Phenomenological analysis of the double-pion production in nucleon-nucleon collisions up to 2.2 GeV

With an effective Lagrangian approach, we analyze several NN -> NN pi pi channels by including various resonances with mass up to 1.72 GeV. For the channels with the pion pair of isospin zero, we confirm the dominance of N*(1440) -> N sigma in the near-threshold region. At higher energies and for channels with the final pion pair of isospin one, we find large contributions from N*(1440) -> Delta pi, double-Delta, Delta(1600) -> N*(1440)pi, Delta(1600) -> Delta pi and Delta(1620) -> Delta pi. There are also sizable contributions from Delta -> Delta pi, Delta -> N pi, N -> Delta pi, and nucleon pole at energies close to the threshold. We give a good reproduction to the total cross sections up to beam energies of 2.2 GeV except for the pp -> pp pi(0)pi(0) channel at energies around 1.1 GeV and our results agree with the existing data of differential cross sections of pp -> pp pi(+)p pi(-), pp -> nn pi(+)pi(+), and pp -> pp pi(0)pi(0) which are measured at CELSIUS and COSY.

Observation of charge-dependent azimuthal correlations and possible local strong parity violation in heavy-ion collisions

Parity (P)-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in noncentral collisions. To study this effect, we investigate a three-particle mixed-harmonics azimuthal correlator which is a P-even observable, but directly sensitive to the charge-separation effect. We report measurements of this observable using the STAR detector in Au + Au and Cu + Cu collisions at root s(NN) = 200 and 62 GeV. The results are presented as a function of collision centrality, particle separation in rapidity, and particle transverse momentum. A signal consistent with several of the theoretical expectations is detected in all four data sets. We compare our results to the predictions of existing event generators and discuss in detail possible contributions from other effects that are not related to P violation.

Role of five-quark components in radiative and strong decays of the Lambda(1405) resonance

Within an extended chiral constituent quark model, the three- and five-quark structure of the S-01 resonance Lambda(1405) is investigated. Helicity amplitudes for electromagnetic decays [Lambda(1405)->Lambda(1116)gamma, Sigma(1194)gamma] and transition amplitudes for strong decays [Lambda(1405)->Sigma(1194)pi, K- p] are derived, as well as the relevant decay widths. The experimental value for the strong decay width, Gamma(Lambda(1405)->(Sigma pi)degrees) = 50 +/- 2MeV, is well reproduced with about 50% of a five-quark admixture in the Lambda(1405). Important effects owing to the configuration mixing among Lambda P-2(1)A, Lambda P-2(8)M, and Lambda P-4(8)M are found. In addition, transitions between the three- and the five-quark components in the baryons turn out to be significant in both radiative and strong decays of the Lambda(1405) resonance.

Relativistic photoionization cross sections for atomic Mg

The photoionization cross sections of the ground level (3s(2) S-1(0)) of atomic Mg have been studied theoretically in the energy region between the Mg+(3s) and Mg+(3p) threshold using the fully relativistic R-matrix method. The positions and widths of resonances have also been obtained and compared with a recent experiment (Wehlitz et al 2007 J. Phys. B 40 2385). Excellent agreement is shown between our theoretical calculations and experimental measurements. In the present calculations, five Rydberg series of doubly excited states have been exhibited, i.e. 3pns P-1, 3pnd P-1, 3pns P-3, 3pnd D-3 and 3pnd P-3, where 3pnd P-3 are confirmed as the fifth series in contrast to the previous theoretical results.

Relativistic Continuum Random Phase Approximation and Applications II. Applications

The fully consistent relativistic continuum random phase approximation (RCRPA) has been constructed in the momentum representation in the first part of this paper. In this part we describe the numerical details for solving the Bethe-Salpeter equation. The numerical results are checked by the inverse energy weighted sum rules in the isoscalar giant monopole resonance, which are obtained from the constraint relativistic mean field theory and also calculated with the integration of the RCRPA strengths. Good agreement between the misachieved. We study the effects of the self-consistency violation, particularly the currents and Coulomb interaction to various collective multipole excitations. Using the fully consistent RCRPA method, we investigate the properties of isoscalar and isovector collective multipole excitations for some stable and exotic from light to heavy nuclei. The properties of the resonances, such as the centroid energies and strength distributions are compared with the experimental data as well as with results calculated in other models.

PROBING THE SYMMETRY ENERGY AT SUPRA-SATURATION DENSITIES FROM PION EMISSION IN HEAVY-ION COLLISIONS

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6, Ska and SIII, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2.

CHARMED BARYON IN A STRING MODEL

Charmed baryon spectroscopy has been studied under a string model. In this model, charmed baryons are composed of a diquark and a charm quark which are connected by a constant tension. In this diquark picture, the quantum numbers J(P) of confirmed baryons have been well assigned. Energies of the first and second orbital excitations have been predicted and compared with the experimental data. Meanwhile, diquark masses have been extracted in the background of charm quark which satisfy a splitting relation based on spin-spin interaction.

