A two-parameter model is constructed considering the pairing correlation between the normal and abnormal parity states based on the fermion dynamical symmetry model (FDSM). Under reasonable approximations this model can be deduced from a Hamiltonian distinguishing the protons and neutrons. The mechanism of the stretching effect is contained in this model and shown by the numerical results. More importantly, the numerical calculations of this model show that the data of the yrast lines of 15 typical rotational nuclei in the actinide region are fitted in a very high quality.

• Received 11 May 1995

DOI:https://doi.org/10.1103/PhysRevC.52.1845