密度分布对原子核阻止同位旋效应的影响

利用同位旋相关的量子分子动力学（IQMD）模型,分析了中能重离子碰撞过程中相对论平均场和SkyrmeHartrere－Fork等核结构模型给出的核密度分布对原子核阻止的影响。研究表明,从费米能到的较大能量范围内,无论小质量体系还是大质量体系,原子核阻止对同位旋相关的核子－核子碰撞截面都非常灵敏,而不同模型给出的核密度分布对原子核阻止影响不大,说明原子核阻止作为提取同位旋相关核子－核子碰撞截面的灵敏探针是与原子核结构模型无关的。 Influence of densitydistributionwhichisgivenbyRMFandSkyrme－Hartrere－Fork etalnuclearstructuremodelonnuclearstoppinginheavy－ioncollisionsatintermediateenergiesarestudiedbyusingisospin－dependentquantummoleculardynamics(IQMD)model.ResearchshowsthatrangeformtheFermienergytothelargerenergyof 100 Mev/u, for bothsmallandlargemasssystem,nuclearstoppingisfoundtobestronglydependentonthenucleon－nucleoncrosssections,andweaklyondifferentdensitydistribution.ThisshowsthatnuclearstoppingcanbeusedasaprobetoextracttheinformationontheisospindependenceN－Ncrosssectionsandhasnorelationshipwithnuclearstructuremodels.     

从能谱中提取核子-核子碰撞截面的信息

用同位旋相关的量子分子动力学(IQMD)模型计算了入射能量在30~200 MeV/u内, 不同中质比的反应系统(76Zn+76Zn, 76Ge+76Ge,76Se+76Se和76Kr+76Kr)碰撞产生的原子核阻止和反应产物能谱。 发现原子核阻止和不同方向的动能比值有很强的关联性,且可以用垂直方向和平行方向的碎片总动能比值的平方根近似地代替原子核阻止,用来提取同位旋相关介质中的核子-核子碰撞截面的信息。在核反应实验中,很容易测量到该物理量, 它是一个较好的探针。 The collision of different neutron/proton ratio, intermediate mass reaction systems(76Zn+76Zn, 76Ge+76Ge,76Se+76Se and 76Kr+76Kr) at the beam energy of 30~200 MeV/u are studied by using isospin dependent quantum molecular dynamics(IQMD) model. It is found that there exists a strong relationship between nuclear stopping and the ratio of different direction kinetic energy, and nuclear stopping can be replaced by the square root of the ratio of perpendicular and parallel total kinetic energy of fragments, and it can be used to extract information of isospin dependent in medium nucleon nucleon cross section. This physical quantity can be easily measured in nuclear reaction experiments, and it is a better probe.     

Study of the total reaction cross section via QMD

This paper presents a new empirical formula to calculate the average nucleon-nucleon (N-N) collision number for the total reaction cross sections (σ_R). Based on the initial average N-N collision number calculated by quantum molecular dynamics (QMD), quantum correction and Coulomb correction are taken into account within it. The average N-N collision number is calculated by this empirical formula. The total reaction cross sections are obtained within the framework of the Glauber theory. σ_R of ²³Al+¹²C, ²⁴Al+¹²C, ²⁵Al+¹²C, ²⁶Al+¹²C and ²⁷Al+¹²C are calculated in the range of low energy. We also calculate the σ_R of ²⁷Al+¹²C with different incident energies. The calculated σ_R are compared with the experimental data and the results of Glauber theory including the σ_R of both spherical nuclear and deformed nuclear. It is seen that the calculated σ_R are larger than σ_R of spherical nuclear and smaller than σ_R of deformed nuclear, whereas the results agree well with the experimental data in low-energy range.     

不同氧分压下直流反应溅射ZnO薄膜的结构和光学特性

在室温,不同氧分压条件下,采用Zn靶直流反应溅射在石英衬底上制备了具有纤锌矿结构(002)择优取向的ZnO薄膜。薄膜的生长速率随氧分压的增大而减小,在20%-30%之间存在一个拐点,在此点之前,溅射产额减小的速率很快,而在此点之后,溅射产额减小的速率减慢了很多,当氧分压在30%以上时,溅射过程中Zn的氧化在靶表面就已经完成。通过单振子模型分析了薄膜的光学特性,采用X射线衍射的方法对薄膜的晶粒尺寸和应力进行分析。研究结果表明在氧分压20%以上时,薄膜在可见光波段具有较好的光学透明性和很高的电阻率。薄膜的光学折射率、晶面间距和内部应力均随着氧分压的增大而增大。并从薄膜生长机理上给出了理论解释。