Reaction functions for weakly bound systems

We propose a new technique to analyze total reaction cross sections. In this technique, which has been previously applied to fusion reactions, the experimental data are used to build a dimensionless reaction function, which does not depend on the system size or details of the optical potential. In this way, total reaction cross sections for different systems can be directly compared. We employ this technique to perform a systematic study of reaction cross sections of weakly bound systems in different mass ranges, and compare their reaction functions with the ones of tightly bound systems with similar masses. We show that breakup reactions and neutron transfers in halo systems lead to large reaction functions, well above the ones of typical tightly or weakly bound stable systems.     

Reaction rate oscillations during CO oxidation over Pt/γ-Al2O3; experimental observations and mechanistic causes

In this paper we present experimental observations of reaction rate oscillations during CO oxidation over Pt/γ-Al₂O₃ at atmospheric pressures. Based on our experimental observations and prior experimental literature on this reaction we propose a mechanistic scheme, which we believe explains in qualitative terms the oscillatory behavior exhibited by this catalytic reaction system. This mechanistic scheme involves a Langmuir-Hinshelwood reaction between adsorbed CO and oxygen and a slow formation and reduction step of an inactive surface oxide species. Our experimental observations and mechanistic ideas, furthermore, support the existence of multiple time scale phenomena for this catalytic reaction system, an idea originally suggested by Chang and Aluko.     

放射性核束引起的奇异核反应研究

结合开展的工作，对放射性核束流引起的核反应总截面研究、放射性束流引起的熔合反应研究、放射性束流开展的天体物理核反应研究以及其它有关的核反应研究进行了评述，并对其可能的发展作了一些探讨 .The study of total nuclear reaction cross section, nuclear fusion reaction,nuclear reaction of astrophysics and related reactions induced by radioactive nuclear beam are reviewed in this paper. The future development of this field is discussed.     

撞击诱导硝基甲烷分子第一步分解反应的动力学计算

本文基于分子温度与压强的关系,计算在不同压强下基态和最低三态硝基甲烷的分子温度,对应计算其沿着CN键裂解反应的热化学和动力学参数.发现基态的硝基甲烷沿着CN键的分解反应是吸热反应,不具自发性,反应转换温度为1550.2 K,平衡常数在80-1202 K温度范围内很低.最低三态的硝基甲烷沿着CN键的裂解是放热反应,反应的Gibbs自由能在80-2558.5 K范围内为负,有好的自发性,且反应较为彻底.298.15-2558.5 K温度范围内反应活化能随着温度的升高而改变,使反应速率随着温度的升高而急剧增大.对应硝基甲烷爆压15 GPa,其分子温度为4617.6 K,该温度下三态分子分解反应的反应速率为1.088×10~8cm~3·mol~(-1)·s~(-1).推算硝基甲烷沿着CN键分解反应混合物的终态温度,当混合物为硝基、甲基和基态的硝基甲烷分子时,反应的终温为1611.37 K,等效能为1676.47 cm~(-1).当混合物为硝基、甲基、基态和最低三态的硝基甲烷分子时,反应的终温为1184.79 K,等效能为1232.65 cm~(-1).两种情况下终态等效能都足以维持硝基甲烷分子沿C-N键裂解反应的发生.这个能量也足以导致混合物中的NO_2分解为NO和O,这与实验检测的结论相一致.     

A thorough understanding of the Diels–Alder reaction of 1,3‐butadiene and ethylene

