Study Of ? Decay Preformation Factors Of Nuclei Around Closed Shells

?decay is one of the most important tools to study unstable nuclei,neutron-deficient nuclei,and superheavy nuclei.Experimentally,?decay is the main decay mode for most of new synthetic superheavy nuclei and the effective way to determine their identities.Therefore,?decay has been an active area of research in nuclear physics.Within Gamow's quantum tunnel theory,the?decay process is described as a preformed?particle penetrating the Coulomb barrier.Thus the study of?preformation factor is of great significance to?decay of nucleus,which denotes the probability of an?particle preformation.In this work,we systematically study the?decay half-lives,?decay preformation factors of nuclei around closed shells and predicate the?decay half-lives of new nuclei based on the?decay 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 the?decay half-lives and phenomenological?preformation factors of unfavored?-decay??decay case of the orbital angular momentum taken away by the ? particle l?0?of nuclei around Z=82,N=82 and 126 shell closures.The phenomenological?preformation factors are extracted from the ratios of calculations to experimental?decay half-lives.The results indicate that the phenomenological?preformation factors P_?of 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 the?preformation factors and the values of corresponding parameters.The calculated?decay half-lives can well reproduce the experimental data.?2?Based on the cluster-formation model and Coulomb and proximity potential model,we systematically study the?decay half-lives and microcosmic?decay preformation factors of nuclei around Z=82,N=126 closed shells.Our calculations indicate that the microcosmic?decay 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 the?preformation factor and the values of corresponding parameters.Combining with our previous work,we confirm that the?decay 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 the?preformation for nuclei around Z=82,N=126 shell closures whether the?preformation factors is model dependent or microcosmic.In addition,many researchers adopted the Coulomb and proximitypotential model to investigate?decay leaving?preformation factors out of consideration.We systematically study the?decay half-lives of nuclei around Z=82,N=126 shell closures by using the Coulomb and proximity potential model taking?preformation 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 the?decay cases of even-even nuclei and odd-A nuclei in the region of82<Z<126 and 152<N<184 adopting the analytic formula for?preformation factor and the latest?decay experimental data.We extend our study to predict the?decay half-lives for synthesis of ²⁹⁶Og and ²⁹⁷Og in experiment.The predicted?decay 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.