量子反应散射理论及其应用

用交叉分子束和激光技术能够获得从反应物到产物化学变化过程中全部微观的、动态的知识,从而把化学反应动力学发展到基元反应的态态层次.量子反应散射理论能够对自然定律所容许的所有基元双分子态态反应作出最完整的描述.对当前分子反应动力学领域常用的几种量子反应散射理论计算方法,如含时波包传播法,紧耦合微分方程法,散射矩阵变分法及排列通道线性组合散射波函数法的原理及其应用作简单介绍,同时对发展动向作出展望.     

F+H2→HF+H反应的全量子态分辨的散射动力学研究

利用高灵敏度的氢原子里德堡飞渡时间谱方法研究了 F H_2→HF H 反应碰撞能在5.02kJ/mol 下的交叉分子束反应态态散射动力学.所有在时间飞渡谱中被观测到的谱峰可以归属为 HF 产物的振转态结构.还观测到了明显的 HF(v’=3)前向散射,以及少许的 HF(v’=2)前向散射.     

低碰撞能下H+HF(v=3,j=0)反应的量子动力学研究

报道了H原子和振动激发的HF(v=3,j=0)分子在低碰撞能下的量子反应动力学研究.计算结果表明:在低碰撞能下,散射主要以非反应过程为主;振动激发有利于反应的进行;在小于10-4eV碰撞能下,非反应非弹性散射截面和反应截面的比值约为3.在反应截面上发现了Feshbach共振现象,证实是由反应通道上紧邻反应势垒的H…HF(v=3,j=1～3)的范德瓦尔斯聚合体存在的准束缚态所形成.     

高里德伯态氢原子与氢分子的全量子态分辨的散射动力学研究:费米模型的精确性

文章描述了高里德伯态氢原子与氘分子（D2）散射的近期研究结果。实验研究表明，在高里德伯态氢原子与D2的散射中，非弹性散射和化学反应散射都是重要的。在非弹性散射过程中，氘分子的核自旋是守恒的。反应散射结果说明，高里德伯态氢原子与氘分子的散射动力学和质子与氘分子的散射动力学是非常类似的．这一结果表明，费米的独立碰撞模型在态-态散射动力学的层次上也是正确的。     

F+HCl/DCl反应散射的量子含时波包

在Deskevich等人最近构建的势能面上，利用量子含时波包方法，研究了F+HCl/DCl的反应散射动力学．在总角动量J=0的情况下，得出了这两个反应具有不同初始振转态条件下的总反应几率．计算结果表明，对于这两个反应，反应物的转动激发态可以明显的提高反应几率，对于F+HCl反应这种提高尤其明显．而振动激发只是对降低碰撞能反应阈值有帮助，对总的反应几率几乎没有任何影响．另外，这两个反应的进行途径有明显的转动自由度部分．在含有较轻的氢原子的F+HCl反应中，总反应几率中所呈现的量子共振和隧穿效应较之F+DCl     

趋向态分辨的微分截面测量：值得费这么大的劲儿吗？

简要地综述最近其实验室在用态分辨微分截面测量基元双分子化学反应方面所做出的努力。特别是集中讨论了Ｓ（＾１Ｏ）和Ｏ（＾１Ｏ）与Ｈ２的两个典型插入式反应。目的是要探索通常被形成络合物反应的统计描述藏起来的详细动力学特性。这两个反应的比较也对当前一个非直接反应的概念性的理解做尖锐的测试。     

与HO_2和HO_3相关的复杂反应的量子动力学（英文）

形成复合物的复杂反应广泛存在于气相化学反应中.对形成复合物的双分子复杂反应的研究揭示了一些有趣的动力学现象.这类反应在反应入口通道通常只有很低的反应能垒或者没有能垒,且反应路径上存在深势阱,使得它们的动力学特征与直接反应有显著区别.理论上,量子态分辨的反应动力学研究可以为化学反应提供最详细的微观机制,目前量子动力学研究己成功地应用于含有单个势垒的直接反应.但对于包含深势阱、多通道的多原子复杂反应体系,构建高精度的势能面并进行精确的量子动力学计算仍然充满挑战.本文综述了在燃烧、大气和星际化学中至关重要的与HO_2和HO_3相关的典型复杂反应的最新研究进展,介绍了到目前为止这两个体系在理论和实验方面的研究工作,着重总结了这些体系的实验和理论研究成果中仍未解决的动力学问题.     

