F+H2O/D2O→HF+OH反应的准经典轨迹研究：能垒、反应物转动激发和同位素取代的影响 (cited: 4)

在新构建的含旋轨耦合校正的FH₂O基态势能面上,采用准经典轨迹方法详细研究了F+H₂O/D₂O→HF/DF+OH/OD的反应动态学．氢和氘抽取反应经过较低的类反应物过渡态直接发生反应,生成振动激发的HF/DF和内能较低的OH/OD产物．由于新构建的势能面能垒较低,得到的积分反应截面与实验值吻合．但新势能面对产物态分布和模式选择性影响较小．理论计算结果显示H2O的转动态激发对反应有很强的促进作用,说明其与反应坐标耦合紧密．     

反应N(2D)+H2→NH+H和N(2D)+D2→ND+D的立体动力学理论研究.

基于Ho等人的精确势能面(J. Chem. Phys. 119, 3063(2003))研究,运用准经典轨线方法计算了21.3 kJ/mol碰撞能下反应N(²D)+H₂→NH+H和N(²D)+D₂→ND+D的产物与反应物之间的矢量相关．发现两个反应的产物角分布都是前向和后向呈现峰值分布,产物的转动角动量矢量j′不仅是取向的,而且是在y轴负方向上定向的．两个反应显示出的同位素效应主要归因于同位素质量的差别．     

反应物振动激发对O(3P)+D2→OD+D立体动力学的影响

运用准经典轨线方法,基于Roger的³A"势能面,在碰撞能为104.5 kJ/mol时对O(³P)+D₂反应的立体动力学性质进行了理论研究. 详细讨论与产物矢量相关的的极化分布函数以及四个极化微分反应截面进行了. 结果表明,产物OD的立体动力学性质对反应物分子H_{2相似文献}   

D+OD+反应的量子动力学研究：交换通道和抽取通道的竞争

基于精确的势能面,研究D+OD⁺反应在0.0～1.0 eV碰撞能范围内的量子动力学. 用CS近似(centrifugal sudden approx-imation)的含时波包方法研究吸热的抽取反应通道(D+OD⁺→ O+D₂⁺)和热中性的交换反应通道(D+OD⁺→D+OD⁺),计算两个通道的反应几率、总积分反应截面和热速率常数. 发现在交换反应的反应路径上存在一个凸起结构. 计算的总角动量J=0时的波包分布的含时演化清楚地表明凸状结构对两个通道的动力学有非常重要的影响.     

氘代烷基卤化物CD3CH2F光解动态学的理论研究

在燃烧或大气化学多通道反应中,理解不同产物之间的产品分支比与反应的总速率,对这类基元反应同样重要. 在CCSD(T)/CBS/B3LYP/aug-cc-pVDZ理论水平上,计算所有氘代烷基卤化物CD₃CH₂F物种的基态势能面. 在CD₃CH₂F的解离反应中,C-F键解离反应与分子(HF、DF、H₂、D₂与HD)消除反应存在着争议. 本文使用RRKM方法计算各个步骤的速率常数,并使用稳态方法计算解离产物的相对产物分支比. 在不同的能量下,RRKM方法预测CD₃CH₂F的1,2-消除DF或HF的主要通道是通过四中心过渡态消除,而1,1-消除D₂或H₂的主要通道是通过三中心过渡态消除. 在266、248和193 nm光解时,主产物CD₂CH₂+DF分支比分别为96.57%、91.47%和48.52%;然而,在157 nm光解时,产物分支比计算为16.11%. 基于这些过渡态结构和能量,提出了以下光解离机制：在266、248和193 nm,CD₃CH₂F→吸收光子→TS5→形成产物→CD₂CH₂+DF;在157 nm,CD₃CH₂F→吸收光子→D/F交換的TS1→CDH₂CDF→H/F交换的TS2→CHD₂CHDF→形成产物CHD₂+CHDF.     

