Production of heavy neutron-rich nuclei around N=126 in multi-nucleon transfer (MNT) reactions Long ZHU (祝龙) Sino-French Institute of Nuclear Engineering and Technology NuSYM2018, South Korea 1

Outline Background Dinuclear system (DNS) + GEMINI model Some Results Shell effects on production cross sections Incident energy dependence Advantage of 238U induced reactions Perspective of radioactive beam induced reactions Summary

Outline Background Dinuclear system (DNS) + GEMINI model Some Results Shell effects on production cross sections Incident energy dependence Advantage of 238U induced reactions Perspective of radioactive beam induced reactions Summary

Discovery of Nuclides proton neutron It was estimated that about 7000 bound nuclides exist. About 260 Stable nuclei in nature. By 2015, 3211 nuclides have been discovered. Multinucleon Transfer ? Spallation N=126 Projectile Fragmentation proton N=82 Projectile Fission neutron https://people.nscl.msu.edu/~thoennes/isotopes/

No new isotope with N=126 is observed yet One candidate: 136Xe+208Pb Dubna No new isotope with N=126 is observed yet Pure proton transfer from lead to xenon might be rather favorable here because the lighter fragments formed in such a process are well bound (stable nuclei) and the reaction Q-values are almost zero. V. Zagrebaev and W. Greiner, PRL 101, 122701 (2008) E. M. Kozulin et al., PRC 86, 044611 (2012)

No new isotope with N=126 is observed yet GANIL One candidate: 136Xe+198Pt (Because of larger transfer probability of neutron) No new isotope with N=126 is observed yet GANIL Great advantages of MNT reactions than projectile fission Deduced cross sections Y. X. Watanabe, et al., PRL 115, 172503 (2015)

Difficulties for producing unknown nuclei in MNT reactions Experimentally - Difficult to separate and detect the products. - New methods and equipment need to be developed Theoretically - Not enough experimental data for development of model - Difficult to make predictions

Outline Background Dinuclear system (DNS) + GEMINI model Some Results Shell effects on production cross sections Incident energy dependence Advantage of 238U induced reactions Perspective of radioactive beam induced reactions Summary

DNS+GEMINI model Transfer probability is governed by transport Master Equation: Potential energy surface: GEMINI for deexcitation (particle evaporation and fission) G. G. Adamian, et al, Phys. Rev. C 68, 034601 (2003). M. Schadel, et al. Phys. Rev. Lett. 48, 852 (1982). S. Ayik, B. Schurmann, and W. Norenberg, Z. Phys. A 277, 299-310 (1976) L. Zhu, et al, JPG. 42, 085102 (2015)

Outline Background Dinuclear system (DNS) + GEMINI model Some Results Shell effects on production cross sections Incident energy dependence Advantage of 238U induced reactions Perspective of radioactive beam induced reactions Summary

Shell effects Inverse Quasifission 160Gd + 186W The injection position is on the side of the valley and the probability of leading to the configuration of 138Ba + 208Pb can be enhanced. Increase of dissipated energy weakens the shell effects. Inverse Quasifission E. M. Kozulin et al., PRC 96, 064621 (2017) L. Zhu et al., PRC 97, 044614 (2018)

136Xe is not favorable for producing transtarget nuclei. Because of the closed neutron shell (N = 82) in projectile 136Xe, the injection point is located at the bottom of the valley on PES for the reaction 136Xe + 186W. Hence, inner barriers need to be overcome in process of nucleon transfer. 136Xe is not favorable for producing transtarget nuclei. Ec.m.=408MeV Ec.m.=451MeV

Incident energy dependence of production cross sections (The production yields of actinide neutron-rich nuclei strongly depend on the incident energy. However, for producing heavy neutron-rich nuclei around N = 126 the incident energy effects are weak.) High incident energy increases the primary cross sections, more neutrons will be evaporated during cooling process. High fission probabilty 160Gd + 186W V. I. Zagrebaev and Walter Greiner, PRC 83, 044618 (2011) A. V. Karpov and V. V. Saiko, PRC 96, 024618 (2017)

Advantages of cross sections in MNT reactions based on 238U We expect the high cross sections based on: The 238U shows large value of N/Z ratio (=1.59) The mass asymmetry relaxation would promote the nucleons transferring from 238U to light partners The neutron closed shell N=126 could attract the neutrons flow from 238U to light partners

Advantages of cross sections in MNT reactions based on 238U Shell effects N/Z equilibration Mass asymmetry relaxation

Advantages of cross sections in MNT reactions based on 238U As we expected, 238U induced reactions show great advantage of cross sections Ec.m. =1.15Vcont 2-4 orders of magnitude larger !! With consideration of experimental measurement, such as beam intensity and kinematics, the 238U could be the target. N=126

Radioactive beam induced reactions (Beam intensities are too low in present equipment) Based on beam intensities proposed by SPIRAL2 >108 ions/s for 144Xe AXe+208Pb L. Zhu et al., PLB 767, 437–442 (2017) S. Gales, Prog. Part. Nucl. Phys. 59, 22 (2007) . L. Zhu et al., PRC 96, 024606 (2017)

Summary Shell closures play an important role in inverse quasifission process 2. The production cross section of neutron-rich nuclei around N = 126 weakly depends on the incident energy. 238U shows great advantages for producing heavy neutron- rich nuclei around N=126. With development of the modern radioactive beam facilities, radioactive beam induced transfer reactions will be promising approaches to fill the blank of nuclear map around last r-process “waiting point”.

Thanks Collaborators: Jun Su, Chen-Chen Guo Sun Yat-sen University Cheng Li, Feng-Shou Zhang Beijing Normal University Pei-Wei Wen, Cheng-Jian Lin China Institute of Atomic Energy Zhao-Qing Feng South China University of Technology Xiao-Jun Bao Hunan Normal University Thanks