Intrinsic product polarization and branch ratio in the S(~1D,~3P)+HD reaction on three electronic states

The intrinsic product polarization and intramolecular isotope effect of the S(~1D,~3P) + HD reaction have been investigated on both the lowest singlet state(1A) and the triplet state(3A and 3A) potential energy surfaces by using quasi-classical trajectory and quantum mechanical methods.The calculations indicate that intramolecular isotope effects are different on the three electronic states.The stereodynamics study shows that the P(θr) distributions,P(φ r) distributions,and polarization-dependent differential cross sections(PDDCSs)(00) are sensitive to mass factor and the product angular momentum vectors are not only aligned but also oriented.     

碰撞能和同位素取代对H+BrF→HBr+F反应立体动力学影响的理论研究

基于拟合得到的London-Eyring-Polanyi-Sato势能面,运用准经典轨线方法对H+BrF→HBr+F反应的立体动力学性质进行了理论研究.计算了反映矢量相关的角分布和对光诱导的双分子反应实验敏感的四个极化微分散射截面.结果表明:随着碰撞能的增加,产物的转动极化变强,并且产物的后向散射占主导地位.通过比较D+BrF→DBr+F和H+BrF→HBr+F反应的产物极化,揭示了明显的同位素效应.     

甲基自由基在212.5 nm的光分解:母体内能态的激发对产物态分布的影响

利用里德堡氢原子飞渡时间谱的方法,进行了甲基自由基在212.5nm 的光解动力学的实验研究.甲基自由基来自于碘甲烷分子在266nm 的光分解.实验测量了不同振动态的甲基自由基通过3s 电子激发态解离的产物 CH_2自由基的平动能分布和角分布,并从平动能分布得到了 CH_2自由基的转动布居.实验同时详细地研究了母体分子甲基自由基的振动和转动激发对光解动力学的影响.实验结果表明母体分乙甲基自由基的伞形振动对于产物的转动激发和角分布均有较大的影响,而母体分子的转动激发只对产物的角分布有较明显的影响.     

Isotope effect on the stereodynamics for the collision reaction H＋LiF（v = 0, j = 0） → HF＋Li

Stereodynamics for the reaction H+LiF(v=0, j=0) → HF+Li and its isotopic variants on the ground-state (1 2 A′) potential energy surface (PES) are studied by employing the quasi-classical trajectory (QCT) method. At a collision energy of 1.0 eV, product rotational angular momentum distributions P (θr), P (φr), and P (θr ,φr), are calculated in the center-of-mass (CM) frame. The results demonstrate that the product rotational angular momentum j′ is not only aligned along the direction perpendicular to the reagent relative velocity vector k, but also oriented along the negative y axis. The four generalized polarization-dependent differential cross sections (PDDCSs) are also computed. The PDDCS 00 distribution shows a preferential forward scattering for the product angular distribution in each of the three isotopic reactions, which indicates that the title collision reaction is a direct reaction mechanism. The isotope effect on the stereodynamics is revealed and discussed in detail.     

Reactive scattering of a supersonic oxygen atom beam O+ICl

Reactive scattering of O atoms with ICl molecules has been studied at an initial translational energy E = 40 kJ mol^-1 using a supersonic beam of O atoms seeded in He and at E = 15 kJ mol^-1 using O atoms seeded in Ne. Velocity distributions of OI product were measured by cross-correlation time-of-flight analysis. Full contour maps of the differential reaction cross-section have been obtained which show peaking almost equally in the forward and backward directions at both initial translational energies. The product translational energy distributions are consistent with a long-lived O-I-Cl collision complex dissociating via a loose transition state. The stability of the O-I-Cl complex is attributed to the low electronegativity of the central I atom compared with the peripheral atoms. This electronegativity ordering rule also determines the stability of the intermediates in the other reactions of oxygen atoms with halogen molecules. The mild peaking of the product angular distributions for O + ICl and IBr indicates that collision complexes have quite modest collision angular momenta L ～ 40 ? corresponding to impact parameters b ～ 1·4 Å and that the angular momentum of the OI molecule in the loose transition state may be approximately half the product orbital angular momentum.     

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     

Experiment and theory for the 2H(e,p)e′n reaction

Differential cross sections and angular distributions of protons from the ²H(e, p)e′n reaction have been measured at four incident electron energies. The proton angular distributions were measured with the neutron-proton relative energy approximately constant, and an 85° differential cross section was measured as a function of the incident electron energy. The electrodisintegration cross section was calculated using the Hulthén wave function for the ground state with a plane wave for the final state. Reasonable agreement between experiment and theory is found.     

