11Be弹性散射道和破裂道的微分截面角分布及耦合道效应

Some of experiments have been performed for the elastic scattering of the weakly bound nuclei, such as 6He, 11Be and 11Li, at energies around the Coulomb barriers. However, the experimental data for the energies above the Coulomb barriers are very scarce. A typical experimental phenomenon of the elastic scattering for the neutron-rich nuclei is that the Coulomb rainbow peak is partially or completely suppressed. It has been suggested that this phenomenon is caused by both nuclear and Coulomb breakup couplings. Recently, a new tool to study the structures of one-nucleon weakly-bound nuclei has been proposed, based on the cross section ratio of the breakup and the elastic scattering in the angular distributions. .A method to measure the elastic scattering angular distribution has been developed on the Radioactive Ion Beam Line in Lanzhou (RIBLL). The angular distribution of the differential cross sections of 8B shows that its Coulomb rainbow peak can not be suppressed, in contrast to what observed in the elastic scattering by the heavy targets at energies around the Coulomb barriers. We plan to measure the elastic scattering cross sections of 11Be on a 208Pb target at 3.3, 5.0 and 6.6 times of the Coulomb barriers, and the coupled channel effects will be studied. Due to the importance of the breakup channels in the theoretical analysis of the experimental data, breakup cross sections will also be measured. The energy dependence of the angular distributions and optical model parameters will be studied. New experimental data for the elastic scattering and breakup cross sections will be provided to examine the theoretical prediction on the cross section ratio to probe the structures of the one-nucleon weakly-bound nuclei.

当前，弱束缚核在重靶上弹性散射实验研究集中在库仑位垒附近能区，表现出了与稳定核不同的奇特性质。丰中子弱束缚核的微分截面角分布中，特征性的库仑虹明显减弱甚至消失，表明了弱束缚核大的破裂截面及其对于弹性散射道的强烈耦合效应；理论还预言，破裂截面与弹性散射截面的比值能够用来探索弱束缚核价核子的单粒子结构。.我们完成了170.3 MeV的丰质子弱束缚核8B弹性散射角分布测量，其特点与丰中子弱束缚核不同。本申请立足兰州放射性束流线RIBLL，拟同时测量3.3、5.0和6.6倍库仑位垒能量的11Be在208Pb靶上的弹性散射和破裂产物的微分截面角分布；研究弱束缚核弹性散射截面、破裂截面及其耦合道效应；研究弱束缚核弹性散射截面及光学势对于能量的依赖关系；研究丰中子与丰质子的不同结构对于弱束缚核反应机制以及耦合道效应的影响；提供实验数据，直接检验关于探索弱束缚核单粒子结构的理论预言。

放射性束物理是当前核物理研究的前沿领域之一，弹性散射和破裂反应是研究放射性核素的奇特结构及反应机制的理想工具。在兰州放射性束流线（RIBLL）上首次测量了三倍库仑势垒能区的丰中子核11Be在208Pb靶上的弹性散射和破裂反应角分布，实验结果表明丰中子核11Be的弹性散射角分布和丰质子核（8B、9C等）明显不同，具有明显的耦合道效应，库仑虹被明显地压低，并系统地研究了弹性散射角分布对于价核子及能量的依赖关系。使用CDCC和XCDCC对实验获得的弹性散射和破裂反应角分布进行了分析，理论计算和实验数据符合得较好。 另外，研制了一套弱束缚核直接核反应望远镜，并投入到实验中。