O-与CH3CN反应机理的密度泛函理论研究

采用G3MP2B3方法研究了氧负离子与乙腈反应的势能剖面.在(U)B3LYP/6-31+G(d,p)理论水平下分别优化了该反应势能面上反应物、产物、中间体和过渡态的分子结构,采用G3MP2B3方法校正了这些关键点的能量. 势能面上的各个反应路径均通过针对过渡态的內禀反应坐标理论计算加以确定. 分别考察了四个可能的热力学产物通道,即质子转移、氢原子转移、H₂⁺转移和双分子亲核取代反应途径. 其中,经H₂⁺转移生成H₂O的反应通道为该反应的主要产物通道.     

Cl(2P)+D2→DCl+D反应中波恩-奥本海默近似有效性的交叉分子束研究

本文利用高分辨的里德堡态氘原子标识-交叉分子束装置，研究了碰撞能为4.5∽6.5 kcal/mol范围内Cl(²P)[Cl(²P_3/2)和Cl^*(²P_1/2)]与D₂的反应. 虽然自旋轨道激发态反应Cl^*(²P_1/2)+D₂在波恩-奥本海默(B-O)近似下本应是禁阻的，但实验中观测到了该反应的贡献. 通过测量靠近后向的碰撞能相关的微分散射截面连线，发现低碰撞能下的产物主要来自于B-O近似禁阻的反应Cl^*+D₂. 随着碰撞能的提高，自旋轨道基态反应Cl+D₂的反应性增加明显要比自旋轨道激发态反应Cl^*+D₂更快，并且在高碰撞能下成为产物的主要来源. 实验结果表明：在低碰撞能下，Cl^*中自旋轨道激发态的额外能量，可以帮助B-O近似禁阻的反应Cl^*+D₂越过势垒；然而当碰撞能接近和高于反应势垒时，B-O近似允许的反应Cl+D₂占主导地位. Cl/Cl^*+D₂反应中B-O近似有效性的特征与其同位素反应Cl/Cl^*+H₂是一致的.     

对典型多通道反应H+CH3OH的模式特异动力学研究

H+CH₃OH作为典型的多通道反应,在燃烧和星际中起着重要的作用. 本文基于在UCCSD(T)-F12a/AVTZ水平上计算的大量数据点,构建了该体系的全维精确势能面,并基于该势能面,研究了不同产物通道的模式特异动力学. 结果表明,O-H 伸缩、沿C-O轴的扭转以及C$-$H伸缩等模式的振动激发对H₂+CH₃O、H₂+CH₂OH、H₂O+CH₃和H+CH₃OH四个产物通道有着不同的影响. 该研究有助于理解具有多个产物通道的复杂反应的模式特异动力学,进而帮助控制其竞争反应.     

La2Zr2O7:Eu3+纳米棒的合成、表征及其荧光性能

采用传统固相法和水热法成功地制备出棒状La₂Zr₂O₇:Eu³⁺荧光粉. 利用X射线粉末衍射仪、透射电镜和荧光光谱仪等分析了产物的结构、形貌和发光特性. 结果表明红色荧光粉La₂Zr₂O₇:Eu³⁺有良好的晶相,属于立方结构,空间点群为Fd3m; 其形貌主要为纳米棒, 平均直径约47 nm, 长度为50～700 nm. 并对纳米棒的生长机理进行了探讨. 在466 nm蓝光激发下,La₂Zr₂O₇:Eu³⁺荧光粉能发射出Eu³⁺的特征红色荧光,发射主峰位于616 nm处,归属于Eu³⁺的⁵DO_→⁷F2_{超灵敏电偶极跃迁.此外,在产物的发射光谱中能够观察到⁵D}1_→⁷FJ _{(J=0, 1, 2)跃迁和⁵D}1_→⁷FJ _{(J=1, 2, 4)跃迁的劈裂峰,这说明Eu³⁺处在低对称性的晶体场格位中.}     

F−(H2O)+CH3I配体交换反应动力学

本文介绍F^?(H₂O)+CH₃I→[FCH₃I]^?+H₂O在交叉分子束碰撞能量0.3∽2.6 eV的配体交换动力学成像结果. 产物的动能受到弱键结合配合物的稳定性的影响，大量水分子的内部激发不利于中间物有效的能量重新分配，随着碰撞增加，低动能受到抑制. 在0.3 eV时，内部亲核取代非常重要，为形成I^?和I^?(H₂O)的竞争性亲核取代途径提供了依据.     