Direct surface-transfer reaction to the continuum states induced by a 1760 MeV 40Ar beam on 27Al and natTi target nuclei

The inclusive energy spectra of few-nucleon transfer reactions obtained by bombarding ²⁷Al and ^natTi target nuclei with the GANIL 1760 MeV ⁴⁰Ar beam have been analysed in terms of direct surface-transfer reactions populating the continuum states. The shape at forward angles of the various energy spectra and the corresponding angular distributions are well reproduced by a diffractional model calculation based on mutual excitation of the two residual partners. It turns out that one of the essential ingredients of the calculations is the Williams partial level density either of the target or of the projectile constructed only with the transferred nucleons or residual holes coupled to the ground state.     

间-吡啶基紫外光化学中的氢原子解离通道

利用高里德堡态氢原子飞行时间探测技术, 在224～248 nm激发波长研究了间-吡啶基紫外光化学中的氢原子解离通道的动力学过程．氢原子光解碎片产率谱显示在234 nm附近有较宽的吸收．产物的平动能释放较小;在224～248 nm激发波长区间平均< f_T>是0.12～0.19．产物的平动能分布显示产物是H+HC≡C-CH=CH-C≡N,H 3,4-吡啶和H 2,3-吡啶,以H HC≡C-CH=CH-C≡N为主要的氢原子生成通道．氢原子碎片具有各向同性的角度分布．研究结果表明,在紫外电子态激发以后,间-吡啶基经过内转换到电子基态,再经由单分子解离到H HC≡C-CH=CH-C≡N,H 3,4-吡啶和H 2,3-吡啶产物．间-吡啶基的紫外光解机理和以前报道过的邻-吡啶基的紫外光解机理相似．     

Quasi-classical trajectory approach to the O（1D）＋HBr ）OH＋Br reaction stereo-dynamics on X1A＇ potential energy surface

The vector properties of reaction O(¹D)+HBr→ OH+Br on the potential energy surface (PES) of X¹A′ ground singlet state are studied by using the quasi-classical trajectory (QCT) theory. The polarization-dependent differential cross sections (PDDCSs), the average rotational alignment factor 2(j′· k)>, as well as the distributions reflecting vector correlations are also computed. The analysis of the results shows that the alignment and the orientation distribution of the rotation angular momentum vector of product molecule OH is influenced by both the effect of heavy-light-heavy (HLH) type mass combination and the deep well of PES.     

Heavy-ion reactions on 26Mg

Reactions induced by 126 MeV ¹⁶O ions on ²⁶Mg have been investigated in the angular range 5° to 12°. Optical model parameters were derived from the elastic scattering data and were used in a DWBA analysis of the inelastic scattering and single-nucleon transfer data. Satisfactory agreement was obtained for the angular distributions and for the spectroscopic factors. The two-nucleon transfer reactions appear to excite vibrational states. A DWBA analysis correctly describes the angular distributions for the two-proton transfer data. Most of the other few-nucleon transfer spectra exhibit little selective excitation but give a maximum at an energy consistent with the optimum Q-value predicte for direct transfer. Both the one- and twonucleon transfer data require that the ²⁶Mg ground state contains considerable (λ, μ) = (4. 8) components and is not pure (10, 2) as predicted by simple SU(3) calculations.     

O(1D)和CD4反应的准经典轨线

在新的全域势能面上, 用准经典轨线方法细致地研究了O(¹D)+CD₄多通道化学反应的动力学．这个势能面是用交换不变多项式方法基于MRC+Q/aug-cc-pVTZ从头算点拟合得到的．通过计算得到了产物OD+CD₃、D+CD₂OD/CD₃O和D₂+DCOD/D₂CO的分支比、平动能分布以及角度分布,结果显示理论与实验吻合得较好, 从而说明了这个反应的同位素取代效应很小． 研究表明,O(¹D)+CD₄反应是经过陷入的抽取机理发生的： 最初主要通过D原子的抽取,并不是之前人们认为的直接C-D键的插入形成CD3OD中间物后再进而解离成各个产物通道．     

Polarization of protons from the C(d,p)C reaction

The polarization of protons from the ¹²C(d, p)¹³C reaction has been measured for deuteron bombarding energies between 3.9 and 5.8 MeV. Angular distributions of the polarization for protons leaving ¹³C in its ground state have been measured for laboratory angles between 10° and 135° at several energies in the vicinity of a resonance at 4 MeV in order to determine the effect of that resonance on the polarization. Additional measurements were made at 0.4 MeV intervals throughout the energy range. These measurements demonstrate that the compound-nuclear resonances observed in the cross section do not significantly alter the polarization angular distributions except at back angles. The shape of the observed polarization angular distributions at all energies is quite similar to previous results obtained for deuteron bombarding energies up to 15 MeV.     