The Diels–Alder (DA) reaction is one of the most important reactions in organic chemistry. The controversy surrounding this reaction as to whether it follows a concerted or stepwise mechanism has existed for a long time. The reaction of 1,3‐butadiene and ethylene is the paradigmatic example of the DA reaction. We have reinvestigated the mechanism of this reaction using density functional theory. The theoretical study considered all types of possible pathways for the reaction of 1,3‐butadiene and ethylene using six functionals at different rungs of Jacob's ladder. Therefore, a complete picture is given for a thorough understanding of the iconic DA reaction, and a new stationary point during the reaction processes has been reported for the first time. The calculated results indicated that three functionals, ωB97X‐D, M06‐2X, and B2‐PLYP, of the fourth and fifth rungs of Jacob's ladder performed well in the investigation of the mechanism of this reaction and that the reliable basis set should be larger than 6‐311+G(2d,p). The cis‐1,3‐butadiene more easily reacted with ethylene compared with 1,3‐butadiene in the trans conformation. The concerted mechanism was found to be energetically favorable, whose energy barrier is around 10 kcal/mol lower than that of the stepwise mechanism. Two investigated solvents, toluene and CH₃CN, had little impact on this simple DA reaction. Copyright © 2014 John Wiley & Sons, Ltd.     

Development of the reaction time accelerating molecular dynamics method for simulation of chemical reaction

We present a novel and efficient method to integrate chemical reactions into molecular dynamics to simulate chemical reaction systems. We have dubbed this method RTAMD, an acronym for reaction time accelerating molecular dynamics. The methodology we propose here requires no more than the knowledge of the empirical intermolecular potentials for the species at play as well as the elementary reaction path among them. Bond formation during the simulation is performed by changing the inter-atomic potentials from those of the non-bonded species to those of the bonded ones, and a reaction is deemed to occur by the distance separating the bond forming atoms. In this way the energy barrier for a reaction is no longer considered; the estimation of the reaction rate, however, is possible by introducing the principles of the transition state theory. The simplicity of the present scheme to simulate chemical reactions enables it to be used in large-scale MD simulations involving a large number of simultaneous chemical reactions and to evaluate kinetic parameters. In this paper, the basic theory of the method is presented and application to simple equiatomic reaction system where the reaction rates were estimated was illustrated.     

氟分子与乙烯反应的直接动力学模拟

氟分子与乙烯可以发生三类反应，即氟原子排除反应、氟化氢分子排除反应和加合反应，但除了基机制以外，已有的其它机理都不能合理的解释低温下的反应是如何开始的．通过对氟分子与乙烯反应的直接动力学模拟，以密度泛函方法研究了长期困扰的氟分子与乙烯反应的机理．通过计算支持了基机制，轨线模拟细致地描述了三个反应通道．根据此机制对低温池中的反应给出了解释．     

Reversible A↔B reaction–diffusion process with initially mixed reactants: Boundary layer function approach

The reversible A?B reaction–diffusion process, when species A and B are initially mixed and diffuse with different diffusion coefficients, is usually considered as a diffusion-limited process. In this work the reaction rate in such a process is investigated using the boundary layer function method. It was shown that the reaction–diffusion process can be considered as a quasi-equilibrium process. Despite this fact the contribution of the changes in the species concentration of the reaction is comparable to that of the diffusion. Moreover, the ratios of the reaction and diffusion contributions are independent of time and coordinate. The dependence of the reaction rate on the initial species distribution is analyzed. It was demonstrated, for the first time, that the number of the reaction zones is determined by the initial conditions and changes with time. Also the asymptotic long-time behavior of the reaction rate depends on the initial species distribution.     