H+HD→H2+D反应的高分辨交叉分子束实验研究

本文利用交叉分子束方法和离子速度成像技术,对H+HD→H₂+D反应在1.17 eV碰撞能下的态-态反应动力学开展了高分辨实验研究. 实验采用1+1''(真空紫外+紫外)近阈值激光电离方式对反应中的D原子产物进行探测,获得了高角度分辨和高能量分辨的产物离子速度影像,进而精确获得了反应的态-态微分截面. 实验观测到了H₂(v''=0,j''=1)和H₂(v''=0,j''=3)振转产物角分布中与散射过程的干涉效应相联系的前向散射振荡. 这一研究进一步表明了化学反应微分截面的精确测量在气相态-态反应动力学研究中的重要性.     

二甲醚/空气对向流扩散燃烧反应历程的数值研究

本文采用详细化学反应动力学模型对二甲醚对向流扩散燃烧火焰进行了数值模拟,通过分析二甲醚燃烧过程中基元反应速度、关键中间产物和自由基,得到了二甲醚在对向流扩散燃烧中氧化的主要反应途径.结果表明,反应主要发生在高温区域(大于 800 K),CH2O、H2 和 CH4是重要的中间产物;OH、H 和 CH3是重要的自由基,在生成 CO、CO2和 H2O 的过程中起到关键性作用.     

玻色-爱因斯坦凝聚领域Feshbach共振现象研究进展

Feshbach共振现象是当前玻色一爱因斯坦凝聚领域中的一个研究热点．目前在大多数低温碱金属原子气体里都已观测到Feshbach共振现象．在实验里利用Feshbach共振可以任意改变这些系统中原子之间的相互作用强度，从强相互排斥作用到强相互吸引作用都可以实现．文章详细介绍Feshbach共振现象以及目前它在原子气体系统里的最重要的两个应用，研究费米子气体里的超流态和有强相互作用的玻色子气体．     

Formation of metastable molecular states at the resonance scattering of two atoms in a laser radiation field

Using the Dirac’s method, the formation of metastable molecular states at the resonance scattering of two atoms in the laser radiation field is considered. Expressions for the metastable level populations and the resonance scattering cross sections are obtained. In the case of an exact resonance with the laser radiation, the graphs for populations and resonance scattering cross sections, which have two peaks due to the Autler–Townes effect, are obtained. These results play an important role in the study of the controlled chemical reaction and for the understanding of the processes in the quantum systems of the Bose–Einstein condensate at low temperatures, as well as in the various optical processes in atomic gases.     

Structural control of Fano resonances in semiconductor heterostructures

Structural control of quantum interference in the optical intrasubband absorption spectrum of GaAs/AlGaAs multi-quantum wells is investigated theoretically. Our study shows that pronounced Fano resonances are in general difficult to obtain in quantum well heterostructures, with a presence of distinct Fano resonance features being the exception rather than the rule. Guided by an analogy to Young’s double-slit experiment, we design increasingly improved structures to display Fano resonances. Best results are achieved in structures where there is strong overlap between the ground-state wavefunction and scattering states associated with the uncoupled continuum. Alternatively one may use ionization via two or more resonances. In this case, resonances should not be separated by more than 25 meV to give significant effects. Moreover, we show that resonance features may also be induced without potential barriers to a continuum merely via orthogonality between bound and excited states.     

Standard deviations of chemical reaction rates and validity ranges of the statistical theory

Validity ranges of the statistical theory of chemical reactions are discussed. On the basis of the quantum mechanical scattering theory, the rate of the chemical reaction of the complex-formation mode is formulated. The interaction matrix elements between resonance states and scattering continua are regarded as stochastic variables. The expectation value of the reaction rate is shown to coincide with the prediction of the conventional statistical theory if the condition of overlapping resonance is fulfilled. The standard deviation is found to be inversely proportional to the number of resonance states involved in the width of the collision energy. High density of vibrational energy levels of the collision complex serves to suppress the standard deviation and to make the statistical theory accurate. The condition for the conventional statistical theory to hit the correct value with probabilities more than 99% is obtained as a relation between the number of vibrational modes and the depth of the potential energy well of the collision complex.     

二元溶液中基频拉曼散射系数随浓度变化对费米共振的影响

在二硫化碳(CS₂)和苯(C₆H₆)的二元溶液中,随着相对体积浓度而变化,C₆H₆的基频ν_１(992 cm-1) 的拉曼散射系数随浓度减小而增加,而CS₂的基频ν₁(656 cm-1)的拉曼散射系数则随浓度增加而增加。文章测量了这二元溶液相对不同体积浓度的拉曼光谱。结果表明,尽管CS₂和C₆H₆的基频ν₁的强度都随着浓度变化而发生较大变化,但C₆H₆的基频ν₁对其参与的ν₁+ν₆～ν₈费米共振几乎没有影响,而CS₂的基频ν₁强度的变化不仅对ν₁～2ν₂费米共振产生较大影响,还使基频ν₂发生变化。文章给出了实验结果,并用Bertran费米共振理论和群论给予了解释。     

