Xe对NO(X)微分截面和非弹性散射中的碰撞诱导旋转准直（英文）

本文对NO(X)-Xe碰撞系统在碰撞能量为519 cm~(-1),测量了完全A-双峰分解的微分截面和碰撞引起的旋转准直力矩.同时结合初始量子态选择,使用六极杆的非均质电场,借助量子态分辨的测量,利用(1+1')共振增强的多光子电离和速度离子成像.结果显示,微分截面以及偏振相关的微分截面均显示与从头算势能面上进行的量子力学散射计算[J.Klos et al.J.Chem.Phys.137,014312 (2012)]一致.通过与准经典轨迹、硬壳势能的量子力学散射以及运动近端模型的比较,评估了势能对所测微分截面和碰撞引起的旋转准直力矩的影响.     

交叉分子束实验研究F+D2(v=1, j=0)反应

本文使用交叉分子束方法研究了氟原子和振动激发态氘分子D₂(v=1, j=0)的反应. 使用受激拉曼抽运的方法制备了振动激发的D₂分子. 实验中未观测到来自于旋轨耦合激发态氟原子F^*(²P_1/2)与振动激发态D₂分子的贡献. 观测到来自于旋轨耦合基态氟原子F(²P_3/2)和振动激发态D₂的反应信号,相应的产物DF分子布居于v''=2,3,4,5振动态上. 与振动基态反应F+D₂(v=1,j=0)相比,振动激发态反应F+D₂(v=1,j=0)生成的DF产物转动分布更“热”. 获得了振动激发反应的四个碰撞能在0.32至2.62 kcal/mol范围内的微分反应截面. 在最低的碰撞能0.32 kcal/mol下,所有振动态的DF产物都以后向散射为主. 随着碰撞能的增加,DF产物的角分布逐渐从后向转移到侧向. 测量了DF(v''=5)产物的前向微分散射截面随碰撞能变化的曲线. 前向散射的DF(v''=5)信号出现于1.0 kcal/mol. 在2.62 kcal/mol碰撞能下DF(v''=5)主要为前向散射.     

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.     

碰撞能44∽164 cm−1范围内单量子态转动激发对F+D2反应的影响

当碰撞能很低,尤其是远低于反应势垒的时候,反应通常经过量子隧穿来进行. 目前,还没有明确的物理图像来描述反应物的转动激发对这类反应过程的影响. 本文基于里德堡态D原子飞行时间谱探测方法,利用多通道探测器交叉分子束装置研究了碰撞能44 cm^-1∽164 cm^-1下反应F+D₂(v=0,j=0,1)→DF(v'')+D的动力学过程,并得到了振动态分辨的微分截面. 在可资用能相等时,通过调控反应的平动能,研究了D₂转动激发对于反应的影响,发现反应物的转动比平动更有利于反应的进行. D₂的转动激发导致产物DF的角分布和量子态分布发生显著变化. 本工作进一步加深转动激发对于反应的影响的理解,尤其是在反应能量远低于反应势垒的情况下.     

羟基自由基双光子激发解离动力学

本文利用高里德堡态氢原子飞行时间探测技术，研究了羟基自由基的双光子激发解离动力学. H(²S)+O(¹D)和H(²S)+O(¹S)解离通道是由于羟基在经由A²Σ⁺(v''=2, J''=0.5-2.5)中间态通过双光子激发最终到排斥性的激发态势能曲线2²Ⅱ和B²Σ⁺上产生. 这两种解离通道产物都具有各向异性的角向分布，其中H(²S)+O(¹D)产物角分布异向因子β为-0.97，H(²S)+O(¹S)产物角分布异向因子β为1.97. 各向异性的角向分布与OH自由基在排斥性的激发态势能曲线上直接解离机理相吻合. 此实验观测到羟基自由基的解离能为35580±15 cm^-1.     

