K^- Nucleus Elastic Scattering and Momentum-Dependent Optical Potentials

The K? nucleus differential elastic scattering cross section for 12C and 40Ca at is calculated with three momentum-dependent optical potential models, which are density-dependent, relativistic mean field, and hybrid model, respectively. It is found that the forms of momentum-dependent optical potential models proposed by us are reasonable and gain success in the calculations and the momentum-dependent hybrid model is the best model for the K? nucleus elastic scattering.

Dirac Optical Potential of p-^14Be and Pronounced “Long-Tail” Shape

The Dirac optical potential for p-14Be elastic scattering is evaluated by the relativistic impulse approximation. Each of the real part and the imaginary part of the potential shows a pronounced "long tail" for the proton elastic scattering from halo nucleus 14Be compared with the potentials for proton scattering from its adjacent nuclei 12C and 16O, which do not have halo structures. This kind of "long tail" phenomenon suggests another signature for halo nuclei.

Applicability of 9Be global optical potential to description of 8,10,11B elastic scattering

We achieved a set of 9Be global phenomenological optical model potentials by fitting a large experimental dataset of the elastic scattering observable for target mass numbers from 24 to 209.The obtained 9Be global optical model potential was applied to predict elastic-scattering angular distributions and total reaction cross-sections of 8,10,11B projectiles.The predictions are made by performing a detailed analysis comparing with the available experimental data.Furthermore,these elastic scattering observables are also predicted for some lighter targets outside of the given mass number range,and reasonable results are obtained.Possible physical explanations for the observed differences are also discussed.

A Study of Intermediate Energy Proton-^16O Elastic Scattering Based on the α-Particle Model

In the framework of KMT multiple scattering theory, an optical potential for the intermediate energy proton-160 elastic scattering is presented based on the α particle model of 160. The differential cross sections, the analyzing powers, and the total cross sections of the intermediate energy proton-160 scattering have been calculated by using the obtained optical potential. The main features of the measured angular distributions of the cross section and the analyzing power can be well described. The calculated total cross sections are in good agreement with the experimental data at energies below 0.7 GeV and underestimate the data about 8% at higher energies.

Description of elastic scattering for 7Li-induced reactions on 1p-shell nuclei

The experimental data of elastic scattering angular distributions for 9Be,10B,11B,12C,13C,15N,and 16O targets from 4.5 to 131.8 MeV and 7Li target from 8.0 to 42.0 MeV are fitted to realize the global phenomenological optical potentials(GPOPs)for the 7Li-induced reactions on 1p-shell nuclei.Thus,the 7Li elastic scattering from the 1p-shell nuclei can be systematically described using the established GPOPs.The elastic scattering angular distributions are also reanalyzed using a microscopic method within the framework of the new version of double folding S?o Paulo potential(SPP2).To better describe the elastic scattering at backward angles,the contribution of elastic transfer is further estimated by the distorted wave Born approximation(DWBA)method.Based on the obtained GPOPs,the inelastic scattering angular distributions are also obtained through the coupled channels(CC)method for the different excited states.

Comparison between global phenomenological and microscopic optical potentials for proton as projectile below 100 MeV

For 112 target nuclei （52 elements） with proton as projectile, we calculate the reaction cross sections and elastic scattering angular distributions, as well as the X^2 values for 16 kinds of proton optical model potentials： two sets of phenomenological global optical potentials and the microscopic optical potentials proposed by Shen et al for 14 sets of Skyrme force parameters： GSI-6, SBJS, SKM, SGI-Ⅱ, SKa-b, SCOI-Ⅱ. We find that for obtaining the proton microscopic optical potential based on the nuclear matter approach with Skyrme force, SGI, SKa and SKb are the three sets of optimal Skyrme force parameters.

Elastic scattering of electrons from water molecule

This paper uses the momentum-space optical potential method to calculate the e-H2O scattering elastic cross sections at the energy range from 6 eV to 50 eV, and the differential cross sections in the angle from 0 °to 180° at 40 eV and 50 eV. The polarisation is taken into account via an ab initio equivalent-local potential. The cross sections are compared with experimental measurements and other theoretical calculations.

