New behaviors of α-particle preformation factors near doubly magic 100Sn

The alpha-particle preformation factors of nuclei above doubly magic nuclei Sn-100 and Pb-208 are investigated within the generalized liquid drop model. The results show that the alpha-particle preformation factors of nuclei near self-conjugate doubly magic Sn-100 are significantly larger than those of analogous nuclei just above Pb-208, and they will be enhanced as the nuclei move towards the N =Z line. The proton-neutron correlation energy Ep-n and two protons-two neutrons correlation energy E2p-2n of nuclei near loo Sn also exhibit a similar situation, indicating that the interactions between protons and neutrons occupying similar single-particle orbitals could enhance the alpha-particle preformation factors and result in superallowed alpha decay. This also provides evidence of the significant role of the proton-neutron interaction on alpha-particle preformation. Also, the linear relationship between alpha-particle preformation factors and the product of valence protons and valence neutrons for nuclei around Pb-208 is broken in the Sn-100 region because the alpha-particle preformation factor is enhanced when a nucleus near Sn-100 moves towards the N =Z line. Furthermore, the calculated alpha decay half-lives fit well with the experimental data, including the recent observed self-conjugate nuclei Te-104 and Xe-108 [Phys. Rev. Lett. 121, 182501 (2018)].