Occurrence of Staggering and Identical Energies in Ground State Rotational Bands in Some Actinide Isotopes within Two-Parameter Rotational Model

The excitation energies of positive parity ground state bands in ^230,232 Th, ^234,236,238 U and ^236,238 Pu actinide nuclei suggest that they follow the empirical rotational model containing two parameters. For each nucleus, the optimized two parameters are calculated by using a computer simulated search programme in order to obtain a minimum root mean square deviation between the calculated and measured excitation energies. The calculated results agree very well with the experimental data. The behavior of nuclear kinematic and dynamic moments of inertia as a function of rotational frequency is investigated. The appearance of Δ I=2 staggering effects in the transition energies for the selected actinide nuclei is examined. For each nucleus, we calculated the deviation of the transition energies from smooth reference, representing the finite difference approximations to higher orders of the γ -ray transition energies at a given spin. The presence of Δ I=4 staggering in transition energies of ground state bands of ^232 Th and ^236,238 U is also investigated. We noticed that the ground state bands of ^236 U and ^238 U have identical transition energies over a wide range of spin. The energy differences are identical within ∼ 3 keV for all transitions.