LAUSR

The alpha particle preformation factor is extracted within a generalized liquid drop model for Z = 84 - 92 isotopes and N = 126, 128, 152, 162, 176, 184 isotones. The calculated results show clearly that the shell effects play a key role in alpha particle preformation. The closer the proton and neutron numbers are to the magic numbers, the more difficult the formation of the alpha cluster inside the mother nucleus is. The preformation factors of the isotopes reflect that N = 126 is a magic number for Po, Rn, Ra, and Th isotopes, but for U isotopes the weakening of the influence of the N = 126 shell closure is evident. The trend of the factors for N = 126 and N = 128 isotones also support this conclusion. We extend the calculations for N = 152, 162, 176, 184 isotones to explore the magic numbers for heavy and superheavy nuclei, which are probably present near Z = 108 to N = 152, 162 isotones and Z = 116 to N = 176, 184 isotones. The results also show that another subshell closure may exist after Z = 124 in the superheavy nuclei. This is useful for future experiments.