In the present work, we systematically study the α decay preformation factors Pα within the cluster-formation model and α decay half-lives by the proximity potential 1977 formalism for nuclei around Z = 82, N = 126 closed shells. The calculations show that the realistic Pα is linearly dependent on the product of valance protons (holes) and valance neutrons (holes) NpNn. It is consistent with our previous works [X.-D. Sun et al., Phys. Rev. C 94, 024338 (2016), J.-G. Deng et al., Phys. Rev. C 96, 024318 (2017)], which Pα are model-dependent and extracted from the ratios of calculated α half-lives to experimental data. Combining with our previous works, we confirm that the valance proton-neutron interaction plays a key role in the α preformation for nuclei around Z = 82, N = 126 shell closures whether the Pα is model-dependent or microcosmic. In addition, our calculated α decay half-lives by using the proximity potential 1977 formalism taking Pα evaluated by the cluster-formation model can well reproduce the experimental data and significantly reduce the errors.
α decay is usually associated with both ground and low-lying isomeric states of heavy and superheavy nuclei, and the unpaired nucleon plays a key role on α decay. In this work, we systematically studied the α decay half-lives of odd-A nuclei, including both favored and unfavored α decay within the two-potential approach based on the isospin dependent nuclear potential. The α preformation probabilities are estimated by using an analytic formula taking into account the shell structure and proton-neutron correlation, and the parameters are obtained through the α decay half-lives data.The results indicate that in general the α preformation probabilities of even-Z, odd-N nuclei are slightly smaller than the odd-Z, even-N ones. We found that the odd-even staggering effect may play a more important role on spontaneous fission than α decay. The calculated half-lives can well reproduce the experimental data.
In the present work considering the contributions of the daughter nuclear charge and the orbital angular momentum taken away by the emitted proton, we propose a two-parameter formula of new Geiger-Nuttall law for proton radioactivity. A set of universal parameters of this law is obtained by fitting 44 experimental data of proton emitters in the ground state and isomeric state. The calculated results can reproduce the experimental data well. For a comparison, the calculations performed using other theoretical methods, such as UDLP proposed by Qi et al. [Phys. Rev. C 85, 011303(R) (2012)], the CPPM-Guo2013 analyzed by our previous work [Deng et al., Eur. Phys. J. A 55, 58 (2019)] and the modified Gamow-like model proposed by us [Chen et al., J. Phys. G: Nucl. Part. Phys. 96, 065107 (2019)] are also included.Meanwhile, we extend this new Geiger-Nuttall law to predict the proton radioactivity half-lives for 51 ≤ Z ≤ 91 nuclei, whose proton radioactivity is energetically allowed or observed but not yet quantified in NUBASE2016.
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