Triple α-particle resonances in the decay of hot nuclear systems

The Efimov(Thomas) trimers in excited ~(12) C nuclei, for which no observation exists yet, are discussed by means of analyzing the experimental data of ~(70(64))Zn(~(64) Ni) + ~(70(64))Zn(~(64) Ni) reactions at the beam energy of E/A = 35 MeV/nucleon. In heavy ion collisions, a-particles interact with each other and can form complex systems such as ~8 Be and ~(12) C. For the 3 a-particle systems,multi-resonance processes give rise to excited levels of ~(12) C. The interaction between any two of the 3 a-particles provides events with one, two or three ~8 Be. Their interfering levels are clearly seen in the minimum relative energy distributions. Events with the three a-particle relative energies consistent with the ground state of ~8 Be are observed with the decrease of the instrumental error for the reconstructed 7.458 MeV excitation level in ~(12) C, which was suggested as the Efimov(Thomas) state.     

23Al及其邻近丰质子核的奇异结构研究

在RIKEN-RIPS上测量了²³Al等丰质子核素的核反应总截面(σ_R)和平行动量分布(P^//). 观察到了²³Al核反应总截面的增强, 与以前的实验结果相符. 同时得到了²³Al等丰质子核素擦掉一个质子后的P_//. 在Few-body Glauber模型下对实验结果进行了讨论. P_//的宽度显示²³Al基态的外层质子处于d态, 这与g因子测量实验结果一致. 为了同时解释P_//和σ_R的实验测量结果, 我们认为²³Al可能有核芯增大的现象.     

核子发射数的数学模拟:扩展BUU模型

本文在原来BUU方法的基础上,辨认了靶核与炮弹中的中、质子,同时在模拟核子的初始分布中考虑了小液滴模型修正,引入了表面弥散度、中子皮和形变参数等,使核子的分布更真实,这对丰中子、丰质子核反应以及非对称核反应尤为重要.考虑到中能核反应时,自由核子-核截面中,不同核子间的散射截面大约是同类核子间散射截面的三倍的事实,在BUU碰撞项中体现了这一点,这样可合理地取出不同核子-核子间碰撞流的问题.我们在利用这个扩展的BUU模型研究44Mev/A Kr+Au反应之前,有效地检验了模型的稳定性问题,并在文中合理地定义了核子发射的条件,得到了反应过程中弹核擦碎的中子、质子数与碰撞参数的关系以及类弹靶的关联.     

中能重离子反应中的在平面流和椭圆流

利用同位旋相关的量子分子动力学模型研究了⁴⁰Ca+⁴⁰Ca系统在能量从30MeV/u到150MeV/u的在平面流和椭圆流.发现随着入射能量的增加,在平面流出现从负到正的跃迁,而椭圆流则随入射能量的增大而减少并且出现从正到负的跃迁.椭圆流和在平面流对于入射能量和碰撞参数较为敏感,相反对于对称能和核态方程却不太敏感.最后对于不同质量的碎块的依赖性关系我们还作了进一步仔细的研究.     

CO_2激光辐照石墨产生的碳纳米结构

用高分辨透射电子显微镜（HRTEM）检查连续波CO_2激光束（波长10.6 μm, 功率300 W）辐照石墨后发现,不但有通常所见的碳纳米多面体（polyhedrons), 纳米洋葱（onions)和纳米管,而且也罕见的腔内充填大小不等空心洋葱（hollow onions, HOs）的碳纳米袋（nano-bags)。同时,在纳米袋中一些结构相似的碳 HO聚生成为HO团簇。根据这些团簇的排布情况,我们认为这种聚生物有可能是HO结 晶晶格生长的前体（precursor)。     

离子辐照与碳纳米结构体的合成

阐述了在离子辐照下生成各种碳纳米结构体研究的发展现状,探讨了相应的生长机制和一些相变机理 ,提出了一些有待解决的问题 ,并对其发展方向作了展望. The synthesis of carbon nanostructures, such as fullerenes, nanotubes, onions and diamond, by using ion irradiation, has been reviewed and the growth mechanisms of these carbon nanostructures as well as their phase transitions are simply discussed. It shows that high density plasma engendered by ion irradiation plays an important role in the growing of carbon nanostructures. In addition, it indicates that ion irradiation, due to its great flexibility of experimental parameters, is enormously convenient in...     

F同位素的反应总截面测量和17F可能的质子皮结构

应用透射法对中能区F同位素与C靶的反应总截面进行了测量。发现^17F的反应总截面比其邻近同位素的反应总截面稍有增强。用Glauber模型和BUU模型对F同位素进行了差异因子d的分析。^17F的差异因子d比共附近同位素稍有增强。分析结果表明^17F可能存在质子皮结构。     

中子皮厚度测量探针对核物质状态方程的依赖性

利用同位旋相关的量子分子动力学模型模拟了 4He + 208 Pb的碰撞反应,发现中子质子产额比与 208 Pb的中子皮之间存在很好的线性关联,中子质子产额比可以作为中子皮厚度测量的一个探针。选取量子分子动力学模型中核物质状态方程的两套不同势参数进行模拟,通过对比发现,中子皮的厚度测量探针中子质子产额比对核物质状态方程中选择软势和硬势非常敏感,相同反应条件下,软势比硬势计算所得的中子质子产额比要低。无论选择何种状态方程参数,中子质子产额比与中子皮之间都存在线性关联。The reaction system of 4He + 208Pb has been simulated by Isospin-dependent Quantum Molecu-lar Dynamics (IQMD) mode and it was found that the neutron-to-proton yield ratio (Rnp) has a good linearrelationship with the neutron skin thickness of 208Pb. Therefore Rnp could be taken as a probe of neutron skin thickness of 208Pb. Using two sets of parameters for the nuclear equation of state (EOS) in IQMD model, it shows that Rnp is sensitive to nuclear equation of state. The calculation results of Rnp with the soft EOS is lower than the hard EOS. No matter which kind of EOS parameter has been chosen, however, Rnp holds a good linear correlation with the neutron skin thickness.     

Isoscaling behavior studied by HIPSE model

The isoscaling behavior in the reaction system of 58,64Ni + 9Be has been studied by using the heavy-ion phase-space exploration(HIPSE) model. The extracted isoscaling parameters α and β for both heavy and light fragments for HIPSE model calculations are in good agreement with recent experimental data. The investigation shows that the parameters in the HIPSE model have some effect on the isoscaling parameter. The isoscaling parameters for hot and cold fragments have been extracted.     

Scaling property in one-nucleon removal reactions induced by exotic nuclei

Assuming a core plus valence nucleon structure, one-nucleon removal reaction is investigated within the framework of few-body Glauber theory. Fermi-type distribution is used for the core density, while the wavefunction of the valence nucleon is calculated by solving the single particle eigenvalue problem of the SchrSdinger equation with the Woods-Saxon potential. The parallel momentum distribution （P//） of the fragments is calculated for isotopes with 3 〈 Z 〈 18. A remarkable scaling property is observed from the dependence of the dimensionless quantity P^2 v/R^2 e on the full width at half maximum of the parallel momentum distribution （FWHMp//）. R^2 v/R^2 c is a measure of the exotic extent of the nuclear halo. Based on the obtained 2 2 scaling law, FWHMp// can be used as an experimental observable to extract R^2 v/R^2 c and measure the exotic extent for the nuclear halo.