6Li与核弹性散射的微观光学势

从基本的Dirac-Brueckner-Hartree-Fock微观理论出发,得到同时包含实部和虚部的核子-核散射的微观光学势,并利用折叠模型直接获得了核一核散射参数无关的整体微观光学势.考虑到核.核散射去弹过程高级项的贡献和6Li的碎裂效应,在微观光学势的实部和虚部中引入了修正因子NR,N1.系统研究了入射粒子6Li与靶核12C,28Si,40Ca,58Ni,90Zr和208Pb散射的微观光学势,计算中虚部增强因子取N1≈3.0,而实部修正因子NR对于给定的碰撞系统几乎是一个常数.理论很好地再现了所有被研究靶核和入射能量的弹性散射实验数据.参数无关的微观理论对核.核散射,尤其是对不稳定核.核系统反应的描述是有价值的.     

6Li与核弹性散射的微观光学势

从基本的Dirac-Brueckner-Hartree-Fock微观理论出发，得到同时包含实部和虚部的核子-核散射的微观光学势，并利用折叠模型直接获得了核-核散射参数无关的整体微观光学势.考虑到核-核散射去弹过程高级项的贡献和⁶Li的碎裂效应，在微观光学势的实部和虚部中引入了修正因子N_R，N_I.系统研究了入射粒子⁶Li与靶核¹²C，²⁸Si，相似文献   

氘-核微观光学势的自洽研究

从同一种Skyrme相互作用出发,利用Green函数的质量算符方法,推导了氘-核微观光学势的解析公式;利用半经典变分方法,确定了靶核的核子密度分布。然后,再利用上述计算公式和密度分布,系统地研究了在不同的氘核入射能量下²D+⁴⁰Ca,²D+⁶⁰Zr和²D+²⁰⁸Pb的光学势实部和虚部。这样得到的氘-核光学势是完全自洽和微观的。 关键词：     

基于色散光学模型的40Ca核子散射数据计算

对钙同位素核数据的研究具有重要的理论价值和应用前景,其中⁴⁰Ca作为天然钙最主要的同位素,是一种重要的材料核素.本文采用色散光学模型对球形核⁴⁰Ca的核子弹性散射数据进行计算.通过考虑色散光学模型势中实部势的非定域性以及虚部势的壳间隙结构,实现了对⁴⁰Ca相关核子散射数据的良好描述,其中包括中子总截面、核子弹性散射角分布以及分析本领.此外,本文计算了色散光学模型势的实部体积分,其随能量的变化图像在费米能附近出现了明显的色散峰结构.     

中子滴线附近核异常大半径的解释

基于中子滴线附近核结合能的数据分析,¹¹Li,¹⁴Be和¹⁷B等可看作是核芯-中子-中子组成的三体系统。假定核芯-中子和中子-中子间作用势为弱吸引指数势,不足以形成核芯-中子和中子-中子束缚态。本文的研究表明,核芯-中子-中子三体系统可形成弱束缚态。⁶He,¹¹Li,¹⁴Be和¹⁷Be核的异常大核半径正是由于外层中子的弱束缚所致。 关键词：     

基于壳模型单体密度矩阵的折叠模型质子弹性散射分析

利用折叠模型计算得到折叠势实部并结合Koning和Delaroche光学势的虚部, 计算分析了质子与^30—40S的弹性散射数据. 通过引入Woods-Saxon势下核壳模型单体密度矩阵, 消除了折叠模型计算中常用的定域近似. 分析比较了定域近似对折叠势以及弹性散射截面计算的影响. 计算结果与折叠模型以及JLM模型计算结果进行了比较.     

温度相关的核子相对论微观光学势

本文将Walecka模型和热场动力学理论应用在核物质和有限核中,研究了核子在各种温度下的相对论微观光学势以及相应的薛定谔等效势和平均自由程.对于核物质,取核子的Hartree-Fock自能为光学势的实部,交换σ和ω介子的极化图为光学势的虚部.对于有限核的微观光学势通过定域密度近似获得.     

半微观质子光学势

基于原子核壳模型单体密度矩阵的折叠模型计算光学势的实部,配以唯象光学势虚部,构造半微观光学势.通过拟合质子弹性散射实验数据,得到适用于质量数28~90,能量到200 MeV的半微观质子光学势.该光学势用于质子弹性散射计算分析,在参数大为减少的情况下,计算得到的角分布和分析本领与实验数据的符合程度,总体上好于Koning-Delaroche普适光学势的计算结果.     

相对论微观光学势的自洽计算

本文以Walecka模型及非线性σ模型自洽计算了¹⁶O、⁴⁰Ca的相对论微观光学势.得到的标量势和矢量势符号相反,大小约为几百MeV,与核子的质量可以相比拟.为了与非相对论光学势比较,给出了Schrodinger等价势.这个等价势在很大的能量范围(E=200MeV以下)内适用,相对论计算自然地得到较强的能量相关的自旋-轨道耦合势,与唯象分析一致.本文用洽计算的实部势及最低级的虚部势计算了核子-核散射微分截面及极化率,得到与实验较好的符合.非线性σ模型给出合理的核的不可压缩系数,从而考虑了核的表面效应,改善了计算的光学势.     