Multichannel calculation of D*s vector states and the D+sJ(2632) resonance

We study bound states below threshold and resonances above threshold in the D0K+ and D(+)(s)eta systems, using a many-coupled-channel model for nonexotic meson-meson scattering applied to states with the quantum numbers of cs quark-antiquark vector mesons. We fit the ground state at 2.112 GeV, whence the lowest resonances in D0K+ come out at 2.61, 2.72, 3.03, and 3.08 GeV. The resonance at 2.61 GeV acquires a width of about 8 MeV, while its partial P wave cross section is up to 6 times larger in D(s)eta than in D0K+, provided a mechanism accounting for Okubo-Zweig-Iizuka-forbidden decays is included. The latter finding is in agreement with the observations of the SELEX Collaboration with respect to the recently reported D(+)(sJ)(2632) resonance. Therefore, we conclude that the D(+)(sJ)(2632) is probably the first recurrence of the D(*)(s)(2112) meson.     

丝氨酸异构体的电子-分子形状共振态及其解离动力学理论研究

Shape resonances of electron-molecule system formed in the low-energy electron attachment to four low-lying conformers of serine (serine 1, serine 2, serine 3, and serine 4) in gas phase are investigated using the quantum scattering method with the non-empirical model potentials in single-center expansion. In the attachment energy range of 0-10 eV, three shape resonances for serine 1, serine 2, and serine 4 and four shape resonances for serine 3 are predicted. The one-dimensional potential energy curves of the temporary negative ions of electron-serine are calculated to explore the correlations between the shape resonance and the bond cleavage. The bond-cleavage selectivity of the different resonant states for a certain conformer is demonstrated, and the recent experimental results about the dissociative electron attachment to serine are interpreted on the basis of present calculations.     

On meson resonances and chiral symmetry

We study meson resonances with quantum numbers J^P=1⁺ in terms of the chiral SU(3) Lagrangian. At leading order a parameter-free prediction is obtained for the scattering of Goldstone bosons off vector mesons with J^P=1⁻ once we insist on approximate crossing symmetry of the unitarized scattering amplitude. A resonance spectrum arises that is remarkably close to the empirical pattern. In particular, we find that the strangeness-zero resonances h₁(1380), f₁(1285) and b₁(1235) are formed due to strong and channels. This leads to large coupling constants of those resonances to the latter states.     

超冷温度下钾和铯原子间弹性散射特性的精确计算

本文分别用量子方法和半经典方法计算了超冷钾和铯原子之间弹性碰撞的s波散射长度,有效力程和p波散射长度等散射参数. 超冷温度下³⁹K-¹³³Cs原子间的弹性散射截面主要为s波贡献,随着碰撞能量的增加散射截面有丰富的形状共振出现, 计算发现单重态和三重态截面分别存在显著的g波和d波形状共振.另外,本文应用简并内态近似方法获得了⁴¹K-¹³³Cs 超精细态相互作用时的s波散射长度.     

Quantum collinear reaction probabilities for vibrationally excited reactants : F+H2(v≤2)→FH(v′≤5)+H

Quantum mechanical reaction probabilities are reported for the collinear reaction F+H₂(v)→FH(v′)+H in an energy range where two or three vibrational H₂ states v are open. Rotated Morse-cubic spline representations of the extended LEPS surfaces Muckerman I and V, and an adaptation of the BOPS SCFCI surface have been used. The scattering is dominated by resonances. A detailed investigation of the different kinds of resonance behaviour is presented. For the two LEPS surfaces, overall features of the reaction probability curves can be correlated qualitatively in a one-to-one manner. Differences between the BOPS and LEPS reaction probabilities are more pronounced for v=1 than for v=0. For all surfaces, effects of vibrational excitation show a much more systematic behaviour in terms of the reverse reaction than for the forward reaction. A multi-step mechanism is deduced for the reaction, and an attempt is made to give an interpretation in terms of physical concepts including centrifugal effects, Franck-Condon transitions and quasibound states. No obvious simple trends emerge from a surprisal analysis. Most surprisal plots are markedly non-linear in the energy range considered.     

复动量格林函数方法对n-α散射研究

在复动量表象下引入格林函数,建立了复动量格林函数方法.把这种方法应用于n-α散射系统,计算其散射相移.提取n-α系统的共振态并研究共振态对能级密度、相移和散射截面的贡献.在不引入任何非物理参数的前提下,离散化薛定谔积分方程得到束缚态、共振态和连续谱.通过分析散射态物理量可以更好地理解共振态以及非共振连续谱态.在n-α系统中的成功应用,证明了该方法的正确性.