替代反应法测量锕系核(n,f)和(n,xn)截面

对于某些中子反应截面,在直接测量上存在困难。为了获得那些对核能发展极其重要的核数据,人们提出替代反应法,即利用带电粒子代替中子进行反应,从而实现中子反应截面间接测量的方法。现有替代反应一般采用非弹激发、转移等周边反应,涉及的角动量远比中子反应的大,需要理论修正,这造成了一定的困难。有鉴于此,提出利用轻带电离子的俘获反应作为替代反应,其复合核自旋与中子反应的相当,有效避免了自旋修正的困难。根据这个思路,采用236U的（α,f）和（α,2n）反应作为替代反应,成功提取了239Pu的（n,f）和（n,2n）反应截面,与ENDFB7评价库数据在误差范围内符合较好,表明了替代反应法的优越性,可以在核数据测量中推广应用。There are always difficulties in the direct measurement of reactions induced by neutron, in order to obtain the neutron induced nuclear reaction data which are extremely important for nuclear power development, the surrogate reaction method, which uses charged particles instead of neutron, was proposed. The existing surrogate reaction method generally chooses peripheral reaction as the surrogate reaction, such as inelastic scattering excitation or transfer reaction. As a result, the angular momentum involved is always far larger than the neutron induced reaction, which causes difficulties in the theoretical calculation. Because of this, we proposed to use light-ion capture reaction as the surrogate reaction, the compound nuclei spin is similar with that of the neutron induced reaction, so that the difficulties in spin correction can be effectively avoided. Based on this idea, the 239Pu(n, f) and (n, 2n) reaction cross sections were successfully extracted using 236U(α,f) and (α,2n) reactions as the surrogate reaction. The results coincide well with the data of ENDFB7 within the error range, which shows that the surrogate reaction method has its own superiority, and it can be applied in the measurement of nuclear data.     

LP-FTIR跟踪β-蒎烯与臭氧的气相反应研究

利用ＬＰ ＦＴＩＲ系统跟踪β 蒎烯和Ｏ３的气相反应,研究了β 蒎烯和Ｏ３随反应时间的衰减情况,初步确定了反应中诺蒎酮和甲醛随反应时间的生成情况,定性讨论了反应的可能机理,为进一步的定量分析提供了基础。     

准经典轨线法研究交换反应H(D)+SH/SD的动力学性质

硫在氢气中的燃烧反应在气象化学、燃烧反应和大气污染中都扮演着重要的角色, 近年来一直受到广泛关注, 其逆反应也渐渐成为人们的研究对象. 以Lü 等得到的精确势能面(Lü S J, Zhang P Y, Han K L, He G Z 2012 J. Chem. Phys. 136 94308) 为基础, 用准经典轨线法对交换反应H(D)+SH/SD的动力学性质进行了研究. 计算了包括反应截面、速率常数、不透明函数、产物振动和转动分布等在内 的标量性质和包括产物散射方向、转动角动量定向和取向性质在内的矢量性质. 详细分析了碰撞能量和同位素效应对反应H(D)+SH/SD 的动力学性质的影响. 结果表明, 随着碰撞能量的增加, 反应截面逐渐增大, 产物的后向散射逐渐减弱, 产物转动角动量的取向和定向性质逐渐增强; 另外, 同位素效应对反应的动力学性质也有明显的影响. 以反应动力学性质和势能面为基础, 详细讨论了反应H(D)+SH/SD 的反应机制. 关键词： 准经典轨线 反应截面 速率常数 振动-转动分布     

桑色素荧光法测定痕量锗的反应机理研究

本文对桑色素荧光法测定痕量锗的反应机理进行了较为详细的研究。确定了该反应的络合比，用荧光法，紫外吸收法和红外吸收法确定了反应的位置，从而得到了桑色素荧光法测痕量锗的理论根据。     

三苯基膦和三甲基氯硅烷直接引发丙烯酸乙酯基团转移聚合的核磁共振动力学研究

用FT-NMR的动态³¹P NMR谱及动态¹H NMR谱对用三苯膦(TPP)和三甲基氯硅烷(TMCS)直接引发丙烯酸乙酯(EA)的基团转移聚合(GTP)进行了动力学跟踪,初探了该GTP反应的引发阶段、链增长阶段、链终止阶段的基础反应;三苯膦对丙烯酸乙酯的共轭加成的动力学行为;溴化锌在该反应体系的催化作用等,提出了在这种新的引发体系内的GTP反应历程。     

分子束反应动力学

本文评述分子束反应动力学的进展。首先评述碰撞前反应物的态选择技术,碰撞后反应物的态分析技术,和反应动力学的理论方法和现状;然后评述原子-分子反应动力学和分子-分子反应动力学的进展;最后指出反应动力学的发展趋势和应用前景。     

Ultrasound assisted synthesis of tetrahydrobenzo[c]xanthene-11-ones using CAN as catalyst

Tetrahydrobenzo[c]xanthenes-11-ones was synthesized by a three component reaction of α-naphthol, aromatic aldehyde and dimedone. Ceric ammonium nitrate acts as a suitable eco-friendly catalyst for this method. Shorter reaction duration, mild reaction condition and low cost make this protocol more effective.     

