重离子核反应中丰中子余核产额的标度规律

在重离子碰撞（HICs）的实验数据和动力学模拟的反应中发现了丰中子余核产额的标度现象。在这种标度现象中,两个同位旋不同的炮弹碎裂反应产生的余核中,不同中子丰度差的余核的信息熵不确定度的差具有一致的分布。利用反对称化分子动力学模型（AMD）模拟并联合退激发模型（GEMINI）模拟了140 AMeV 58,64Ni+9Be碰撞体系中余核的产额,并展示了实验测量的余核已经理论模拟得到的余核的标度现象。由于信息熵方法对反应系统是否处于平衡状态没有要求,不仅可以用于处于平衡态系统的核物质研究,也可以用于动力学变化过程中的核物质性质研究。信息熵方法将为HICs中的核物质演化研究提供新的理论分析方法。A scaling phenomena has been discovered for fragments produced in heavy-ion collisions both in the measured experiments and in the simulated reactions by transport model. In this scaling phenomena, the information entropy uncertainty difference between isobars with different neutron-excess has a uniform distribution between two reactions. The simulated reactions of 140 AMeV 58,64Ni+9Be by using the asymmetric molecular dynamics(AMD) model plus the sequential decay code GEMINI are analyzed to show the scaling phenomena of fragments. Since the application of information entropy theory does not require the system to be in equilibrium, it can be used both in the analysis of transport model and thermodynamics models. The advantage of the information entropy theory provides a new method to study the dynamical evolution of nuclear matter inheavy-ion collisions.     

中能重离子反应中对称势对熵的影响

基于同位旋相关的量子分子动力学模型,研究了对称势、束流能量、对称能强度系数对中能重离子碰撞反应系统的熵的影响。研究发现,对称势对熵有一定影响,且对熵的影响大小与反应系统中质比有关。另外发现在40Ca+40Ca和40Si+40Si反应系统中对称能强度系数对熵也有影响,当对称能强度系数c=32 MeV时,对这两个系统来说其对熵的影响最大。通过实验上对熵的测量可以得到对称势的形式和大小。Based on the isospin-dependent quantum molecular dynamics model,effects of the symmetry potential,incident beam energy and different symmetry energy strength coefficients on the entropy of reaction system are studied.The results show that the symmetry potential affects the entropy,and the effect changes with the neutron-proton ratio of the reaction system.Besides,in 40Ca+40Ca and 40Si+40Sireaction systems,the symmetry energy strength coefficient also has effect on the entropy when the symmetry energy strength coefficient c=32 MeV,the effect on the entropy is largest for the two systems.Therefore the form and size of symmetry potential could be obtained by comparison of the model calculation and the experiments on the measurement of entropy.     

核结构模型中的两体以上相互作用（英文）

讨论了核结构模型中两体以上相互作用的可能形式。首先以基于手征微扰论并适于描述轻核的三体接触型相互作用为例,讨论了能合理描述3H 和3He 结合能的三核子接触型相互作用相关的两个低能有效耦合参数c_D 和c_E间的关系并通过4He 结合能给出了相应的物理参数区。其次通过Okubo-Lee-Suzuzki 有效相互作用方法对核多体问题在有限模型空间的求解,论证了A-体相互作用项。最后利用包含了A-体推广对力的可解模型对重核的同位素长链进行了分析。以132Sn 为核芯,通过对Sn 同位素链的计算揭示了推广对力参数G（A） 与模型价核子空间维数dim（A） 间的显著关系:G（A）=259.436 dim（A）-0.9985。这些分析结果说明,有必要对核中经手征微扰论或其它唯象理论所得到的NNN-,NNNN-,及A-体相互作用作进一步的研究。We discuss modeling of nuclear structure beyond the 2-body interaction paradigm. Our first example is related to the need of three nucleon contact interaction terms suggested by chiral perturbation theory. The relationship of the two low-energy effective coupling parameters for the relevant three nucleon contact interaction terms c_D and c_E that reproduce the binding energy of 3H and 3He has been emphasized and the physically relevant parameter region has been ilustrated using the binding energy of 4He. Further justification of A-body interaction terms is outlined based on the Okubo-Lee-Suzuki effective interaction method used in solving the nuclear many-body problem within a finite model space. The third example we use is an exactly solvable A-body extended paring interaction applied to heavy nuclei with a long isotopic chain; in particular using 132Sn as closed core system illustrates a remarkable relationship between the extended pairing strength G(A) and the size of the valence space dim(A) for the members of the Sn-isotope chain: G(A)=αdim(A)-β with α=259.436 and β =0.9985 which is actually a one parameter expression since β is practically 1. These three cases present evidence for the need of better understanding of the NNN-, NNNN-, and A-body interactions in nuclei either derived from ChPT or from a phenomenological considerations.     