D+CD4→CD3+D2反应的四维量子散射计算

运用约化维数量子动力学理论，利用含时波包法，对反应D+CD₄→CD_{3+D2进行了四维量子散射计算.将反应多原子CD4看作双原子D—CD 3，反应D+CD4→CD3+D2看作单原子-双原 子反应，把体系的反应简化为四维散射问题. 波函数的传播采用分裂算符法，为避免格点边界处含时波函数的边界反射，采用了光学吸收 势法，在格点边界处引入光学势，消除边界反射.根据CD4分子的C3v对称性， 选取了Jordan和Gilbert提出的半经验势能面.计算结果表明，反应概率随平动能的变化图像 ，呈现出显著的量子共振特性，这是很多提取反应的共同特征.而不同振动态下的反应概率 随平动能的变化表明，随振动量子数的增大，反应概率有明显提高，且反应阈能明显降低， 这说明反应分子的振动能对分子的碰撞反应有重要贡献.而对基态和第一振动激发态时散射 截面的计算，也证明了这一结论.同时，还分别通过计算量子数j，k，m对反应概率的影响， 对该反应的空间取向效应进行了研究，并与H+CH4→CH3+H2反应进行了比较. 关键词： 含时波包 量子散射 反应概率}     

Theoretical study of stereodynamics for the reaction O(3P) +D2 (v=0, j=0) to OD+D and isotope effect

Quasi-classical trajectory (QCT) calculations have been performed to study the product polarization behaviours in the reaction O(³P) + D₂ (v= 0, j= 0)→OD + D. By running trajectories on the ³A′ and ³A″ potential energy surfaces (PESs), vector correlations such as the distributions of the polarization-dependent differential cross sections (PDDCSs), the angular distributions of P(θ_r) and P(ø_r) are presented. Isotope effect is discussed in this work by a comprehensive comparison with the reaction O(³P) + H₂ (v= 0, j= 0) → H + H. Common characteristics as well as differences are discussed in product alignment and orientation for the two reactions. The isotope mass effect differs on the two potential energy surfaces: the isotope mass effect has stronger influence on P(θ_r) and PDDCSs of the ³A′ PES while the opposite on P(ø_r) of the ³A″ potential energy surface.     

Dynamics of reaction of O with H2 and its isotopic variants in different rotational excited states

Scalar properties and vector correlations of the reactions O+H₂ →OH+H, O+HD→OH+D, O+DH→OD+H, and O+D₂ →OD+D at collision energies of 25 and 34.6 kcal/mole have been studied via quasi-classical-trajectory (QCT) method based on a BMS1 potential energy surface (PES). Generalized polarization-dependent differential cross section and the distributions of the dihedral angle at the collision energy of 34.6 kacl/mole are presented. The calculated results indicate that both reagent rotational angular momentum and the mass factor have a significant influence on the scalar properties and vector correlations of the title reactions.     

Direct ab initio molecular dynamics study of F atom reaction with methane

The dynamics of the F + CH₄ → HF + CH₃ and F + CD₄ → DF + CD₃ reactions have been investigated using classical trajectory calculations at the MP2/cc-pvdz level of theory. The trajectories were calculated directly from electronic structure computations, and a Hessian based method with updating was used to integrate the trajectories. Using this method, product rovibrational populations and internal energy distributions were obtained for the F + CH₄ and F + CD₄ reactions. The theoretical results were compared with the available experimental data and previous calculations results. The state distributions of the reaction F + CH₄ in these calculations are in reasonable agreement with the experimental results, which indicates that the experimental behavior of the reaction could be well reproduced by the direct classical trajectory calculations at MP2/cc-pvdz level. As such, the product rovibrational populations and internal energy distributions for the reaction F + CD₄ were predicted. The same degree of agreement between theory and experiment as the F + CH₄ reaction is expected.     

