The $\alpha$ preformation factor and the penetration probability are carefully analyzed for heavy and superheavy even-even nuclei. The penetration probability of an $\alpha$ cluster in the parent nucleus is calculated within the WKB approximation, whereas the nuclear potential between an $\alpha$ cluster and the daughter nucleus is obtained in the frame of a double-folding model with a density-dependent nucleon-nucleon interaction, in which the zero-range exchange term is supplemented. The $\alpha$ preformation factors in different shell regions are compared. It is shown that shell effects play an important role in $\alpha$ preformation. The preformation factor can supply information on the nuclear structure, and the penetration probability mainly determines the $\alpha$-decay half-life. The results indicate that the deformed-subshell region at $N=162$ is different from that at $N=152$, and $Z=114$ and $N=184$ may lie in the closed-shell region.

• Received 24 June 2009

DOI:https://doi.org/10.1103/PhysRevC.80.064325