vibrational excitation of the D₂ molecule reduced the lifetime of the intermediate complex.     

HNCO在201 nm的离子成像光解动力学:CO(X~1Σ~+)与NH(a~1△)态相关性（英文）

本文通过时间切片离子速度成像技术在201 nm附近研究了HNCO分子在S_1电子激发态的光解动力学.CO产物通过共振增强多光子电离的方法进行了选态探测,获得了CO产物的振动基态和激发态切片影像.从CO的影像得到了解离产物的能量分布和空间角分布,确定了NH(a~1△)产物的振转态分布信息.研究发现~1NH的振动分支比(v=1/v=0)随CO(v=0)转动能的增大先增大后下降,展现了~1NH与CO之间特殊的态态相关性.大约一半的可资用能分配给解离产物的平动自由度.负的各向异性参数表明HNCO的光解是个快速的直接解离过程.     

Kinetics and dynamics of the S(1D2) + H2 → SH + H reaction at very low temperatures and collision energies

We report combined studies on the prototypical S(1D2) + H2 insertion reaction. Kinetics and crossed-beam experiments are performed in experimental conditions approaching the cold energy regime, yielding absolute rate coefficients down to 5.8 K and relative integral cross sections to collision energies as low as 0.68 meV. They are supported by quantum calculations on a potential energy surface treating long-range interactions accurately. All results are consistent and the excitation function behavior is explained in terms of the cumulative contribution of various partial waves.     

Ar气对~(39)K_2分子C~1Ⅱ_u→X~1∑_g~+LIF光谱的碰撞猝灭效应

实验测量了缓冲气体Ar气对~(39)K_2分子C~1Π_u(v′=O,J′=53)→X~1∑_g~+(v″=5,6,J″=52,54)LIF光谱的碰撞猝灭效应.用稳态碰撞模型推导出LIF光谱强度I对气体压强P=P_(Ar)+P_K的函数关系.用上述模型拟合出的I-P曲线和实验数据的符合,对拟合所得参数C_1的进一步分析指出:热管炉后向探测LIF光谱方法比非增益荧光探测法的灵敏度可提高2倍以上.     

Stereodynamics study of reactions N(~2D)+HD→NH+D and ND+H

The product polarizations of the title reactions are investigated by employing the quasi-classical trajectory (QCT) method. The four generalized polarization-dependent differential cross-sections (PDDCSs) $({2\pi } / \sigma )(\d\sigma _{00} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{20} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{22 + } / \d\omega _t )$, and $({2\pi } / \sigma )(\d\sigma _{21 - } / \d\omega _t )$ are calculated in the centre-of-mass frame. The distribution of the angle between ${{\bm k}}$ and ${{\bm j^\prime }}$, $P(\theta _r )$, the distribution of the dihedral angle denoting ${{\bm k}}${--}$\bm k^\prime $--$\bm j^\prime $ correlation, $P(\phi _r )$, as well as the angular distribution of product rotational vectors in the form of polar plots $P(\theta _r ,\phi _r )$ are calculated. The isotope effect is also revealed and primarily attributed to the difference in mass factor between the two title reactions.     

(C_5H_(11)N_2)~+和(C_7H_(12)N_2)~(2+)的NMR研究

结合1H NMR,13C NMR谱,分别对钨、钼配合物{WO2(C10H6O2)2(C5H11N2)2[H2N(CH2)3NH2]}3(1),{(C5H11N2)2[H2N(CH2)3NH2][MoO2(C10H6O2)2]}(2),{(C7H12N2)2[MoO2(C10H8O2)2]}(3)晶体结构中小分子环进行了归属.其中,配合物1和2中(C5H11N2)+的NMR研究证实了六元环由1,3-丙二胺和乙腈化合而成,配合物3中(C7H12N2)2+的NMR谱图证实了七元环由乙二胺和乙酰丙酮化合而成,并且推导出这些亲核加成-消除反应的反应机理.配合物1~3中的小分子环的合成在其它体系中尚未见报导,而在合成它们的反应中作为新产物随主体晶体析出,并由晶体结构解析和NMR得到了证实.     