Applicability of 9Be global optical potential to reactions of 7,10,11,12Be

Elastic scattering angular distributions and total reaction cross-sections of 7,10,11,12Be projectiles are predicted by the systematic 9Be global phenomenological optical model potential for target mass numbers ranging from 24 to 209.These predictions provide a detailed analysis by their comparison with the available experimental data.Furthermore,these elastic scattering observables are also predicted for some targets out of the mass number range.The results are in reasonable agreement with the existing experimental data,and they are presented in this study.

Experimental study of the elastic scattering of 10Be on 208Pb at the energy of around three times the Coulomb barrier

Elastic scattering of 10Be on a 208Pb target was measured at ELab=127 MeV,which corresponds to three times the Coulomb barrier.The secondary 10Be beam was produced at the Radioactive Ion Beam Line in Lanzhou of the Heavy-Ion Research Facility in Lanzhou.The angular distribution of elastic scattering in the 10 Be+208Pb system shows a typical Fresnel diffraction peak.Optical model analysis of the angular distribution was performed using the Woods-Saxon,double-folding and global potentials.With the global potential,different density distributions were used.The results indicate that different density distributions for the projectile induce distinct effects in the angular distribution.

New measurements and reanalysis of^14N elastic scattering on^10B target

The angular distributions of elastic scattering of^14N ions on^10B targets have been measured at incident beam energies of 21.0 and 24.5 MeV.Angular distributions at higher energies 38–94.0 MeV(previously measured)were also included in the analysis.All data were analyzed within the framework of the optical model and the distorted waves Born approximation method.The observed rise in cross sections at large angles was interpreted as a possible contribution of theα-cluster exchange mechanism.Spectroscopic amplitudes SA2 and SA4 for the configuration^14N→^10B+αwere extracted.Their average values are 0.58±0.10 and 0.81±0.12 for SA2 and SA4,respectively,suggesting that the exchange mechanism is a major component of the elastic scattering for this system.The energy dependence of the depths for the real and imaginary potentials was found.

Trial application of the envelope method to the potential ambiguity problem

The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering data.For a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and farside scattering components.By contrast,the envelope method can decompose the experimental data into two components with negative and positive deflection angles,respectively.Hence,a question arises as to whether the comparison between the calculated nearside(or farside)component and the derived positive-deflection-angle(or negative-deflection-angle)component can help analyze the potential ambiguity problem.In this study,we conducted a trial application of the envelope method to the potential ambiguity problem.The envelope method was improved by including uncertainties in the experimental data.The colliding systems of 16O+28Si at 215.2 MeV and 12C+12C at 1016 MeV were considered in the analyses.For each colliding system,the angular distribution experimental data were described nearly equally well by two potential sets,one of which is“surface transpar-ent”and the other is refractive.The calculated angular distributions were decomposed into nearside and farside scattering components.Using the improved envelope method,the experimental data were decomposed into the positive-deflection-angle and negative-deflection-angle components,which were then compared with the calculated nearside and farside components.The capability of the envelope method to analyze the potential ambiguities was also discussed.

Elastic scattering and total reaction cross sections of^(6)Li examined via a microscopic continuum discretized coupled-channels model

We present a systematic study of 6Li elastic scattering and total reaction cross sections at incident energies around the Coulomb barrier within the continuum discretized coupled-channels(CDCC)framework,where 6Li is treated in anα+d two-body model.Collisions with 27Al,64Zn,138Ba,and 208Pa are analyzed.The microscopic optical potentials(MOP)based on Skyrme nucleon-nucleon interaction forαand d are adopted in CDCC calculations and satisfactory agreement with the experimental data is obtained without any adjustment on MOPs.For comparison,αand d global phenomenological optical potentials(GOP)are also used in CDCC analysis and a reduction of no less than 50%on the surface imaginary part of deuteron GOP is required for describing the data.In all cases,the 6Li breakup effect is significant and provides repulsive correction to the folding model potential.The reduction on the surface imaginary part of GOP of deuteron reveals a strong suppression of the reaction probability of deuteron as a component of 6Li when compared with that of a free deuteron.Further investigation is performed by considering the d breakup process equivalently within the dynamic polarization potential approach,and the results show that d behaves in a manner similar to a tightly bound nucleus in 6Li induced reactions.