偏离朗伯比尔定律NaCl水溶液的红外光谱合成

氯化钠水溶液中,水分子之间的氢键相互作用随氯化钠浓度变化而发生改变,导致不同浓度的水溶液光谱形状也不同,因此NaCl溶液的光谱不满足朗伯比尔定律。如果浓度c与吸光率A不满足朗伯比尔定律,则利用光谱差减技术扣除溶剂水的吸收峰问题就会遇到瓶颈,差减效果不能令人满意。利用二元线性回归分析法和双边夹原理合成杂化光谱,期望在偏离朗伯比尔定律体系,可以理论上获得各种浓度的NaCl水溶液的杂化光谱,并且保证杂化光谱与其代表的真实光谱高度相似。主要结论如下：(1)浓度c₁和c₂的NaCl水溶液的红外光谱分别为A_c1和A_c2,则浓度介于c₁和c₂之间的溶液光谱,均可用A_hc(c₁, c₂)=âA_c1 +A_c2来表示。A_hc(c₁, c₂)与浓度为c(c₁＜c＜c₂)的溶液的真实光谱A_c高度类似。(2)c₂和c₁间隔越小,杂化光谱A_hc(c₁, c₂)与真实光谱A_c的相似度越高,因此可根据精度要求选择合适的A_c1和A_c2来拟合A_hc 。(3)杂化光谱A_hc(2%, 30%)=âA_2%+A_30%,适用浓度区间2%～30%,涵盖浓度范围宽,效果令人满意。(4)回归系数â和与浓度c关系为â=-3.592c+1.058 9,=3.565c-0.0551 5。在2%~30%浓度范围内,选取浓度c数值,即可获得相应回归系数â和,再将â和代入方程A_hc(2%, 30%)=âA_2%+A_30%,即可获得NaCl水溶液的杂化光谱。杂化光谱与相对应的真实光谱高度近似,A_hc(2%, 30%)≈A_c,完全可替代真实光谱。     

Collective Transverse Flow in Intermediate Energy Heavy-Ion Collisions

Within the hadronic transport model IBUU04, we study the density-dependent symmetry energy by using the neutron-proton differential flow from the 132Sn＋124Sn reactions at beam energies of 200, 400, 600 and 800MeV per nucleon. The strong effect of the symmetry energy is shown at the incident beam energy of 400MeV/A. The small medium-effect of the neutron-proton differential flow is also found. We also study the neutron-proton differential flows with impact parameters of 3, 5, 7fm. It is found that in semi-central collisions the sensitivity of the neutron-proton differential flow to the symmetry energy is larger.     

几百兆电子伏特/核子能区原子核诱发乳胶核反应靶核蒸发碎片前后发射研究（英文）

对150 AMeV 4He-AgBr,290 AMeV 12C-AgBr,400 AMeV 12C-AgBr,400 AMeV 20Ne-AgBr及500 AMeV 56Fe-AgBr作用靶核蒸发碎片在反应前后半球内的多重数分布、多重数矩、标度方差、熵及约化熵分别进行了分析。实验结果表明,靶核蒸发碎片在前后半球内的多重数分布可以用高斯分布来描述。在前后半球内的多重数分布矩分别随秩数的增加而增加,且前后半球内多重数分布二阶矩与反应类型及束流能量无关。对于所有研究的核反应,其标度方差（一个直接描述多重数涨落的变量）值接近于1,表明在前后半球内靶核蒸发的发射存在较弱的关联。在前后半球内靶核蒸发碎片发射过程中的熵及约化熵在实验误差范围内与反应系统无关。The multiplicity distribution,multiplicity moment,scaled variance,entropy and reduced entropy of target evaporated fragments emitted in forward and backward hemispheres in 150 AMeV 4He-AgBr,290 AMeV 12C-AgBr,400 AMeV 12C-AgBr,400 AMeV 20Ne-AgBr and 500 AMeV 56Fe-AgBr interactions are investigated.It is found that the multiplicity distribution of target evaporated fragments emitted in both forward and backward hemispheres can be fitted by a Gaussian distribution.The multiplicity moments of target evaporated particles emitted in the forward and backward hemispheres increase with the order of the moment q,and the second-order multiplicity moment is energy independent over the entire energy range for all the interactions in the forward and backward hemisphere.The scaled variance,a direct measure of multiplicity fluctuations,is close to one for all the interactions,which indicate a weak correlation among the target evaporated fragments.The entropy of target evaporated fragments emitted in forward and backward hemispheres are the same respectively for all of the interactions,within experimental errors.     

