Experimental Study For The Elastic Scattering And Breakup Of ¹¹Be+²⁰⁸Pb

At present,the study of the elastic scattering of weakly-bound nuclei mainly focuses on the neutron rich nuclei,and the reaction energy is mostly selected around the Coulomb barrier.The elastic scattering angular distribution of neutron rich nuclei is apparently different from that of stable nuclei.In the elastic scattering differential cross-section of neutron rich nuclei,the characteristic Coulomb rainbow is obviously depressed and even disappears.It is theoretically explained that due to the large breakup/transfer cross-section of the weakly-bound nuclei,the strong coupling effects of the breakup/transfer channel on the elastic scattering channel lead to this peculiar property of the angular distribution.The elastic scattering angular distribution of several proton rich nuclei on Pb target at energy of around three times the Coulomb barrier has been measured by our group previously.In order to study the dependence of the elastic scattering angular distribution on the valence nucleon,energy and target nucleus,the elastic scattering experiments of ⁹Be+²⁰⁸Pb at 88 MeV,¹⁰Be+²⁰⁸Pb at127 MeV,and ¹¹Be+²⁰⁸Pb at 140 MeV were carried out at the Radioactive Ion Beam Line in Lanzhou?RIBLL-1?.In this experiment,two thin double-sided silicon strip detectors?DSSD?with 16strips on both sides were placed upstream from the target to identify the position and direction of the incident particles.After the target,a detector array composed of three sets of?E-E telescopes was used to detect the scattered particles.Each set of the telescopes consists of one DSSD with 32 strips on both sides and one silicon detector?SD?.By analyzing the experimental data,the angular distribution of the scattered particles is extracted,and the Rutherford scattering angular distribution is obtained by Monte Carlo simulation.Thus the elastic scattering angular distribution of ^9,10,11Be on²⁰⁸Pb target as the ratio to the Rutherford cross-section is obtained.In order to eliminate the influence of the scattering from the DSSDs upstream from the target,the events coming from the detector system were measured with the target moved out.Combined with the analysis of these experimental data and simulation,it is considered that the influence of the target-out events can be ignored.In this experiment,we calculated with LISE that ⁹Be+²⁰⁸Pb is pure Rutherford scattering in the angular range of interest?<20°?due to the relatively low incident energy,and the ratio of its elastic scattering cross-section to Rutherford scattering cross-section is about 1,according to which the global normalization constant and detector misalignment correction were determined.The elastic scattering angular distribution of ¹⁰Be+²⁰⁸Pb shows a typical Fresnel distribution,and we used Woods-Saxon potential,S?o Paulo Potential and X&P potential to analyze and try to extract the density distribution of ¹⁰Be from its elastic scattering angular distribution.In the case of ¹¹Be+²⁰⁸Pb,the Coulomb rainbow is obviously depressed in the elastic scattering angular distribution at the energy around three times the Coulomb barrier,significantly different from the experimental results of proton rich nuclei previously measured by our research group.This indicates that the valence nucleons play an important role in the angular distribution of elastic scattering.Optical model was employed to analyze the elastic scattering data with an extended potential extracted from ¹⁰Be+²⁰⁸Pb,and the calculations are in good agreement with the experimental data.For the coupling effects of the breakup channel on the elastic scattering channel,we used CDCC and XCDCC to analyze,and these two calculated results have no obvious difference,both consistent with the experimental data.The breakup reaction angular distribution of ¹¹Be+²⁰⁸Pb at this high energy was measured for the first time at RIBLL1,and analyzed with CDCC and XCDCC methods,which gave similar results and both underestimated the breakup cross-section from around the grazing angle.Considering?X?CDCC method accounts only for the elastic breakup mechanism,non-elastic breakup contributions were taken into account using an inclusive-breakup model.The sum of the elastic breakup and non-elastic breakup cross-section agrees rather well with the experimental data.