Unusual behavior in the systematics of α-preformation factors above Z, N=50 doubly magic shell closures

The systematics of alpha-preformation factor (P-alpha) above the Z, N = 50 shell closures is investigated with the dynamical double-folding potential (DDFP) which incorporates the nuclear medium effect in alpha decay. With the accuracy of the DDFP verified in the half-life calculation, the P-alpha factors are deduced from the available experimental alpha-decay energies and half-lives. The result suggests that the relative alpha-reduced width W-alpha of Te-104 is 6.54, which stands with the experimental conclusion W-alpha > 5 [Phys. Rev. Lett. 121, 182501, 2018], and is very close to the theoretical value 6.92 from the microscopic quartetting wavefunction approach (QWA) [Phys. Rev. C 101, 024316, 2020]. The P-alpha variations above Z, N = 50 are found to show an unusual behavior which is different from the known P-alpha systematics above the Z = 82, N = 126 shell closures. The correlations of P-alpha factors with different types of two-nucleon correlated interactions are analyzed in detail, which suggests that the large enhancement of the proton-neutron interaction along with its positive correlation with the P-alpha value probably accounts for the unusual P-alpha systematics in this region. All these indications imply a likely predominant role played by the proton-neutron correlation against the pairing correlations in contributing to the alpha-cluster formation for nuclei in the Sn-100 neighboring region.

Automated summary

The systematics of the alpha-preformation factor (P-alpha) above the Z, N = 50 shell closures is investigated using the dynamical double-folding potential (DDFP) with nuclear medium effect incorporated. The P-alpha factors are deduced from experimental data, and the result shows an unusual behavior compared to the known systematics. The correlations between P-alpha factors and different two-nucleon correlated interactions are analyzed in detail, indicating a likely predominant role played by the proton-neutron correlation in alpha-cluster formation.