Disappearance of isospin effect in projectile fragmentation at intermediate energy

The 140~MeV/u ^40,48Ca+^9Be and ^58,64Ni+^9Be reactions are simulated by the statistical abrasion ablation model, and the simulation results are compared to the National Superconducting Cyclotron Laboratory (NSCL) experimental data. By comparing the fragment isotopic distributions of ^40,48Ca and ^58,64Ni, we study the isospin effect in the projectile fragmentation induced by the neutron-rich nuclei at intermediate energy experimentally and theoretically. It is found that the isospin effect in projectile fragmentation decreases and even disappears as the violence of the collision increases.     

中高能28Si碎裂截面研究进展

介绍了利用CR-39探测器对28Si与不同靶作用的电荷变化总截面和分截面的研究进展,给出723AMeV 28Si与碳靶作用电荷变化总截面和分截面的最新实验结果。对28Si与靶核反应电荷变化总截面和分截面与束流能量和靶核质量的关系进行了讨论,发现束流能量大于200 AMeV时,中高能28Si与不同靶核反应电荷变化总截面与束流能量无关,分截面表现出明显的奇偶效应,且随靶核质量数的增加而增加。In this paper, the development of the total and partial charge changing cross sections of 28Si ions beam in different targets using the CR-39 detectors are reviewed. The newest experimental results of the total and partial charge changing cross sections of 28Si in carbon target at 723 AMeV are presented. The dependence of the target mass and the cross sections of 28Si including the total and the partial charge changing cross sections are discussed. It is found that the total charge changing cross sections of 28Si are independent of the energy when the energy of the ions beam is greater than 200 AMeV. The partial charge changing cross sections show an obviously odd-even effect, and increase with the increasing of the mass number of the target.     

Impact Parameter Dependence of the Double Neutron/Proton Ratio of Nucleon Emissions in Isotopic Reaction Systems

Within the transport model IBUU04, we investigate the double neutron/proton ratio of free nucleons taken from two reaction systems using two Sn isotopes at a beam energy of 50 MeV/nucleon and with impact parameters 2fm, 4fm and 8fm, respectively. It is found that the double neutron/proton ratio from peripheral collisions is more sensitive to the density dependence of the symmetry energy than those from mid-central and central collisions.     

随机相互作用系综内的镉同位素电磁矩线性演化

在随机相互作用系综内,镉同位素11/2-同质异能态的电四极矩与磁偶极矩总是倾向于随中子数的增加呈线性演化,这与近年来的实验观测是一致的。除了对力对磁矩线性演化的决定性影响之外,特定形式的质子-中子相互作用被认为是这种线性演化的主要驱动力:电矩的线性演化要求质子中子之间的四极相互作用;磁矩则要求质子中子之间的短程相互作用,并且这种相互作用应具有与真实核相互作用一致的相对强度与正负性。In random-interaction ensembles, the electric quadrupole moments (Q) and magnetic moments (μ) of the Iπ=11/2- isomers of the Cd isotopes predominantly present linear correlation with neutron numbers, corresponding to the recently emphasized linear Q and μ systematics in realistic nuclear system. Although the seniority scheme enhances such predominance (more essentially for μ), the configuration mixing due to quadrupolelike and δ-force-like proton-neutron interactions is responsible for the linear Q and μ systematics, respectively, at least in random-interaction ensembles. Especially, the linear μ systematics further requires the proton-neutron interaction have similar relative strength and attractive-repulsive property to realistic nuclear interaction.     

