波包宽度对弹核碎裂反应截面的影响

运用改进的量子分子动力学(ImQMD)模型嫁接GEMINI统计衰变模型对波包宽度与弹核碎裂反应截面之间的关系进行了理论分析,分析了不同的波包宽度对400 AMeV 36Ar+C,20Ne与C,Al,Cu,Sn弹核碎裂反应截面的影响,分析了同位素36Ar,40Ar与Al反应在不同的波包宽度下的同位素分布。分析结果表明:波包宽度的选择影响着弹核碎裂的反应截面,并且与核反应体系有关。当σ2_r = 2 fm2时的计算结果与实验结果一致;而σ_r =(0.88+0.09 A1/3) fm的计算结果与体系有很大的关系,对弹核碎裂的反应截面影响明显。不的波包宽度对丰中子核40Ar的弹核碎裂反应截面的影响要小于对36Ar的弹核碎裂反应截面的影响,而且随体系分布的波包宽度计算的同位素要比σ2_r =2 fm2时计算的同位素多。The relations between wave packet width and projectile fragmentation cross sections are studied in theory by using the improved quantum molecular dynamics (ImQMD) and GEMINI models. The effect of different wave packet width for projectile fragmentation cross sections is analyzed for the reaction 36Ar on C, 20Ne on C, Al, Cu, Sn at 400 AMeV, the isotope distributions with different wave packet width are studied for reactions 36Ar, 40Ar on Al. The results show that the projectile fragmentation cross sections are affected by the choice of the wave packet width, and are related to the system of nuclear reaction. The calculation results of σ2_r =2 fm2are in agreement with the experimental results, but the results of σ_r = (0.88+0.09A1/3) fm have a strong relation with reaction system and the projectile fragmentation cross sections are affected obviously. The influence of wave packet width for 40Ar projectile fragmentation cross sections is smaller than that for 36Ar.Moreover isotope distributions with system-size-dependent wave packet width are larger than with σ2_r =2 fm2.     

The fragmentation of 20Ne at 400 A MeV

The total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV ²⁰Ne with aluminum, carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors. The measured total charge-changing cross sections are compared with the predictions using the Bradt-Peters semi-empirical formula, and the NUCFRAG2 and PHITS models. It is shown that the measured experimental results are in good agreement with the theoretical model prediction and other experimental results, and it can be clearly seen that the partial cross sections for fragment production show obvious odd-even effects.     

500 AMeV 56Fe诱发乳胶核反应弹核碎裂研究

通过利用日本放射线医学综合研究所( NIRS ) 重离子医用加速器( HIMAC) 产生的束流照射国产的核-4型原子核乳胶,对500 AMeV 56Fe诱发乳胶核反应粒子产生进行了研究。讨论了500 AMeV 56Fe诱发乳胶核反应弹核碎片的多重数分布,并与其他结果进行了比较。结果表明,弹核碎片平均多重数随靶核质量的增加而增加,与入射能量无关。A stack of domestic N-4 nuclear emulsion was exposed to 56Fe ions at 500 AMeV at the HIMAC of NIRS. Particle production was investigated in 56Fe-Em interactions. The multiplicity distribution of projectile fragments was given in this paper and compared with other experimental results of heavy ion induced nuclear reactions in nuclear emulsion. The results show that the multiplicity of projectile fragments increase with the increasing target mass, and thereis no dependence on the projectile energy.     

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.     

Fragmentation of stable and neutron-rich 12-16C into boron fragments at approximately 240 MeV/nucleon

The elemental fragmentation cross sections of boron fragments produced by stable and neutron-rich^12-16C beams with a carbon target were systematically measured at an incident beam energy of approximately 240 MeV/nucleon.The measured cross sections were found to increase as the projectile mass number increases.The observed feature is explained qualitatively based on the abrasion-ablation two-stage reaction model and is compared quantitatively with predictions from various reaction models,including empirical and statistical models.All models agree with the measured cross sections within a factor of 2.     

Production of helium projectile fragments in {16O－emulsion interactions at 4.5 A GeV/c

The measurements of partial production cross sections of the multiple helium projectile fragments emitted at 4.5 A GeV/c {}^{16}O－Em interactions are reported. We have studied the production rate of helium projectile fragments due to fragmentation of {}^{16}O ions and compared it with that obtained from different projectiles at various energies. The dependence of on the mass number of the incident beams is formulated. The multiplicity distributions of the helium fragments produced in {}^{16}O－Em interactions at different energies exhibit Koba－Nielson－Olesen (KNO) scaling. The correlation of helium projectile fragments and target fragments is also investigated and it is found that the average of target fragments is increased with the decrease of the number of helium fragments in peripheral interactions.     