三苯基膦和三甲基氯硅烷直接引发丙烯酸乙酯基团转移聚合的核磁共振动力学研究

用FT-NMR的动态³¹P NMR谱及动态¹H NMR谱对用三苯膦(TPP)和三甲基氯硅烷(TMCS)直接引发丙烯酸乙酯(EA)的基团转移聚合(GTP)进行了动力学跟踪,初探了该GTP反应的引发阶段、链增长阶段、链终止阶段的基础反应;三苯膦对丙烯酸乙酯的共轭加成的动力学行为;溴化锌在该反应体系的催化作用等,提出了在这种新的引发体系内的GTP反应历程。     

Prospects for using the (e,e′γ) reaction to explore nuclear structure

The (e, e′γ) coincidence reaction is considered in detail. The formalism is developed in a way which emphasizes the connection between this reaction and studies of the scattering of (possibly polarized) electrons from polarized nuclei. A wide variety of examples is given to demonstrate the usefulness of the (e, e′γ) reaction for nuclear structure studies and to demonstrate how this reaction serves as both a complement and a supplement to electron scattering from polarized nuclei. Finally, a few cases of special interest are discussed.     

Pattern formation in the thiourea-iodate-sulfite system: Spatial bistability, waves, and stationary patterns

We present a detailed study of the reaction-diffusion patterns observed in the thiourea-iodate-sulfite (TuIS) reaction, operated in open one-side-fed reactors. Besides spatial bistability and spatio-temporal oscillatory dynamics, this proton autoactivated reaction shows stationary patterns, as a result of two back-to-back Turing bifurcations, in the presence of a low-mobility proton binding agent (sodium polyacrylate). This is the third aqueous solution system to produce stationary patterns and the second to do this through a Turing bifurcation. The stationary pattern forming capacities of the reaction are explored through a systematic design method, which is applicable to other bistable and oscillatory reactions. The spatio-temporal dynamics of this reaction is compared with that of the previous ferrocyanide-iodate-sulfite mixed Landolt system.     

Predicting solvent effects in ionic liquids: Extension of a nucleophilic aromatic substitution reaction on a benzene to a pyridine

A nucleophilic aromatic substitution reaction involving a halopyridine electrophile was examined in a series of ionic liquid solvents. This reaction was chosen to test the known solvent effects of ionic liquids on this type of reaction mechanism, previously described with a halobenzene electrophile. The effect of varying the proportion of the ionic liquid in solution was determined, and it was shown that the more ionic liquid present in the reaction mixture, the greater the rate constant enhancement. Temperature‐dependent kinetic analyses yielded activation parameters that showed that the rate constant enhancements are controlled by a balance between enthalpic and entropic effects, depending upon the proportion of ionic liquid present. Overall, the rate enhancement is entropically driven, due to organisation of the ionic liquid about the electrophile. These results are consistent with what has been observed previously for the nucleophilic aromatic substitution reaction involving a halobenzene electrophile, demonstrating that the solvent effects observed for ionic liquids are general for this type of reaction mechanism and opening the possibility for extending their use through rational selection for reaction control.     

F+H2化学反应中的Feshbach共振之研究

化学反应共振态研究是化学动力学研究的重要前沿课题,对于理解基元化学反应的机理有重要的意义.本文中介绍了最近在这一研究方向的重大进展.通过对F＋H2化学反应的全量子态分辨的分子束反应散射实验研究,观测到了F＋H2中反应中明显的反应共振现象.通过高精度的全量子散射动力学研究,发现这一共振现象是由两个Feshbach共振态所引起的,而且这两个Feshbach共振态之间在前向散射有明显的量子干涉效应.这项研究工作使得我们对这一重要基元反应中的化学反应共振态研究向前迈进了一大步。