张量力在16O+16O熔合动力学中的效应（英文）

利用时间相关Hartree-Fock 理论和完整Skyrme 有效相互作用研究了16O+16O 碰撞在库仑位垒附近的熔合动力学。数值计算是在没有任何对称性约束的三维笛卡尔基下完成。将时间相关Hartree-Fock 理论和冻结密度近似下的能量密度泛函方法给出的库仑位垒与实验结果进行了比较,发现同位旋标量的张量项能降低自旋饱和体系16O+16O的库仑位垒,而库仑位垒高度随着同位旋矢量的张量项的耦合常数减小而降低。并计算了包含和不包含张量力的16O+16O熔合截面,发现张量力对16O+16O碰撞在库仑位垒附近的熔合动力学影响较小。The fusion dynamics of 16O+16O around Coulomb barrier has been studied in the timedependent Hartree-Fock (TDHF) theory with the full Skyrme effective interaction. The calculations have been carried out in three-dimensional Cartesian basis without any symmetry restrictions. We have included the full tensor force and all the time-odd terms in Skyrme energy density functional (EDF). The Coulomb barrier obtained from the dynamical TDHF calculations and EDF with frozen density approximation has been compared with the available experimental data. The isoscalar tensor terms and the rearrangement of other terms are found to decrease the barrier height in the spin-saturated system 16O+16O, while the energy of Coulomb barrier tends to decrease as the isovector coupling constant decreases. The fusion cross section for 16O+16O collision has been calculated with and without the tensor force. We found that the tensor force has minor effect on the fusion dynamics of 16O+16O at the energies around Coulomb barrier.     

10Be中子谱因子的实验研究

核谱因子描述了单粒子轨道中核子的占有状态,在核结构和核天体物理中有重要的应用。目前国际上10Be中子谱因子的研究结果存在3倍左右的差异。本实验利用中国原子能科学研究院HI-13串列加速器的高灵敏度Q3D磁谱仪,对13C（9Be,10Be）12C反应角分布进行了精确测量。通过实验数据和扭曲波玻恩近似（DWBA）计算结果进行比较,导出了10Be的中子谱因子。该结果与转动不变壳模型理论及曾敏尔等的评价结果基本一致。利用该结果可以得到9Be（n,γ）10Be的天体物理反应率,评价该反应在相关天体环境中对CNO循环种子核12C的影响,为核结构和核天体物理提供可靠数据。Spectroscopic factor describes the overlap between the initial and final states and gives some information on the occupancy of a given single-particle orbiting around nuclear. It plays an important role in a variety of topics on nuclear structure and nuclear astrophysics. Nowadays, several experiments have been performed to study the neutron spectroscopic factor of 10Be, but the results have a big difference with each other. In order to clarify this discrepancy, new measurement is highly needed. In this work, the angular distribution of 13C(9Be,10Be)12C reaction was measured at the Q3D magnetic spectrometer of the HI-13 tandem accelerator, China Institute of Atomic Energy, Beijing. And then, the neutron spectroscopic factor of 10Be was derived by normalizing the calculational differential cross-sections with the distorted-wave Born approximation to the experimental data. The present value is in good agreement with that obtained by Tsang et al. and also in good agreement with that derived from translationary invariant shell model calculation. One can use this result to calculate the 9Be(n, γ)10Be reaction rates and calculate its influence to the production of 12C.     

