Study on the unfavored α-decay lifetimes around a closed shell

The α-cluster model is extended to study the unfavored α-decay lifetimes around a closed shell. The newly discovered α-decay of 209Bi and a odd-A N=127 isotones are investigated by the α-cluster model. The experimental decay lifetimes can be reproduced satisfactorily. The application of the α-cluster model to research unfavored α-decays has been proved reliable. The theoretical calculations also reflect the measured α particle preformation factor near magic number (N=126). The α-cluster model is improved by introducing a Z-dependent preformation factor