原子核巨共振温度变化机制

我们利用流体动力学宏观理论与HF微观理论对同位旋标量多极巨共振能量随温度的变化机制做了讨论。首先用流体动力学方法导出了同位旋标量多极巨共振能量随温度变化的一般关系式。公式表明巨共振能量随温度的变化受制于热核体积膨胀和核子平均动能增加两个因素之间的竟争，它们分别使共振能减小和增加。接着又用Skyrme-HF方法得到了核半径系数和核子平均动能随温度变化的关系式。最后得到同位旋标量多极巨共振能量随温度变化的一个简单关系式。体积膨胀和核子平均动能增加这两种因素的影响大体互相抵消，最终导致热核同位旋标量多极巨共振能量基本不随温度变化。我们用Boltzmann-Nordherin-Vlasov方程数值计算和分析了重离子反应中单极巨共振OMR的形成与衰减。为了系统地比较入射能、碰撞参数对不同反应系统GMR的形成与衰减的影响，我们计算了不同条件下不同重离子反应系统的四极矩、动能和单极矩随时间的演化。计算表明，1)GMR能量与入射能和碰撞参数无关，仅仅是核子数的函数。2) 入射能愈大GMR形成稍有提前，GMR振幅也越大但OMR振幅衰减越快GMR消亡越早。3) 碰撞参数越大GMR振幅越小GMR消亡越早。4) GMR在40fm/c左右形成，依照入射能和碰撞参数的不同在200到400fm/c后消亡，入射能愈大或碰撞参数愈大GMR消亡越早。概括地讲，GMR能量是核子数的光滑函数，与入射能或激发能无关；入射能越大GMR振幅越大，GMR形成时间稍早但衰减和消亡更快。我们用经典唯象输运模型和量子输运模型讨论了核系统扩张过程中OQR模式的密度涨落并用它们来模拟系统的集体行为。我们讨论了集体坐标Q与集体动量P的涨落随时间的演化。计算显示集体变量Q的涨落发展主要取决于通过随机驱动力引入的初始统计涨落，统计涨落与量子涨落行为相似。在核系统扩张阶段耗散与涨落机制对于动量分布的影响是重要的。量子涨落在初值中已经存在，对于低温系统，量子涨落所起的作用尤为重要，它能够缩短涨落达到特定值的临界时间，从而在动力学对称性破缺中发挥重要作用。由于量子涨落的作用，处于spinodal状态的核系统将更早地分解。我们也讨论了双核系统GDR的形成与性质，还探讨了GDR宽度随温度变化的机制。

中能重离子碰撞中的同位旋效应和热核巨共振中的有限力程研究

本论文包括两部分内容，第一部分是关于中能重离子碰撞中的同位旋效应研究。第二部分是热原子核巨共振中有限力程研究。随着放射性次级核束的产生和利用，使得中能重离子碰撞中的同位旋效应研究成为核物理学的重要前沿课题。通过从稳定线到滴线附近大跨度同位旋范围内的重离子反应，使得人们可以提取核物质状态方程和介质中核子－核子碰撞同位旋旋相关截面的知识。我们将量子分子动力学(QMD)改造成为同位旋相关的量子分子动力学(IQMD)，对中能重离子碰撞中同位旋效应进行了深入而系统地研究。在研究丰中子和缺中子系统的多重碎裂过程中，发现了多重碎裂过程的同位旋效应，例如缺中子系统的中等质量碎片多重性大于丰中子系统。这对于了解多重碎裂的机理有重要意义。在研究对同位旋相关的核物质状态方程(对称势)和介质中核子－核子碰撞截面灵敏的观测量过程中，发现前平衡发射中子－质子比在较宽能区内(E<150MeV／u)对同位旋相关的核物质状态方程灵敏，但对介质中同位旋相关的核子-核子碰撞截面不灵敏；而原子核阻止在中能区(费米能

Theoretical study on the mechanism of the reaction of CH4+MgO

The reactions of (1) CH4 + MgO --> MgOH. + CH3. and (2) CH4 + MgO --> Mg + CH3OH have been studied on the singlet spin state potential energy surface at the MP2/6-311+G(2d,2p) level. These two reaction channels, both involving intermediates and transition states, have been rationalized by the structures of the species involved, natural bond orbital (NBO), and vibrational frequency analysis. We have considered two initial interacting models between CH4 and MgO: a collinear C-H approach to the O end of the MgO forming the MgOCH4 complex with C-3nu symmetry and three hydrogen atoms of the methane point to the Mg end of the MgO forming the OMgCH4 complex with C-1 symmetry. The calculations predict that reactions 1 and 2 are exothermic by 39.8 and 86.5 kJ mol(-1), respectively. Also, the former reaction proceeds more easily than the latter, and the complex HOMgCH3 is energetically preferred in the reaction of MgO + CH4.