The ion-molecule reaction O+ (4S) + N2(X1Σ+) → NO+ (X1Σ +, v′) + N(4S) and the predissociation of the A2Σ+ and B2Π states of N2O+

The potential energy surfaces (PESs) for several electronic states involved in the reaction O⁺ (⁴S) + N₂(X¹Σ⁺) → NO⁺ (X¹Σ ⁺, v′) + N(⁴S) and the role of the ionic N₂O⁺ intermediate have been investigated by ab initio calculations. The ⁴A″ PES, which correlates with the ground state educts, has a barrier of about 1 eV, and therefore at low collision energies the reaction cannot take place adiabatically on this surface. However, the spin-orbit coupling in the entrance channel allows the system to pass into the Renner-Teller system of the X² Π electronic ground state of the N₂O⁺ intermediate. The reaction then proceeds on these surfaces up to the region in the exit channel where a similar coupling allows it to reach the product quartet asymptote. At collision energies higher than about 1 eV, the reaction proceeds mainly on the adiabatic PES of the ⁴A″ state. The A²Σ⁺ state of N₂O⁺ predissociates via a vibronic coupling with the B²Π state, and in bent structures via a spin-orbit coupling with the ⁴A″ component of the ⁴II state. The electronic structure of the B²Π state is found to be of crucial importance for the understanding of the reactive processes in low lying electronic states of N₂O⁺.     

HBr(X~1Σ~+ν~″=5)分子与H_2,N_2,CO_2和HBr间的近共振振动-振动能量转移

利用简并受激超拉曼泵浦激发HBr(Χ~1Σ~+ν~″=5)振动态,由高分辨瞬时激光感应荧光(LIF)探测碰撞弛豫后HBr(ν~″≤5)各振动态时间分辨布居数的演化过程,得到了HBr(ν~″=5)分别与分子M(H_2,N_2,CO_2和HBr)的碰撞弛豫速率系数。对于M=CO_2,近共振的1-1振动-振动(V-V)能量转移是有效的,这一结果表明CO_2强的红外振动模对近共振V-V能量转移是有利的。而红外禁戒跃迁的N_2(0-1)的近共振V-V转移虽然也能观察到,但相应速率系数比CO_2小2个量级。碰撞分子的振动跃迁红外活性越强,能量转移速率系数越大。在HBr(ν~″=5)+HBr的自弛豫过程中,单量子弛豫率占总弛豫率的70%,而双量子弛豫约占25%。在HBr(ν~″=5)+H_2中,只有2-1的V-V近共振过程是重要的。同时还研究了V-V近共振能量转移速率系数与温度变化的关系,对于CO_2的1-1近共振,V-V能量转移速率系数随温度的增加而减小;对于H_2和HBr,其弛豫速率系数随温度的增加而增加;对于N_2,其弛豫速率系数随温度的增加而缓慢增加。     

异氰酸分子NH(a~1△)+CO(X~1∑~+)通道在193 nm的离子成像光解动力学研究（英文）

利用时间切片离子速度成像技术在193 nm研究了异氰酸分子(HNCO)的光解动力学.NH(α~1△)产物通过共振增强多光子电离的方法进行了探测.对NH(α~1△)产物的振动基态和激发态(v=0和1)进行了影像探测.从NH(α~1△)的影像可以发现对于大部分的~1NH(v|j)产物,CO的振动分布是反转的.各向异性的角分布表明N-C键的断裂是个快速的解离过程.CO(v)的转动分布展现了明显的双峰现象,这一双峰现象应为HNCO经S_1电子态的两种解离途径所致.     

