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.     

利用低能质子束产生高强度放射性束流

加拿大TRIUMF实验室利用¹¹C成功验证了一种产生高强度(～10⁸ions/s)放射性束流的方法. 该方法不同于普通在线同位素分离方法, 它利用了13MeV的低能强流质子束, 可以产生一系列核天体物理实验感兴趣的高强度放射性束流.     

核子碰撞截面的介质修正对多重碎裂的影响

利用同位旋相关的量子分子动力学模型研究了中能重离子碰撞过程中,同位旋相关的核子碰撞截面的介质修正对于多重碎裂的影响.结果表明:在包括动量相关作用在内的软势的情况下,介质修正明显地提高了自由核子的发射和中等质量碎片的多重性对于核子碰撞截面的同位旋依赖的敏感性.但对于原子核阻止敏感地依赖于核子碰撞截面的同位旋效应而不敏感地依赖于对称势的形式这一性质的影响并不明显,因此,原子核阻止对于核子碰撞截面的同位旋依赖的敏感性主要决定于自由核子碰撞截面的同位旋相关性.     

Probing the medium effect and isospin dependence of the in-medium nucleon--nucleon cross section in heavy ion collisions

Probing in-medium nucleon-nucleon （NN） cross section σ1/NN（α） in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics （IQMD） with the isospin- and momentum-dependent interaction （IMDI（T））. It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section α1/NN（α） in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1/NN（α） in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R＇s in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1/NN（α） because of adding a new judgement.[第一段]     

60AGeV 16 O诱发乳胶核反应α射弹碎片发射研究

对60AGeV^16O诱发乳胶核反应射弹α碎片的发射进行了研究，得到α射弹碎片多重数分布服从KNO标度无关性。在边缘作用下，α射弹碎片的产生与靶核碎片的产生存在线性关联，靶核碎片平均多重数随α射弹碎片数的增加线性减小，它可以很好地利用核作用几何模型来解释。     

60 A GeV16O原子核在核乳胶中的电磁离解

对60 A GeV¹⁶O在原子核乳胶中的电磁离解现象首次进行了高统计的研究,得到电磁离解截面随束流能量的增加而增加,射弹碎片电荷分布和200 A GeV¹⁶O在 乳胶中电磁离解的电荷分布一致,但电荷为3≤Z≤5的射弹碎片的发射概率低于200 A GeV能 区,这些特点和Weiszacker和Williams的经典电磁理论模型计算结果一致.60 A GeV¹⁶ O电磁离解下各反应道出现的概率和200 A GeV能区结果基本一致,但同14.6 关键词：电磁离解射弹碎片碎裂     

Electromagnetic dissociation of 3.7 A GeV^16O in nuclear emulsion

The electromagnetic dissociation (ED) of 3.7 A GeV {}^{16}O in nuclear emulsion is investigated with high statistics. It is found that the electromagnetically dissociated cross section increases with increasing beam energy, the charge distribution of projectile fragments is the same as the results at 60 and 200 A GeV, and the production probability of projectile fragments with charge 3≤Z≤5 is less than that of the other projectile fragments. These results can be well explained by use of Weizsacker and Williams method for calculating the ED contributions. The percentile abundance of various decay modes for ED at 3.7 A GeV is close to the result at 60 and 200 A GeV, but it is different from the result at 14.6 A GeV. The ED of 3.7 A GeV is mainly caused by the giant dipole and quadrupole resonance of E1 and E2, which can be qualitatively explained by the multiplicity distribution of projectile proton in ED. The multiplicity distribution of the α fragments in ED and nuclear events have different functional forms. This difference may be a consequence of the different reaction mechanism involved.     

Single source emission of proton projectile fragments in nucleus-emulsion interactions

The projected angular distribution and transverse momentum distribution of proton projectile fragments produced in 3.7A GeV 16O,500A MeV 56Fe,and 1.7A GeV 84Kr induced by different kinds of emulsion target(H,CNO,and AgBr) interactions are investigated.It is found that the projected angular distribution and transverse momentum distribution can be well represented by a single Gaussian distribution.Comparison of transverse momentum distribution with the Maxwell-Boltzmann distribution reveals that proton projectile fragments are emitted from a single-temperature emission source.The temperature is different for different colliding systems,and linearly depends on the target size.     

