Study Of α Decay Preformation Factors Of Nuclei Around Closed Shells

αdecay is one of the most important tools to study unstable nuclei,neutron-deficient nuclei,and superheavy nuclei.Experimentally,αdecay is the main decay mode for most of new synthetic superheavy nuclei and the effective way to determine their identities.Therefore,αdecay has been an active area of research in nuclear physics.Within Gamow’s quantum tunnel theory,theαdecay process is described as a preformedαparticle penetrating the Coulomb barrier.Thus the study ofαpreformation factor is of great significance toαdecay of nucleus,which denotes the probability of anαparticle preformation.In this work,we systematically study theαdecay half-lives,αdecay preformation factors of nuclei around closed shells and predicate theαdecay half-lives of new nuclei based on theαdecay theories of two-potential approach,cluster-formation model as well as Coulomb and proximity potential model.This work includes the following three topics:（1）Based on the two-potential approach,we investigate theαdecay half-lives and phenomenologicalαpreformation factors of unfavoredα-decay（αdecay case of the orbital angular momentum taken away by the α particle l≠0）of nuclei around Z=82,N=82 and 126 shell closures.The phenomenologicalαpreformation factors are extracted from the ratios of calculations to experimentalαdecay half-lives.The results indicate that the phenomenologicalαpreformation factors P_αof nuclei around Z=82,N=82 and 126 shell closures are linearly dependent on the product of valance protons（holes）and valance neutrons（holes）N _p N_n.We give two linear formulas of theαpreformation factors and the values of corresponding parameters.The calculatedαdecay half-lives can well reproduce the experimental data.（2）Based on the cluster-formation model and Coulomb and proximity potential model,we systematically study theαdecay half-lives and microcosmicαdecay preformation factors of nuclei around Z=82,N=126 closed shells.Our calculations indicate that the microcosmicαdecay preformation factor calculated by cluster-formation model is linearly dependent on the product of valance protons（holes）and valance neutrons（holes）N _p N_n.We give the linear formulas of theαpreformation factor and the values of corresponding parameters.Combining with our previous work,we confirm that theαdecay preformation factor is linearly dependent on the product of valance protons（holes）and valance neutrons（holes）as well as valance proton-neutron interaction plays a key role in theαpreformation for nuclei around Z=82,N=126 shell closures whether theαpreformation factors is model dependent or microcosmic.In addition,many researchers adopted the Coulomb and proximitypotential model to investigateαdecay leavingαpreformation factors out of consideration.We systematically study theαdecay half-lives of nuclei around Z=82,N=126 shell closures by using the Coulomb and proximity potential model takingαpreformation factors evaluated by the cluster-formation model.The calculated results can well reproduce the experimental data.（3）Based on the two-potential approach,we systematically study theαdecay cases of even-even nuclei and odd-A nuclei in the region of82<Z<126 and 152<N<184 adopting the analytic formula forαpreformation factor and the latestαdecay experimental data.We extend our study to predict theαdecay half-lives for synthesis of ²⁹⁶Og and ²⁹⁷Og in experiment.The predictedαdecay half-life of ²⁹⁶Og is 1.09 ms within a factor of 5.12.The predication of ²⁹⁷Og is 0.16 ms within a factor of4.97.The predicted spin and parity of the ground states for ²⁶⁹Sg,²⁸⁵Fl and ²⁹³Lv are 3/2⁺,3/2⁺and 5/2⁺,respectively.At last,a brief summary of this work and some outlooks are given.