近库仑势垒能区^(7)Li+^(207)Pb体系光学势的阈异常现象

对于紧束缚核反应体系,光学势在近库仑势垒能区呈阈异常的现象。对于弱束缚核(如^(6)Li、9Be和6He)参与的反应,光学势呈反常的阈异常现象。然而,对于弱束缚核^(7)Li参与的反应,光学势行为仍存在争议。为此,本工作在近垒和深垒能区高精度测量了^(7)Li+^(207)Pb体系的弹性散射角分布,采用光学模型拟合并抽取了势参数,结果显示出阈异常的现象。此外,由深垒能区的数据确定了^(7)Li+^(207)Pb体系的反应阈值,约0.82VB(库仑势垒高度),介于典型紧束缚核16O+208Pb体系的0.93VB和弱束缚核^(6)Li+232Th体系的0.73VB之间。这意味着反应阈和破裂阈之间可能存在着关联,值得进一步研究。

Elastic scattering of ^(13)C and ^(14)C isotopes on a ^(208)Pb target at energies of approximately five times the Coulomb barriers

The elastic scattering angular distributions of ^(13)C at 340 MeV and ^(14)C at 294 MeV and 342 MeV on a ^(208)Pb target,which correspond to approximately five times the Coulomb barriers,were measured at the Radioactive Ion Beam Line in Lanzhou.The data were analyzed within the optical model and continuum-discretized coupled-channels(CDCC)framework,and the results of both calculations could effectively account for the experimental data.The differential cross sections of elastic scattering revealed no particular suppression at the Coulomb nuclear interference peak angles,suggesting that the breakup coupling effects on the elastic scattering angular distributions were negligibly small in this incident energy region.The contributions from the couplings with inelastic states to the elastic cross sections were of minor importance within the angular range covered by these experiments.

Elastic scattering of ~6He from ^(12)C at 38.3 MeV/nucleon

The microscopic optical potential of nucleus-nucleus interaction is presented via a folding method with the isospin dependent complex nucleon-nuclear potential,which is first calculated in the framework of the Dirac-Bruecker-Hartree-Fock approach. The elastic scattering data of ^6He at 229.8 MeV on 12C target are analyzed within the standard optical model. To take account of the breakup effect of 6He in the reaction an enhancing factor 3 on the imaginary potential is introduced. The calculated ^6He＋^12C elastic scattering differential cross section is in good agreement with the experimental data. Comparisons with results in the double-folded model based on the M3Y nucleon-nucleon effective interaction and the few the body Glaubermodel calculations are discussed. Our parameter free model should be of value in the description of nucleusnucleus scattering,especially unstable nucleus-nucleus systems.

晕核^6He（25MeV／u）在^9Be上的弹性散射研究

分析了北京大学核物理实验小组在日本RIKEN实验室完成的 25MeV/u6He和9Be的弹性散射实验数据, 得到了弹性散射微分截面角分布. 利用双折叠模型, 并通过拟合弹性散射微分截面得到了此弹靶体系在此能量下的弹性散射光学势.

用放射性核束进行弹性散射实验的一种角分布归一化方法

介绍了放射性核束弹性散射实验中测量的角分布进行归一化的方法。由于有限的测量角区及放射性核束有较大的发散度 ,采用了逐个事件计算的方法 ,在探测器空间分布区域用事先产生的一系列点构成的数据库模拟探测器边界 ,对这些点进行坐标转换 ,再进行选择判断 ,得到每个事件的几何探测效率。通过每个事件的几何探测效率推算到整个空间 ,得到实际的角分布。

反散射理论导出He-Ne相互作用势

以He原子束与Ne原子束交叉碰撞实验数据为基础，以反散射方法为手段，理论上导出He－Ne原子相互作用势．所得的势呈显出vanderWaals势的特征，即短程为强排斥，中程为碗形吸引，远程为零．这样的势能给出正确的、符合实验的弹性散射微分截面.

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.

中能质子在碳和氧上的弹性散射

本文应用基于核的 a 粒子结构模型和拟合实验的 p—a振幅建立起来的光学势,计算了200MeV和500MeV 的质子在 ^(12)C 和 ^(16)O 上的弹性散射。理论结果较好地与实验符合。