H+Br2→HBr+Br反应的态-态量子动力学研究

H原子与卤素气体(F₂,Cl₂,Br₂)的反应是典型的轻-重-重原子-双原子反应. 对于研究化学激光的基本反应途径十分重要. 之前所有的实验结果都表明,H+Br₂→HBr+Br反应的势垒高度很小,甚至是负值. 本文基于11698个UCCSD(T)/CBS水平的从头算能量点,用FI-NN方法构建了HBr₂体系的精确全维全域势能面,还包括了Br原子²P_3/2轨道的自旋-轨道耦合. 势能面有一个下沉的势垒(-0.351 kcal/mol}),放热(ΔH₀=-41.265 kcal/mol) 和实验值吻合的很好,在这个势能面上应用含时波包方法计算了H+Br₂→HBr+Br反应的态-态积分和微分截面. 对初始基态反应,产物HBr(v′=2,3,4)态在所考虑的整个能量范围内占主导地位,说明HBr是振动态布居反转的. 温度300 K时,计算的产物振动分布在$v$$''$=3有最大值,在v′=0,1的分布可以忽略不计,这与Setser及合作者和Polanyi及合作者的实验结果相一致. 超过一半的总可用能量进入到产物的内部运动中,这其中大部分进入到振动中. 计算表明,反应物Br₂的初始转动激发对产物振转态分布和微分截面影响很小,而初始振动激发则有一定影响. 在低能区域,初始振动激发到v₀=5态很明显的增强了产物的振动激发. 在初始基态和初始转动激发态下,碰撞能量到0.5 eV的微分截面在后向达到峰值,但随着碰撞能量的增加,角分布的宽度显著增加. 对于初始振动激发态,产物微分截面的结构较为复杂,对高振动激发态产物有很强的前向散射峰.     

Ne同位素替代下Ne-HF碰撞截面的理论计算

采用Huxley势函数拟合QCISD(T)/ aug-cc-pVTZ计算的相互作用势能面,通过精确度较高的密耦近似方法计算了E=100 meV时,氖原子的三种同位素 ¹⁶Ne, ²⁰Ne, ³⁴Ne与HF分子碰撞系统的微分截面和分波截面.探讨了Ne的同位素替代引起的Ne-HF碰撞激发 截面的变化规律.     

HCO基态(X 2A′)与激发态(A 2A'')的全维势能面与吸收光谱

本文利用神经网络方法构建了HCO体系的基态(X ²A'')与第一激发态(A ²A'')的高精度全维势能面. 利用含Davidson修正的内收缩MRCI-F12方法结合非常大的ACV5Z基组,共计算了4624个从头算点,且没有采取任何标度方案. 平衡构型、解离能、振动基频等与实验吻合很好. 与Ndengué等人的此前经标度得到的势能面相比,本文势能面计算的吸收光谱强度略大,峰值位置向更小的能量偏移了几十个波. 结果表明标度势能将会对动力学结果产生一些难以预测的影响. 然而,基于之前标度的势能面计算得到的共振能量比本文的结果更接近实验值,尽管如此,本文新发展的非标度高级别势能面仍有望为之后HCO体系的光解和碰撞动力学的实验和理论研究提供一些理论基础.     

准经典轨线方法研究H(2S)+NO(X2π)→N(4S)+OH(X2π)反应动力学

本文基于精确的势能面,采用准经典轨线方法研究了H(²S)+NO(X²π)→N(⁴S)+OH(X²π)反应的动力学. 对碰撞能量为2.00∽2.80 eV,计算了反应的总反应积分截面,发现它随碰撞能量的增加而单调增加. 特别地,在碰撞能为2.40∽2.57 eV时,计算的反应截面与实验结果吻合. 此外,计算得到的反应速率常数也与实验匹配. 在碰撞能为2.57 eV时,通过对反应轨线的分析,发现该反应由非直接反应主导(是直接反应的1.4倍),揭示了反应在高碰撞能量下的反应动力学特性.     

HOBr/DOBr态到态光解动力学的量子波包研究

本文基于高水平的多参考组态相互作用计算，报导了HOBr的最低三个单重态的三维势能面. 并且对该分子的光解离过程用实波包传播的方法进行了量子动力学研究，不仅计算结果得到了吸收光谱，而且还产生了光解产物的内态和角度分布. 结果与在紫外区域测得的HOBr的总吸收截面定量吻合，并很好的重现了实验上在266 nm处观察到的振动冷和转动热的光解OH/OD产物. 此外，预测了OH/OD的反冲各向异性参数接近平行跃迁的极限值，表明在266 nm处从基态(1¹A'')到2¹A''态的面内跃迁是一个快速的解离过程. 这与实验上从测量转动取向得出的结论一致. 然而，想要实现与实验上的定量一致，还需要考虑自旋和电子角动量的影响.     

