Studies On Production Mechanism Of Heavy Exotic Nuclei And Superheavy Nuclei

The production of new nuclides is one of the most important issues in nuclear physics.So far,the majority of unknown nuclei locate at three regions,which are heavy proton-rich nuclei region nearby proton drip line,neutron-rich nuclei region around neutron drip line and superheavy nuclei with Z>104.Caused by the limitation of target and projectile,the production cross sections of neutron-deficient heavy nuclei and superheavy element are very small.The radioactive beams induced multinucleon transfer reactions may cover these unknown nuclear fields.This thesis contains three components.Firstly,based on the dinuclear system model,the production mechanism of neutron-deficient heavy isotopes with Z=84-92 has been studied through fusion-evaporation reactions.The production cross section of neutron-deficient actinide nuclei with Z=93-100 has been predicted through fusion-evaporation and multinucleon transfer reactions.Secondly,nuclear dynamics in multinucleon transfer reactions around Coulomb barrier energies has been studied by dinuclear system model,in which the dynamical deformation has been developed.Finally,we studied the production mechanism of neutron-rich heavy nuclei and superheavy nuclei in multinucleon transfer reactionsBased on the dinuclear system model,the production mechanism of neutron-deficient heavy isotopes with Z=84-100 has been investigated systematically through fusion-evaporation reactions and multinucleon transfer reactions.The experiment data can be reproduced nicely with the model,in which charge particles evaporation channels are dominant in the decay process.The calculation of neutron-deficient nuclei with Z=84-92 are analyzed thoroughly,in which the shell correction,even-odd effect and mass isospin asymmetry of projectile-target combinations play a significant role in production cross section.Both of fusion-evaporation reactions and multinucleon transfer reactions can be used to produce new neutron-deficient actinide nuclei with Z=93-100,which production cross section is below 1 ?bIn the framework of the dinuclear system model,nuclear dynamics in multinucleon transfer reactions 136Xe+208Pb at incident energies Elab=870 and 1020 MeV has been studied.Total kinetic energy distributions,angular distributions,production cross section of primary products have been analyzed thoroughly.Calculations can reproduce experiment data nicely.It is found that the total kinetic energies of primary fragments are dissipated from the relative motion energy of two touching nuclei and exhibit a symmetric distribution along the fragment mass.The angular distribution of the projectile-like fragments moves forward with increasing beam energy.However,the target-like fragments exhibit an opposite trend.The shell effect is pronounced due to the fragment yields in multinucleon transfer reactions.A dynamical deformation is implemented into the model,which is associated with the projectile-target shape and the relaxation time of ?TD=40×10-22s.Based on the dinuclear system model with dynamical deformation,production cross section of actinide nuclei with Z=93-100 in collision of 91Tc+238U at Elab=6 MeV/nucleon has been studied,in which has a smooth isotopic distribution and one order of magnitude enhancement.Within dinuclear system model,we have calculated the radioactive beam induced multinucleon transfer reactions 124,132Sn+238U/248Cm at incident energy Elab=6 MeV/nucleon for producing neutron-rich heavy nuclei and superheavy nuclei.Production cross sections,total kinetic energy spectra,and angular distributions of primary fragments in the reactions of 124,132Sn+238U/248Cm near Coulomb barrier energies are thoroughly analyzed.It is found that the total kinetic energies of primary fragments are dissipated from the relative motion energy and rotational energy of the two colliding nuclei.The fragments are formed in the forward angle domain.The energy dependence of the angular spectra is different between projectilelike and targetlike fragments.Isospin equilibrium is governed under the potential energy surface.The production cross sections of neutron-rich isotopes are enhanced around the shell closures.New neutron-rich isotopes with Z=60-104 in the multinucleon transfer reactions are listed in Table 5.1.To compare multinucleon transfer and fusion-evaporation reactions,we have calculated reaction system 54Cr+234Am?288 119,and found that fusion-evaporation reaction would be the best method to produce superheavy element with Z>110.