Studies On The Mechanism Of Multinucleon Transfer Reactions And Pairing Energy Effect In Fragmentation And Spallation Reactions

The new neutron-rich isotope synthesis in the heavy-mass region is currently a frontier research topic in nuclear physics.It mainly involves the physical mechanism of the fast process of nucleus nucleus synthesis,the nucleus structure and decay mode of the drip line region,and the synthesis of superheavy nuclei on the island.The fusion reaction and multi-nucleon transfer reaction based on the radioactive neutron nucleus are the most effective way to produce new nuclides.The theoretical study of its reaction mechanism can provide a basis for the layout of experimental protocols.The denucleation process of the core in the heavy ion collision fragmentation reaction can extract the nuclear material properties.The main content of this paper is divided into two parts.The first part mainly introduces the multinuclear transfer reaction in heavy ion collision.Based on the dinuclear system?DNS?concept,in which the capture of two colliding nuclei,the transfer dynamics,and the deexcitation process of primary fragments are described by an analytical formula,diffusion theory,and a statistical model,respectively.The nucleon transfer takes place after forming the DNS and is coupled to the dissipation of relative motion energy and angular momentum by solving a set of microscopically derived master equations within the potential energy surface.The isotope results of the projectile-like cores of ^40,48Ca+¹²⁴Sn,^58,64Ni+²⁰⁸Pb were mainly analyzed,and compared with the experimental results.The calculation results are very good to reproduce the results.Multinuclear transfer reactions near the coulomb barrier energy mainly calculate the reaction of ⁴⁰Ca(⁴⁰Ar,⁵⁸Ni)+²³²Th,⁴⁰Ca(⁵⁸Ni)+²³⁸U and ^40,48Ca(⁵⁸Ni)+²⁴⁸Cm.The incident energy is near the Coulomb barrier energy,the isotope distribution produced by the transfer reaction is the most extensive with maximal yields along the?-stability line.As the high isospin is easy to dissipate to the low isospin nucleus,it is easy to dissipate the neutron toward the target nucleus,forming a more neutron-rich target-like nucleus.The second part mainly introduces the pairing energy of the fragments in the heavy-ion nuclear reaction.Based on the modified Fisher model,the formula for the ratio of pairing-energy coefficient of the temperature?/T?was deduced using the isobaric yield ratio?IYR?method.It provides a goodbasis for studying the dependence of energy and temperature.The fragments in the measured and simulated 140A MeV ^40,48Ca+⁹Be/¹⁸¹Ta and ^58,64Ni+⁹Be/¹⁸¹Ta reactions have been adopted to perform the analysis.For most fragments,/Tfalls in the range of-1.0</T<1.0.The odd-even staggering in the/T distribution is strong with the smaller neutron excess.A series of spallation reactions,0.5,1A GeV ²⁰⁸Pb+p,1A GeV ²³⁸U+p,0.5A GeV ¹³⁶Xe+d,0.2,0.5,1A GeV ¹³⁶Xe+p and 0.3¹.5A GeV ⁵⁶Fe+p have been analyzed.The results of/T for most of the fragments in the range-1 to 1.In both reactions,the results of/T in general do not exceed the range-2 to 4,except for a few fragments.At the same time,the pairing energy of the fragmentation in in-medium masses was studied,and when there was a peripheral reactions.By studying the energy results in the two reaction systems,the relationship between pairing energy and reaction systems,energy,or neutron excess was analyzed.The results are useful for improving the secondary decay simulation for primary fragments in the heavy-ion collisions.