Quantum stereodynamics study for the reaction F + HD

This paper studies the quantum stereodynamics of the F + HD(υ = 0, j = 0) → HD + F/HF + D reaction at the collision energies of 0.52 and 0.87~kcal/mol. The quantum scattering calculations, based on Stark-Werner potential energy surfaces, show that the differential cross sections for the HF(υ' = 2) + D and DF(υ' = 3) + H channels are consistent with the recent theoretical results. Furthermore, the product rotational angular momentum orientation and alignment have been determined for some selected rovibrational states of the HF + D and DF + H channels.     

Vibrational and rotational energy transfer of CH+ in collisions with 4He and 3He

A quantum mechanical investigation of vibrational and rotational energy transfer in cold and ultra cold collisions of CH⁺ with ³He and ⁴He atoms is presented. Ab initio potential energy calculations are carried out at the BCCD(T) level and a global 3D potential energy surface is obtained using the Reproducing Kernel Hilbert Space (RKHS) method. Close coupling scattering calculations using this surface are performed at collision energy ranging from 10^-6 to 2000 cm^-1. In the very low collision energy limit, the vibrational and rotational quenching cross sections of CH⁺ in collisions with He are found to be of the same order of magnitude. This unusual result is attributed to the large angular anisotropy of the intermolecular potential and to the unusually small equilibrium value of the Jacobi R coordinate of the He–CH⁺ complex. As for the He–N₂ ⁺ collision, we also find a strong isotope effect in the very low collision energy range which is analyzed in terms of scattering length and the differences between these two collisions are also discussed.     

Differential cross sections from quantum calculations on coupled Ab initio potential energy surfaces and scattering experiments for Cl(2P)+H2 reactions

To assess the relative reactivity of the spin-orbit excited state of atomic Cl with molecular hydrogen, we have measured differential cross sections using an atomic Cl beam with a known concentration of the ground and excited spin-orbit states. These are compared with the first determination of the cross sections from quantum mechanical scattering calculations on a set of coupled ab initio potential energy surfaces. The comparison suggests that these surfaces may underestimate the degree of rotational excitation of the HCl products and that the excited spin-orbit state plays a minor role in the reaction.     

Molekularstrahlmessungen von Stoßquerschnitten für Übergänge zwischen definierten Rotationszuständen zwei-atomiger Moleküle

Inelastic collision cross sections for transitions between specified rotational states designated by (J, M) have been measured in a molecular beam apparatus. With an electrostatic four pole field molecules in a specified rotational state are separated out of a molecular beam and focussed into a gas filled scattering chamber. Molecules which have been scattered by less than 1/2° are then collected in a second four pole field, located directly behind the scattering chamber, and are analyzed for their rotational state. From a comparison of the measured pressure dependence with calculated curves a determination of inelastic collision cross sections for specified quantum jumps is possible. Measured inelastic scattering cross sections for the transitions (2,0→3,0) are reported for the gases He, Ne, Ar, Kr, CH₄, SF₆, H₂, O₂, Air, N₂O, H₂O, CF₂Cl₂. The values range between about 5 and 100 Ų in the order indicated. The scattering gases NH₃ und ND₃ yielded larger cross sections of about 600 Ų and, in addition, the transitions (3,0)→(2,0),(1,0)→(2,0), (2,0)→(1,0) and (3,0)→(1,0) were observed. Total cross sections for the same gases were also measured with the apparatus.     