200MeV以下质子-核散射的相对论微观描述

应用Dirac Brückner-Hartree-Fock方法, 采用新的G矩阵分解方式研究了核子在核介质中的同位旋相关的相对论微观光学势，采用定域密度近似得到有限核的相对论微观光学 势.讨论了有限核的相对论微观光学势及其Schrdinger等价势与入射质子能量的关系，计 算了200MeV以下质子入射40⁴⁰Ca和208²⁰⁸Pb核的弹性散射角分布 和分析本领，得到了与实验相一致的结果，并将这种方法推广用于不稳定核的研究.通过对C a同位素的计算可以看出，在相 关键词： 相对论微观光学势 Dirac Brückner-Hartree-Fock 不对称核物质 定域密度近似     

Theoretical analysis of <Superscript>6</Superscript>He + <Superscript>12</Superscript>C scattering by means of the model of microscopic optical potential

The ⁶He + ¹²C elastic scattering at E = 3.0, 38.3, and 41.6 MeV/nucleon is analyzed using the microscopic model of optical potential. According to this approach, two or three parameters are fitted that renormalize the depth of real, imaginary, and surface parts of the calculated optical potential. In this case, the ambiguity of the obtained sets of fitting parameters remains, but can be reduced by introducing an additional criterion of selection: the dependence of the volume integrals of the optical potential on the energy. The structure of the obtained optical potential, the role of the nuclear medium, the formation of the imaginary part of the optical potential, and the interconnection between the surface potential and the ⁶He breakup channels are discussed.     

Parametrization of woods-saxon potential for heavy-ion systems

Several elastic scattering angular distributions of ~(12)C from target nuclei of A ≥39 are analyzed to extract the Woods-Saxon potential parameters with the fixed imaginary potential and Coulomb radius parameters.Using the best fitted diffuseness parameters,the correlations of the real part parameters with A_1~(1/3)+ A_2~(1/3) and incident energy are revealed, and the systematic Woods-Saxon potential parameters are presented for nucleus-nucleus interaction.The proposed potential parameters can reproduce not only the elastic scattering angular distributions induced by ~(12)C,but also many elastic scattering angular distributions induced by the projectiles other than ~(12)C,thus providing important inputs for the study of nuclear reactions of heavy-ion systems.     

Comparison of 7Li , 7Be + 9Be elastic scattering in the coupled-reaction-channels approach

The data for the ⁷Li + ⁹Be and ⁷Be + ⁹Be elastic scattering at the energies E _lab(⁷Li) = 15.75 , 24, 30, 34, 63 and 130MeV and E _lab(⁷Be) = 17 , 19 and 21MeV were analyzed within the optical model and coupled-reaction-channels method. The elastic and inelastic scattering, reorientation of ⁷Li , ⁷Be and ⁹Be as well as most important transfer reactions were included in the coupled-channels scheme. The resulting ⁷Li and ⁷Be potentials are very similar and have the same energy dependence. The real potential for recently derived ⁸Be + ⁹Be scattering potentials is very similar to that for ⁷Li , ⁷Be but the imaginary part of the ⁸Be one has a much greater strength at longer range.     

A nuclear structure approach to the nucleon-nucleus optical potential at low energy

An antisymmetrized microscopic calculation of the optical potential for nucleon-⁴⁰Ca elastic scattering is derived. RPA correlations taken into account in the one-particle mass operator are shown to bring a correction to the first-order real potential at low energies and to lead to an imaginary potential. Both are calculated for incident nucleon energies between 10 and 50 MeV. Their general properties are studied in great detail and, after comparison with empirical imaginary potentials, the reliability of such an approach is discussed according to the value of the incident energy.     

The reaction mechanism of heavy ion scattering at intermediate energies

The contribution to the real and imaginary nucleus-nucleus (N-N) optical potential from nucleon-nucleon scattering in the medium is calculated in a local density approximation from a two Fermi sphere nuclear matter picture for the N-N collision. This reaction mechanism is shown to be dominant for ¹²C + ¹²C scattering at all considered energies (160 MeV < E_lab < 2250 MeV) giving a weakly energy dependent reaction cross section of about 900 mb. Inclusion of the collective 2⁺, 3^? excitations in a coupled channel calculations gives good agreement for both the measured elastic and inelastic 2⁺ cross section at E_lab = 1016 MeV. This fully microscopic parameter free calculation indicates that the energy dependence of the reaction cross section for this system is mostly due to the decrease of the collective contribution with increasing energy contrary to current theoretical models.     

Isotopic effects in the 7Li + 10, 11B elastic and inelastic scattering

Angular distributions of the ⁷Li + ¹⁰B elastic and inelastic scattering were measured at the energy E _lab (¹⁰B) = 51 MeV (21 MeV c.m.). These and previously measured ⁷Li + ¹⁰B elastic-scattering data known at the ⁷Li-beam energies 24 MeV (14.1 MeV c.m.) and 39 MeV (22.94 MeV c.m.) were analyzed within the optical model and coupled-reaction channels method to determine the energy dependence of the parameters of the scattering potential and find the difference of these parameters from that of ⁷Li + ¹¹B scattering. It was found that the ⁷Li + ¹¹B potential parameters fail to describe the ⁷Li + ¹⁰B scattering data. The biggest difference is observed between the depths of the imaginary potentials that describe these scatterings.     

Elastic scattering of heavy nuclei and nucleus-nucleus potential with repulsive core

The elastic scattering of ¹⁶O + ¹²C at various collision energies is discussed in the framework of the optical model with repulsive core nucleus-nucleus potential. The cross sections on backward angles are strongly raised due to repulsive core. It is shown by using the near-side/far-side decomposition method that the near-side component of the scattering amplitude mainly contributes to the elastic scattering cross sections on forward and backward angles. The repulsive core of ¹⁶O + ¹²C potential takes place at distances R ≲ 3 fm.