Isospin Effects on Anisotropic Flows in Intermediate Energy Heavy Ion Collisions

Anisotropic flows per nucleon （v1/A, v2/A, v3/A and v4/A） of light fragments up to the mass number 4 as a function of transverse momentum per nucleon are studied for 55 Me V/nucleon 58Fe＋58Fe and 58 Ni＋ 58 Ni at large impact parameters by the isospin-dependent quantum molecular dynamics model. The effects of symmetry energy and nucleon-nucleon cross sections, which are both isospin-dependent on anisotropic flows, are studied in detail. In comparison of the two systems with or without symmetry potential term, the results show that the strength of flows is sensitive to symmetry potential and nucleon-nucleon cross sections, which mainly cause a repulsion effect in this energy region.     

核子-核子碰撞截面的参数化公式

核子-核子碰撞截面(σ_NN)是描述原子核反应模型中的重要物理量。 核子-核子碰撞截面包括质子-质子碰撞截面（σ_pp）、中子-中子碰撞截面（σ_NN）和中子 质子碰撞截面（σ_np）, 它们随着核子能量与核物质密度的改变而变化。人们在目前研究中提出了多种核子-核子碰撞截面关于能量和核物质密度的参数化公式,通过计算12C+12C的完全反应截面,比较了不同入射能量下使用各种核子-核子碰撞截面参数化公式对12C完全反应截面的影响。 The nucleus-nucleus cross sections(σ_NN) include the proton-proton cross section, neutron-neutron cross section, and neutron-proton cross section. σ_NN change with the variations of the incident energies and the densities. Some parameterizations of σ_NNas a function of incident energy and density have been proposed in the theoretical and experimental study of nuclear reactions. Through the calculation of reaction cross sections of 12C+12C at different energies, the effect of different σ_NN parameterizations in the reaction cross sections of 12 are studied.      

原子核的大质量转移反应和丰中子超重核的产生(英文)

迄今为止,人们合成的超重核都是缺中子的,无论是熔合-裂变反应还是碎化过程都无法使产物达到周期表的“东北区域”。而重核之间(如U核之间) 的近垒大质量转移反应则可能是目前生成丰中子超重核和达到未知丰中子重核区域的唯一途径。在改进的量子分子动力学(ImQMD) 模型结合统计模型框架内,研究了U+U等反应体系的大质量转移反应,计算了反应产生的初生态碎片的质量和电荷分布,并成功再现了产物的终态质量和电荷分布。通过比较3 个反应136Xe+248Cm,48Ca+248Cm和238U+248Cm 产生的106号元素的截面大小,揭示了U+U等重核大质量转移反应对产生丰中子超重核是非常有利的。For elements with Z > 100 only neutron deficient isotopes have been synthesized so far. The “northeast area” of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes.The large mass transfer reactions in near barrier collisions of heavy (U-like) ions seem to be the only reaction mechanism allowing us to produce neutron rich heavy nuclei including those located at the superheavy(SH) island of stability and unexplored area of heavy neutron-rich nuclides. This study is extremely important for nuclear astrophysical investigations and, in particular, for the understanding of the r process. In this paper within the Improved Quantum Molecular Dynamics (ImQMD) model combining with the statistical-evaporation model, the large mass transfer reactions, like 238U+238U have been studied. The charge and mass distributions of transiently formed primary fragments are investigated within the ImQMD model and de-excitation processes of those primary fragments are described by the statistical decay model. The mass distribution of the final products in 238U+238U collisions is obtained and compared with the recent experimental data. Through compared the formation cross sections of transfermium element 106 by three reactions of 136Xe+248Cm, 48Ca+248Cm and 238U+248Cm, it is explored that the large mass transfer reactions, like U+U are very benefit for the production of SH nuclei.     

熔合反应中入射道质量不对成度效应

The symmetric and asymmetric fusion reaction systems forming the same compound nuclei ^26Al, ^30Si, ^38Ar and ^170Hf are investigated with the frame of improved isospin dependent quantum molecular dynamics model. The entrance channel mass asymmetry dependence of compound nucleus formation is found by analyzing the shell correction energies, the Coulomb barriers and the fusion cross sections. The calculated fusion cross sections agree quantitatively with the experimental data. The results indicate that compound nucleus formation is favorable for the systems with larger mass asymmetry because of the smaller Coulomb contribution to the fusion barrier.     