Absolute cross sections and kinetic energy release distributions for electron-impact ionization and dissociation of CD<Superscript>+</Superscript><Subscript>4</Subscript>

Absolute cross sections for electron-impact dissociative excitation and ionization of CD⁺ ₄ leading to formation of ionic products (CD²⁺ ₄, CD⁺ ₃, CD⁺ ₂, CD⁺, C⁺, D⁺ ₃, D⁺ ₂, and D⁺) have been measured. The animated crossed-beams method is applied in the energy range from the reaction threshold up to 2.5 keV. Around 100 eV, the maximum cross sections are found to be (3.8±0.2) ×10^-19 cm²,  cm², (7.1±0.8) ×10^-17 cm², (9.0±0.8) × 10^-17 cm² and (3.7±0.4) ×10^-17 cm² for the heavy carbonaceous ions CD²⁺ ₄, CD⁺ ₃, CD⁺ ₂, CD⁺ and C⁺ respectively. For the light fragments, D⁺ ₃, D⁺ ₂, and D⁺, the cross sections around the maximum are found to be (5.0±0.6) ×10^-19 cm², (1.7± 0.2) ×10^-17 cm² and (10.6±1.0) ×10^-17 cm², respectively. The cross sections are presented in closed analytic forms convenient for implementation in plasma simulation codes. The analysis of ionic product velocity distributions allows determination of the kinetic energy release distributions which are seen to extend from 0 to 9 eV for heavy fragments, and up to 14 eV for light ones. The comparison of present energy thresholds and kinetic energy release with available published data gives information about states contributing to the observed processes. Individual contributions for dissociative excitation and dissociative ionization are determined for each detected product. A complete database including cross sections and energies is compiled for use in fusion application.     

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.     

New FIR laser lines from an optically pumped far-infrared laser with isotopic 13C16O2 pumping

A ¹³C¹⁶O₂ laser optically pumping a FIR laser has resulted in 17 new FIR cw emissions from 78.5 μm to 917 μm. The FIR media were: CD₃OD, CH₃OD, CD₃OH, NH₃ and ¹⁵NH₃. Interesting effects have been observed with a combination of NH₃ and CD₃OD resulting in a new FIR emission. Two new FIR emissions at 181.5 μm and 355.5 μm have been observed with a ¹²C¹⁶O₂ laser optically pumping CD₃OD.     

State-to-state dynamics for O(1D)+D2-->OD+D: evidence for a collinear abstraction mechanism

The O(1D)+D2-->OD+D reaction at two different collisional energies, 2.0 and 3.2 kcal/mol, is investigated by using the H(D) Rydberg "tagging" time-of-flight technique. Experimental results in this study indicate that the OD product is clearly more backward scattered relative to the O(1D) beam direction at the collisional energy of 3.2 kcal/mol. The extra backward scattered OD products are mostly in the highly vibrationally excited states (upsilon = 4,5,6), which is typical of a collinear abstraction mechanism. The experimental results in this work also provide a good testing bed for quantitative theoretical investigations of this benchmark system.     

Mode selectivity in ion–molecule reactions of NH3+

Ammonia ions (NH₃ ⁺) are prepared in two internal states of nearly the same energy, a state with five quanta in the umbrella bending mode (E_int=0.60 eV) and another state with one quantum in the all-symmetric stretch and two quanta in the umbrella bending mode (E_int=0.63 eV). These ions are allowed to react with different neutral reagents, and the product ions are mass analyzed and detected. For each reaction, the product branching ratios are measured as a function of center-of-mass collision energy. Whereas reactions with D₂O, D₂, and CD₄ are found to be uninfluenced by the state preparation of the NH₃ ⁺ reagent, reactions with ND₃, partially deuterated methylamine (CD₃NH₂), and tetrahydrofuran (c-(CH₂)₄O)show varying degrees of mode selectivity, the reaction with tetrahydrofuran to the least extent. We suggest that mode selectivity in these ion–molecule reactions should be a general feature when the charge transfer channel is energetically open, the geometry of the reagent ion differs markedly from the corresponding neutral, and different reaction pathways compete for product production. Received: 14 December 1999 / Published online: 16 August 2000