利用18O(6Li,d)22Ne反应研究22Ne Eα=470 keV共振态的性质

慢速中子俘获过程（s过程）是合成比铁重元素的重要途径之一。22Ne（α,n）25Mg反应是大质量AGB星中s过程主要的中子源,其中的22Ne主要通过14N（α,γ）18F（β+）18O（α,γ）22Ne反应链合成。该反应链中关键反应18O（α,γ）22Ne在天体物理感兴趣能区的截面非常低,其天体反应率主要来自于22Ne α分离阈附近低能共振态的贡献,但目前相关能级的共振参数严重缺失。在HI-13串列加速器的Q3D磁谱仪上,通过测量18O（6Li,d）22Ne反应的角分布,利用DWBA分析确定了22Ne分离阈附近共振能级E_α=470 keV的自旋宇称为0+,为后续计算18O（α,γ）22Ne的天体反应率打下了基础。About a half of the abundances of elements heavier than iron comes from the so-called slowneutron capture process (s-process) in Asymptotic Giant Branch (AGB) stars, with the 22Ne(α, n)25Mg reaction as one of the main neutron sources. In the beginning phase of AGB thermal pulse, 22Ne is produced by the 14N(α, γ)18F(β+)18O(α, γ)22Ne reaction sequence, in which the 18O(α, γ)22Ne reaction plays a key role. While the reaction rate of the 18O(α, γ)22Ne is mainly affected by several resonant states lying closely to the α threshold in 22Ne, up to now, the relevant 22Ne parameters are fragmentary in the energy region corresponding to the typical temperatures of s-process. The direct measurement of the 18O(α, γ)22Ne reaction rate is extremely difficult due to the very low cross section. In this work, we investigated the 22Ne resonant states via the 18O(6Li, d)22Ne reaction at the Beijing HI-13 tandem accelerator of China Institute of Atomic Energy. Based on the DWBA analysis, preliminary results showed that the spin-parity of 22Ne E_α=470 keV resonant states was assigned as 0+, which would make contributions to subsequent calculation for the reaction rate of the 18O(α, γ)22Ne.     

氦原子2~3S—2~3P精密光谱研究

氦原子是最基本的多电子原子,其精密谱是十分理想的检验多电子量子电动力学计算的平台,同时也是利用原子能级结构测定精细结构常数α的理想体系,还能获得原子核结构信息.本文结合我们团队的工作,综述基于氦原子的少体原子精密光谱研究.其中,主要包括氦原子2~3P_J精细结构分裂,以及2~3S—2~3P跃迁频率测定等研究,并对相关工作的前景进行了展望.     

12C+13C在库仑位垒以下能区的熔合截面测量

深垒下能区的12C+13C熔合截面测量对检验天体中熔合反应外推模型具有很重要的意义。目前在库仑位垒以下能区存在的各种测量结果,都利用了统计模型来修正得到熔合截面,但对于这些方法间的系统误差仍没有很好地研究。实验采用离线活度测量的方法,在E_c.m.=4.4～5.8 MeV能区内对12C+13C熔合截面进行测量。经Hauser-Feshbach统计模型对分支比的修正后,熔合总截面由24Na活度推导出。通过本实验数据与其它实验方法获得的数据进行比较,确定了统计模型的系统误差为14%。The study of fusion reactions of 12C+13C at the deep sub-barrier energies is very important for the test of predictive power of the extrapolation models for nuclear reactions for astrophysics. Until now, all the measurements below Coulomb barrier energies have to use the statistical model calculations to estimate the branching ratios to deduce the total fusion cross sections. However, the systematic uncertainty induced by the calculated corrections has not been studied well. In this experiment, the fusion cross sections of 12C+13C have been measured using an offline activity measurement in the range of E_c.m.=4.4 to 5.8 MeV. The total fusion cross sections have been deduced from the 24Na activities after correcting the branching ratios estimated with the Hauser-Feshbach statistical model. Through the comparison between our result and other data obtained with other methods, the systematic uncertainty of statistical model has been determined to be 14%.     