O~++H_2→OH~++H反应的动力学研究

采用含时量子波包方法结合二阶分裂算符传播子对初始态为(v=0, j=0)的O~++H_2→OH~++H反应体系在0.01—1.00 eV的碰撞能范围内进行了态分辨理论水平上的动力学计算.对反应概率、积分截面、微分截面以及固定初始态的热速率常数等动力学信息进行了计算并与文献报道的实验和理论结果进行了比较.结果表明本文的理论结果与实验结果十分符合.从微分截面的散射信息可知,在低碰撞能范围内,插入反应机制在反应中占据主导地位.随着碰撞能的增加,反应机制逐渐由插入机制变为抽取反应机制.     

使用态-态分辨的量子波包方法对Li+HF/DF反应的研究

使用基于反应物坐标的含时量子波包方法,在APW势能面上,计算了碰撞能在0～0.25 eV范围的Li+HF/DF(v=0,j=0,1)反应的积分和微分截面．同时也计算了初始态选择的反应速率常数．计算结果表明,Li+DF和Li+HF反应产物分布基本类似,只是前者产物转动激发态稍微多些．反应物的转动激发对于Li+DF反应影响很小．这两个反应的微分截面都是前向散射为主的,特别是在碰撞能较高时候．产物振转态分辨的积分截面和后向散射随碰撞能而呈现的振荡现象,可以用来指认Li+HF反应中的共振态．Li+HF的反应速率常数在100～300 K几乎不变,而Li+DF的反应速率常数则增长了10倍左右．Li+HF的反应几率和积分截面和以前报道的结果总体符合较好,差别应该是计算收敛性更好所致．     

Quenching of molecular ions by He buffer loading at ultralow energies: rotational cooling of OH<Superscript>+</Superscript>(<Superscript>3</Superscript>Σ<Superscript>-</Superscript>) from quantum calculations

An ab initio computed potential energy surface is employed to evaluate the interaction of the OH⁺(³Σ ^-) molecule with ⁴He(¹S) atom and an analytic fitting of the raw points is directly employed in quantum scattering calculations at ultralow collision energies. The Hund's case (b) chosen to handle the spin-rotation coupling allows to extract from the numerous inelastic cross sections the relative importance of pure “spin flip" vis-à- vis rotational cooling cross sections. The final rates of all the above processes as a function of the initial |N〉 state are analysed in detail and possible propensity rules are discussed.     

Oscillatory screening and quantum interference effects on electron collisions in quantum plasmas

The oscillatory screening and collision-induced quantum interference effects on electron-electron collisions are investigated in dense quantum plasmas. The modified Debye-Hückel potential with the total spin states of the system is considered to obtain the differential electron-electron scattering cross section in quantum plasmas. It is shown that the electron-electron scattering cross section decreases with an increase of the quantum wave number. In addition, the minimum position of the cross section has been appeared with increasing the collision energy at the scattering angle θL=π/4. It is also found that the oscillatory screening effects strongly suppress the cross section near θL=π/4. In addition, it is found that the quantum interference effects suppress the cross section, especially, for the forward and backward scattering cases.     

Rotational excitation of CH<Subscript>4</Subscript> by He atoms

Quantum close-coupling and coupled-state approximation scattering calculations for rotational energy transfer of rotationally excited CH₄ due to collisions with He are presented for collision energies between 10⁻⁷ and 3000 cm⁻¹ using the MP4 potential of Calderoni et al. [J. Chem. Phys. 121, 8261 (2004)]. State-to-state cross sections and rate coefficients from selected initial rotational states of CH₄ in symmetries A, E, and F are studied from the ultra-cold to the thermal regime. Comparison of the cross sections with available theoretical results and experimental data show good agreement. Applications to astrophysics and cold laboratory environments are briefly addressed.     

He-N2碰撞体系散射截面的理论研究

本文运用量子化学从头计算MP2方法6-311 G(3df,2p)基组,计算了He-N2相互作用的势能,拟合出He原子与N2分子相互作用的各向异性势函数,其势函数参数:势能球平均势阱位置、势阱深度、势能零点位置与通过散射实验数据分析的ESMSV(Exponential-Spline-Morse-Spline-Van der waals)势比较吻合.然后,用公认精确度高的密耦方法计算了He原子与N2分子碰撞体系的总微分截面、弹性微分截面、转动激发的非弹性微分截面和积分截面,计算结果与实验数据符合得较好.