α particle preformation and shell effect for heavy and superheavy nuclei**Supported by National Natural Science Foundation of China (11675066, 11475050), Fundamental Research Funds for the Central Universities (lzujbky-2017- ot04) and Feitian Scholar Project of Gansu Province

Abstract

The α 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 α particle preformation. The closer the proton and neutron numbers are to the magic numbers, the more difficult the formation of the α 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.