恒星氦燃烧关键反应12C(α,γ)16O天体物理S因子及其反应率

恒星氦燃烧阶段3α反应和12C（α,γ）16O反应相互竞争,两者的反应率共同决定了氦燃烧结束后12C与16O的丰度比,该比值是大质量恒星后继演化以及伴随的元素核合成过程的初始条件。目前,氦燃烧12C（α,γ）16O反应起始T₉=0.2处,天体物理模型要求的反应率的精确度要低于10%,然而尚未有实验或理论给出满足要求的结果。最为直接和可靠地获取12C（α,γ）16O反应率的方法,就是尽可能往低能区测量其天体物理S因子,然后通过理论外推到感兴趣的能区。为此基于经典的R-矩阵理论,建立了适用于低能核反应的多道、多能级的约化R-矩阵理论来拟合几乎所有可用的16O系统的实验数据。配合使用协方差统计和误差传播理论,拟合外推得到了客观的、内部自恰的和唯一性好的12C（α,γ）16O反应天体物理S因子。总的外推S因子STOT（0.3 MeV）=162.7±7.3 keV·b,理论上首次给出达到恒星演化与元素核合成模型的最低要求的S因子。基于计算给出的全能区的S因子,数值积分给出了温度位于0.04 6 T₉ 6 10的12C（α,γ）16O天体物理反应率。在T₉=0.2处,推荐的反应率为（7.83 ±0.35）×10-15 cm3mol-1s-1。During stellar helium burning, the rates of 3α and the 12C(α,γ)16O reaction, in competition with one another, determine the relative abundances of 12C and 16O in a massive star. The abundance ratio is the beginning condition of the following nucleosynthesis and star evolution of massive stars, which are extremely sensitive to the rate of 12C(α,γ)16O reaction at T₉=0.2. The most direct and trustworthy way to obtain the reaction rate of the 12C(α,γ)16O reaction is to measure the S factor for that reaction to as low energy as possible, and to extrapolate to energies of astrophysical interest. Based on a new multilevel and multichannel reduced R-matrix theory for applications in nuclear astrophysics, we have obtained an accurate and self-consistent astrophysical S factor of 12C(α,γ)16O, by a global fitting for almost all available experimental data of 16O system, with the coordination of covariance statistics and error-propagation theory. The extrapolated S factor of 12C(α,γ)16O was obtained with a recommended value STOT (0.3 MeV)=162.7±7.3 keV·b. And the reaction rates of 12C(α,γ)16O for stellar temperatures between 0.04 6 T₉ 6 10 are provided. At T₉=0.2, the reaction rate is (7.83 ±0.35)×10-15 cm3mol-1s-1, where stellar helium burning occurs.     

238U（9Be,5n）242Cm熔合蒸发反应激发函数测量（英文）

第一次测量到238U（9Be,5n）242Cm熔合蒸发反应的激发函数。通过使用叠层靶,在不改变束流能量的条件下,在线获得20个能量点下的实验数据。利用蒸发余核242Cm的半衰期较长,且衰变模式是α衰变的特点,用离线测量α放射性的方法得到目标核产额。实验最大截面约1 mb,激发函数曲线的形态和峰值所在的能量位置与现有的理论模型的计算结果一致。激发函数的实验数据对选择和优化理论模型,推动超铀核区核物理研究具有重要的意义。The excitation function of the 238U(9Be, 5n) reaction was obtained for the first time. By using a stack of uranium targets, 20 experimental data were obtained by the on-line irradiation without changing beam energy. Taking the advantage of the long lifetime and α decay mode of the residue nucleus 242Cm, the off-line measurement of the α radioactive was performed to obtain its yields. The maximum cross section is about 1 mb. The curve's shape and the maximum's position agree with the present model. The value of the cross section will help us to develop the ralated models, and push the nuclear studies in the transuranium region.     

采用量子波包方法和准经典轨线方法研究S(~3P)+HD反应

利用量子波包方法和准经典轨线方法在一个新的3A′′势能面上研究了S(3P)+HD→SD+H和SH+D反应的动力学性质.计算得到了两个反应通道在碰撞能为0.8—2.2 eV范围内的J=0反应几率、积分反应截面、内同位素因子和产物转动取向因子.这些结果揭示了S(3P)+HD反应非常明显的内同位素效应.通过对势能面和反应轨线的分析,我们发现了SD+H反应通道一个新的反应机制.S(3P)+HD反应的内同位素效应可以利用新发现的反应机制和反应的质量组合来进行解释.     

Measurements of interaction cross sections and radii of He isotopes

Secondary beams of ³He, ⁴He, ⁶He, and ⁸He were produced through the projectile fragmentation of an 800 MeV/nucleon ¹¹B primary beam. Interaction cross sections (σ_I) of all He isotopes of 790 MeV/nucleon on Be, C, and Al targets were measured by a transmission-type experiment. The interaction nuclear radii of He isotopes R_I(He) = (σ_I/π)^1/2 − R _I(T) where R_I(T) is the radius of the target nucleus, have been deduced to be R_I(³He) = 1.59 ± 0.06 fm, R_I(⁴He) = 1.40 ± 0.05 fm, R_I(⁶He) = 2.21 ± 0.06 fm, and R_I(⁸He) = 2.52 ± 0.06 fm.