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.     

Proton-neutron correlation in the deuteron breakup at 56 MeV and prior-form DWBA analysis

Proton-neutron angular correlations in the ¹²C, ⁵¹V and ¹¹⁸Sn(d, pn) reactions have been measured at 56 MeV to investigate the deuteron breakup process. The elastic breakup which leaves the target nucleus in its ground state dominates the coincident spectra. The elastic breakup cross sections are estimated to be 36–48% of the inclusive breakup yields at 15° or 17.5°. In the angular correlations the protons are emitted predominantly on the side of the beam opposite to the neutrons. The experimental data have been analyzed using the prior-form DWBA. For both nuclear and Coulomb breakup, sufficient convergence of the calculations is obtained by including the pn angular momenta up to l = 2. For the nuclear breakup calculations, the l = 0 and 2 contributions dominate the cross sections. For the Coulomb breakup the l = 1 contribution is predominant. In the calculations the effect of the Coulomb breakup is seen at forward angles of the angular correlation. The DWBA calculations reproduce fairly well the coincident energy spectra and the angular correlations in the angular region where the protons are emitted on the side of the beam opposite to the neutrons. On the other hand the calculations overestimate the break-up cross sections by a factor of 2 to 10 in the angular region where the protons are emitted on the same side of the beam as the neutrons. The distributions of deuteron c.m. angular momenta that contribute to the breakup amplitude are examined to obtain information on the region of space in which the breakup reactions takes place.     

A study of the 2H(d,p)3H AND 2H(d,n)3He reactions and the excited state of 4He at 23.9 MeV

The relative differential cross sections have been measured for the ²H(d, p)³H and the ²H(d, n)³He reactions from 300 keV to 700 keV in 50 keV steps. Angular distributions of all charged particles from the reactions were taken from 20° to 160° in the laboratory system. Energy-dependent asymmetry coefficients from the expansion of the centre-of-mass angular distributions in terms of even powers of cos θ were obtained as were the branching ratios between the two reaction modes. The different energy dependences of the moments of the two cross sections were used to test the need for the existence of a recently reported T = 0 state in ⁴He.     

HN3分子在190-248 nm的紫外光分解动力学

利用氢原子里德堡态飞行时间谱技术研究HN3分子在紫外光(190?248 nm)光照射下的H+N3通道的光解动力学结果．通过测量H+N3通道的产物平动能分布以及产物的角分布，得到了在不同波长光解下N3产物分子的振动态分布． 实验结果表明， 在大于225 nm时，HN3分子主要是通过一个排斥态解离的．而在低于225 nm时，有一个慢的通道从220 nm 开始出现．这一新的解离通道是一个闭环产生环状N3产物的通道．当光解能量增加时，这一新通道相对的变得越来越重要．     

Eu原子4f~76p_(3/2)ns自电离衰变分支比和弹射电子角分布

首先运用孤立实激发技术将Eu原子从基态4f~76s~(28)S_(7/2)经中间态4f~76s6p共振激发到4f~76sns Rydberg态,然后再将其进一步激发至4f~76p_(3/2)ns(n=7,8)自电离态.其次,采用速度影像技术对Eu原子自电离弹射出的电子进行探测,以便来研究自电离衰变分支比和弹射电子角分布.在研究自电离衰变分支比时,重点讨论了粒子数反转的可能性,并依据此现象可为实现自电离激光器提供有价值的信息.另外,还探讨了各向异性参数对弹射电子角分布的影响;以及在Eu原子不同自电离几率位置处,讨论了弹射电子角分布形状的变化情况.     

以交叉分子束及时间切片离子速度成像法研究产物成对相关讯息

研发了一种新颖的实验方法 ,用以在交叉分子束条件下测量双分子反应产物的成对相关 (paircorrela tion)讯息 .作为尝试 ,首先选取了F +CD4/CHD3 /CH4反应体系 .结合时间切片离子速度成像与交叉分子束技术 ,可直接测得产物态分辨且成对相关的角分布 .已研究了产物成对相关的几个方面 ,阐释了碰撞能效应 .测量表明 ,产物角分布对HF/DF产物振动态有极强的相关性 ,同时对甲基产物的振动态也有不可忽视的相关性 .在低碰撞能时 ,在F +CH4多原子反应中 ,首度发现了反应动态共振的证据 .