Quasiclassical trajectory theoretical study on the chemical stereodynamics of the O(~1D)+H_2→OH+H reaction and its isotopic variants (HD,D_2)

The quasiclassical trajectory (QCT) method is used to study stereodynamic information about the reaction O ( 1 D) + H 2 →OH + H on the DK (Dobbyn and Knowles) (1 1 A' ) ab initio potential energy surface (PES). A wide scale of collision energy (E c ) from 0.05 eV to 0.5 eV is considered in the dynamic calculations. To reveal the rovibrational excitation effect, calculations at a collision energy of 0.52 eV are carried out for the v = 0 ～ 5, j = 0 and v = 0, j = 0 ～ 15 initial states. The two popularly used polarization-dependent differential cross sections (PDDCSs), dσ 00 /dω t (0, 0) and dσ 20 /dω t (2, 0), and two angular distributions, P(θ r ) and P( r ) are calculated to obtain an insight into the alignment and the orientation of the product molecules. From the calculations, we can obtain that the alignment of the OH product is weaker at high collision energy and becomes stronger with the increase of initial vibrational level, and it is almost insensitive to the initially rotational excitation. Influences of the mass values of isotopes (HD, D 2 ) on the stereodynamics are also shown and discussed. Comparisons between available theoretical results and experimental results are made and discussed.     

The effect of collision energy on the stereodynamics of the reaction H(~2S)+NH(X~3∑~-,v = 0,j = 0)→ N(~4S)+H_2

The quasi-classical trajectory(QCT) is calculated to study the stereodynamics properties of the title reaction H(2S)+NH(X3∑-) →N(4S)+H2 on the ground state 4A' potential energy surface(PES) constructed by Zhai and Han [2011 J.Chem.Phys.135 104314].The calculated QCT reaction probabilities and cross sections are in good agreement with the previous theoretical results.The effects of the collision energy on the k-k' distribution and the product polarization of H2 are studied in detail.It is found that the scattering direction of the product is strongly dependent on the collision energy.With the increase in the collision energy,the scattering directions of the products change from backward scattering to forward scattering.The distribution of P(θr) is strongly dependent on the collision energy below the lower collision energy(about 11.53 kcal/mol).In addition,the P(φr) distribution dramatically changes as the collision energy increases.The calculated QCT results indicate that the collision energy plays an important role in determining the stereodynamics of the title reaction.     

The reagent vibrational excitation effect on the stereodynamics of the reaction O(~1D)+HBr→OH+Br

Calculations on the dynamics of the reaction O( 1 D) + HBr → OH + Br are performed on the ab initio potential energy surfaces (PESs) of the ground state given by Peterson Peterson K A J. Chem. Phys. 113 4598 (2000)using the quasiclassical trajectory (QCT) method. The product distribution of the dihedral angle, P (φ r ), and that of the angle between and , P (θ r ), are presented in three dimensions. Moreover, we also investigate the reagent vibrational excitation effects on the two polarization-dependent generalized differential cross sections (PDDCS), PDDCS 00 and PDDCS 20 , in the center-of-mass frame. The results indicate that the vector properties are sensitive to the reagent vibrational quantum number.     

Accurate calculation of the potential energy curve and spectroscopic parameters of X~2Σ~+ state of ~(12)Mg~1H

High level calculations on the ground state of12Mg1 H molecule have been performed using multi-reference configuration interaction(MRCI) method with the Davidson modification. The core–valence correlation and scalar relativistic corrections are included into the present calculations at the same time. The potential energy curve(PEC) of the ground state, all of the vibrational levels and spectroscopic parameters are fitted. The results show that the levels and spectroscopic parameters are in good agreement with the available experimental data. The analytical potential energy function(APEF) is also deduced from the calculated PEC using the Murrell–Sorbie(M–S) potential function. The present results can provide a helpful reference for the future spectroscopic experiments or dynamical calculations of the molecule.     

The effect of the rotational excitation of NO on the stereodynamics for the reaction C(~3P)+NO(X~2Π)→CN(X~2Σ~+)+O(~3P)

The stereodynamic properties of the reaction C(3P)+NO(X2Π)→CN(X2Σ+)+O(3P) in different rotational states of reactant NO are studied theoretically by using the quasiclassical trajectory method on 2A' and 2A' potential energy surfaces(PESs) at a collision energy of 0.06 eV.The vector properties in different rotational states on the two surfaces are discussed in detail.The results indicate that the rotational excitation of NO has considerable influence on the stereodynamic property of the reaction occurring on the two surfaces.At the same time,the calculated polarization-dependent differential cross sections(PDDCSs) in different initial rotational states manifest that products are strongly polarized at three scattering angles.