中高能重离子诱发乳胶核反应慢粒子产生(英文)

对150 AMeV 4He,290 AMeV 12C,400 AMeV 12C,400 AMeV 20Ne及500 AMeV 56Fe诱发乳胶不同靶核反应靶核碎片多重数分布及关联进行了研究。结果表明,黑径迹粒子、灰径迹粒子及重电离粒子平均多重数随靶核大小的增加而增加,不同靶核碎片多重数之间存在线性关联。这些实验结果均可以依据核-核碰撞几何模型及级联蒸发模型来解释。     

17F + p 厚靶实验对18Ne共振态性质的研究

实验通过17F+p共振弹性散射研究了复合核18Ne激发态中与天体核反应14O(α, p)17F相关的共振态性质。利用兰州放射性束流线(RIBLL)对弹核碎裂反应产生的放射性束17F进行了分离和提纯。经过降能后,能量为4.22 AMeV 的17F束流轰击在T2终端的厚氢靶(CH₂)_n上。　两套∆E-E Si探测器望远镜放置在两个不同的探测角度θ_lab≈2.3°和14°上,对反冲质子的角度和能量进行了测量。实验观测到了复合核18Ne的几条质子共振能级。通过R-Matrix理论程序对激发函数进行拟合,得到了共振态的能量、 自旋、 宇称和衰变宽度等共振参数。Resonant properties in18Ne relevant to the stellar reaction of 14O(α, p)17F have been investigated through a resonant elastic scattering of 17F+p. The 17F RI beam was produced via a projectile fragmentation reaction, and subsequently separated and purified by Radioactive Ion beam Line in Lanzhou(RIBLL). After a series of energy degradation,a 4.22 AMeV 17F beam bombarded a thick(CH₂)_ntarget at T2 terminal. Energy and angle of the recoiled protons were measured by two sets of ∆E-E silicon telescope at θ_lab≈2.3°,14° respectively. Several resonances in 18Ne were observed,and their resonant parametersincluding energy,spin parity and decay width have been determined by an R-Matrix analysis of the experimental excitation function.     

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.     

135MeV/u 12C和铁相互作用中靶余核的质量分布

用核化学技术测定了135MeV/u ¹²C和铁相互作用中的靶余核的生成截面,通过高斯电荷分布函数得到了靶余核的质量分布.与46MeV/u ¹²C+Cu相比,发现A<30质量区的产额明显增加,且产物有偏向丰中子一侧的趋势.实验测定的质量分布与熔合碎裂模型和级联两体模型的计算结果进行了比较,结果似乎表明在很高入射能情况下多重碎裂衰变是A<30靶余核生成的主要反应机制.     

xF (or y)-Dependence of Nuclear Absorption and Energy Loss Effects onJ/ψ Production

By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the J/ψ ``normal nuclear absorption' and energy loss effects are studied in a Glauber formalism at HERA and RHIC energies. Assuming that the absorption cross section σ_abs increases with thecharmonium-nucleon center of mass energy, the results reveal a significant dependence of the σ_abs on rapidity y at RHIC energies. The initial-state energy loss effect, which is found important only at HERA energies, is also considered, and its influence should be eliminated when we studied the absorption effect at low collision energies. Finally, we also present the theoretical prediction for LHC.     

Symmetric and asymmetric fission modes in proton-induced fission at 660 MeV of <Superscript>238</Superscript>U

Fission product cross sections of intermediate-energy fission of ²³⁸U were used in order to construct the charge and mass yield distributions. Enriched target of ²³⁸U was irradiated by proton beam with energy 660 MeV for several hours at the LNP Phasotron, Joint Institute for Nuclear Research (JINR), Dubna, Russia. The charge distribution of the fission fragments was analyzed for calculation of isobaric cross sections. The mass yield curves were expanded into symmetric and asymmetric components according multimodal fission approach. The fissility values of actinides were calculated at given proton energy. The obtained results have been compared to the same data for targets ²³⁷Np and ²⁴¹Am.     

温度对二氧化硫紫外吸收特性的影响

以氘灯为激发源,获得了不同温度、大气压条件下SO₂分子在285.0～320.0 nm波长区间的吸收谱。光谱图由弥散谱叠加分离谱组成,弥散谱产生于SO₂分子由基态向密集的高振转能级的吸收跃迁,分离谱主要产生于B1B₁←X1A₁跃迁,由分离谱带的间隔,获得了B1B₁激发电子态的对称拉伸和弯曲振动频率分别为：ω₁=(665±29) cm-1,ω₂=(448±17) cm-1。通过观测不同温度下的吸收谱,发现不同温度下吸收谱的结构基本相同,但吸收截面随温度升高而下降,不同吸收峰对应的吸收截面随温度呈现三次方规律变化,但比例系数不同。所以,在以吸收截面为基础的SO₂差分吸收光谱探测中,必须考虑温度变化对测量结果的影响。