基于进化计算的航天器轨道机动优化方法

轨道机动是航天器执行空间任务的基础，对轨道机动进行优化设计非常重要。 近年来，小推力发动机技术不断成熟，由于小推力发动机具有高比冲、低成本的优点，逐渐被用于轨道机动系统中。小推力轨道机动与常规轨道机动的不同在于小推力情况下，航天器变轨时间长，推力作用时间长，这使小推力轨道机动的优化设计极为困难。因此，小推力轨道机动优化成为航天器轨道机动优化领域的难点和热点，吸引了大批学者的关注和研究。本文对基于进化算法的小推力轨道转移时间-能量优化方法进行了研究。 由于进化算法属于一种参数优化方法，不能直接用于求解泛函形式表示的轨道转移优化问题。因此，本文引入并改进了一种基于Lyapunov反馈控制律的小推力转移轨道设计方法，使用该方法将小推力轨道转移最优控制问题转换成适合进化算法求解的多目标优化问题。 为了求解转换后的多目标优化问题，提出了一种 支配混合多目标进化算法。该算法使用基于 支配概念的选择算子，在保持群体多样性的同时，避免了许多多目标进化算法存在的退化现象。同时，为了改进算法局部搜索能力，将局部搜索方法与算法结合，构造出串行混合算法结构。 数值实验证明，本文提出的方法能够有效求解小推力轨道转移时间-能量优化问题。

Red-Light-Emitting Iridium Complexes with Hole-Transporting 9-Arylcarbazole Moieties for Electrophosphorescence Efficiency/ Color Purity Trade-off Optimization

The synthesis, structures, photophysics, electrochemistry and electrophosphorescent properties of new red phosphorescent cyclometalated iridium(III) isoquinoline complexes, bearing 9-arylcarbazolyl chromophores, are reported. The functional properties of these red phosphors correlate well with the results of density functional theory calculations. The highest occupied molecular orbital levels of these complexes are raised by the integration of a carbazole unit to the iridium isoquinoline core so that the hole-transporting ability is improved in the resulting complexes relative to those with I-phenylisoquinoline ligands. All of the complexes are highly thermally stable and emit an intense red light at room temperature with relatively short lifetimes that are beneficial for highly efficient organic light-emitting diodes (OLEDs).

Length dependence of electron conduction for oligo(1,4-phenylene ethynylene)s: A conductive probe-atomic force microscopy investigation

The dependence of electron conduction of oligo(1,4-phenylene ethynylene)s (OPEs) on length, terminal group, and main chain structure was examined by conductive probe-atomic force microscopy (CP-AFM) via a metal substrate-molecular wire monolayer-conductive probe junction. The electron transport in the molecular junction was a highest occupied molecule orbital (HOMO)-mediated process following a coherent, non-resonant tunneling mechanism represented by the Simmons equation.

Novel Re(I) dendrimers: synthesis, characterization and theoretical studies

Four novel diimine rhenium(I) carbonyl complexes with the formula [Re(CO)(3)(L) Br], where L = 2-(4-(9H-carbazol-9-yl) phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (P1), 2-(4-(3,6-di-tert-butyl-9H-carbazol-9-yl) phenyl)-1H-imidazo-[4,5-f][1,10] phenanthroline (P2), 2-(4-(6-(9H-carbazol-9-yl)-9H-3,9'-bicarbazol-9-yl) phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (D1), and 2-(4-(3', 6'-di-tert-butyl-6-(3,6-di-tert-butyl-9H-carbazol-9-yl)-9H-3,9'-bicarbazol-9-yl) phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (D2), have been successfully synthesized and fully characterized by (HNMR)-H-1, IR, and UV-Vis, etc. The luminescence quantum yields (LQYs) of the parent Re(I) complexes P1 and P2 are 0.13 and 0.16, respectively, which are much higher than the previously reported Re(I) dendrimers. The HOMOs and the LUMOs of P1 and P2 are calculated to be mainly composed of [d(Re) + pi(CO + Br)] and pi*(L) orbital, respectively.

Near compensated half-metal in Sr2NiOsO6

The electronic and magnetic properties of tetragonal double perovskite Sr2NiOsO6 were studied by use of the density functional theory and including the spin-orbit coupling. Compensated half-metal is found if the spin-orbit coupling is not considered. Spin-orbit coupling induces orbital moments on both Ni and Os, making Sr2NiOsO6 a near compensated half-metal. Ferromagnetic phase is slightly favored over antiferromagnetic phase (by 4 meV). The small energy difference also suggests that both phases are competitive for the ground state. At ferromagnetic phase, the calculated net magnetic moment is 3.53 mu(B), in good agreement with experimental value of 3.44 mu(B). At antiferromagnetic phase, the net magnetic moment is 0.69 mu(B), in which the contribution from the net spin moment is 0.09 mu(B).