中子与56Fe反应的理论计算

应用光学模型、核内级联模型、激子模型（含改进的Iwamoto-Harada模型）、统一的Hauser-Feshbach理论以及扭曲波玻恩近似理论,对入射能量在20 MeV以下中子与56Fe非弹性散射反应的γ产生截面、分立能级截面和总的非弹性散射截面进行计算,并与最新实验数据以及来自ENDF/B-VII、JEFF-3.1和JENDL-4库的评价数据进行比较和分析。结果显示,理论计算结果与实验数据符合较好,并且对于有些激发态的非弹性散射截面我们的计算结果优于ENDF/B-VII,JEFF-3.1和JENDL-4库的评价结果。The gamma production, level production and total inelastic scattering cross sections are calculated at incident neutron energy below 20 MeV. The optical model, the intra-nuclear cascade model, the exciton model (including improved Iwamoto-Harada model), the uni ed Hauser-Feshbach theory and the distorted wave Born approximation theory are used. Theoretical calculated results are compared with the recent experimental data and other evaluated data from ENDF/B-VII, JEFF-3.1, and JENDL-4. It is found that our calculated results agree with the experimental data and the calculated results for some level cross sections are more consistent with the related experimental data than the results from ENDF/B-VII, JEFF-3.1, and JENDL-4 data base.     

60 A GeV16O原子核在核乳胶中的电磁离解

对60 A GeV16O在原子核乳胶中的电磁离解现象首次进行了高统计的研究,得到电磁离解截面随束流能量的增加而增加,射弹碎片电荷分布和200 A GeV16O在乳胶中电磁离解的电荷分布一致,但电荷为3≤Z≤5的射弹碎片的发射概率低于200 A GeV能区,这些特点和Weiszacker和Williams的经典电磁理论模型计算结果一致.60 A GeV16O电磁离解下各反应道出现的概率和200 A GeV能区结果基本一致,但同14.6 A GeV能区的结果不同,在60 A GeV能区16O电磁离解主要是由电偶及电四激发引起的巨偶极和巨四极共振及准氘核效应过程所致,这一点可以通过电磁离解下质子的多重数分布得到定性解释.电磁离解下α射弹碎片的分布同非弹核作用下α碎片的分布规律不同,说明α碎片的产生机制不同.     

Isoscaling of projectile-like fragments

In this paper, the isotopic and isotonic distributions of projectile fragmentation products have been simulated by a modified statistical abrasion--ablation model and the isoscaling behaviour of projectile-like fragments has been discussed. The isoscaling parameters α and β have been extracted respectively, for hot fragments before evaporation and cold fragments after evaporation. It looks that the evaporation has stronger effect on α than β. For cold fragments, a monotonic increase of α and β with the increase of Z and N is observed. The relation between isoscaling parameter and the change of isospin content is discussed.     

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.     

Fragmentation in ^16 O-emulsion interactions at 3.7 A GeV

The topology of ¹⁶O fragmentation at 3.7 A GeV in reactions with emulsion nuclei is presented. The multiplicity distributions of projectile fragments,charged secondaries and their dependences on the projectile residues are discussed.     

C70的吸收光谱

以甲苯为溶剂,测量了Ｃ６０和Ｃ７０混合物的紫外－可见吸收光谱;以Ｃ６０和Ｃ７０的甲苯饱和溶兴的蒸发模发膜为样品,测量了Ｃ６０和Ｃ７０混合的红外吸收光谱。经过比较确定了Ｃ７０的吸收光谱。     

C60/C70在空气中高温状态下的聚合

Ｃ６０（含Ｃ７０）固体在空气中封闭,在８５０－９００℃高温下处理１０分钟,红外光吸收光谱分析发现Ｃ６０（７０）在氮氧的作用下产生聚合。