Study On Structure And Decay Properties Of Superheavy Nuclei

The study on structures and properties of superheavy nuclei is an advanced subject.The theoretical studies show that most of the superheavy nuclei are deformed or superdeformed.Although a lot of researches have been done on the structures of deformed superheavy nuclei,there are few studies about triaxial deformation and tensor term in the nuclear force.Based on the Skyrme-Hartree-Fock plus BCS theory including tensor force,the evolutions of triaxial shapes and structure properties of Z=118 and Z=120 nuclei have been systematically studied,the main results are listed as follows:(i)The neutron-deficient nuclei of Z=118 and Z=120 elements have weak triaxial deformed structures and the neutron-rich nuclei have obvious triaxial deformed or superdeformed structures.The studies on deformation for Z=118 and 120 isotopes have been performed,the results indicate that the ground or excited states of neutron-deficient nuclei with N<184 have weak triaxial deformed structures.However,the excited states of neutron-rich nuclei show obvious triaxial deformed or superdeformed structures.This indicates that triaxial degree of freedom can not be ignored in describing the deformation of neutron-rich superheavy nuclei.(ii)Tensor force has not obvious influence on the shapes of ground states,but it has great effect on potential wells of superdeformed states,fission barrier height and the excited states shapes of neutron-rich nuclei.Additionally,tensor force has certain effect on the binding energies,two-neutron energies and radii for superheavy nuclei.Therefore,tensor force should not be ignored on the study of superdeformed states for Z=118 and Z=120 nuclei.In addition,the study on decay properties of superheavy nuclei is a hot subject in the nuclear physics field.The properties of a-decay,spontaneous fission and cluster radioactivity of superheavy nuclei have been studied by the generalized liquid drop model and several phenomenological models.The main results are listed as follows:(i)The competition between a-decay and spontaneous fission of Z=104-120 have been systematically studied,the results show that a-decay is the main decay mode for 258,260104,268-276110,270-280112,272-286114,274-2941-6,278-302118 and 284-308120,and these nuclei are possibly identified via a-decay in experiments.Additionally,the results suggest shell effects at N = 162,178,184 and 196.(ii)The study of cluster radioactivity of Z=104-124 indicates that the cluster radioactivity is dependent on models.The UD,UNIV and Horoi formulas are just preformation models,which can be used in describing the lighter cluster emissions.The UDL formula can predict the lighter and heavier cluster radioactivities owing to the inclusion of the preformation and fissionlike mechanisms,so the UDL model is more universal.Additionally,the results indicate that shell effect of N=184 has an important influence on cluster radioactivity.Finally,the probable cluster radioactivitives in the superheavy region have been predicted by the UDL models and the results show that the isotopes of 292-296,308-318118,284-304,308-324120 and 316-322122 are the most likely candidates as the cluster emitters.Finally,the effect of intense laser field on a-decay and proton radioactivity is studied.The results show that the modification on the penetration probability of emitted particle by intense laser field is related to the length of tunneling path,and proton radioacitivity is easily modified than a-decay by strong laser field.In addition,the modification of penetration probability has linear relationship with laser intensity,when the laser intensity is up to one hundred times than the original one,the relative change rate of penetration probability is up to ten times than the original value.