IBM-1 description of the fission products 108,110,112Ru

IBM-1 calculations for the fission products 108,110,112Ru have been carried out. The even–even isotopes of Ru can be described as transitional nuclei situated between the U(5) (spherical vibrator) and SO(6) (γ-unstable rotor) symmetries of the interacting Boson Model. At first, a Hamiltonian with only one- and two-body terms has been used. Excitation energies and B(E2) ratios of gamma transitions have been calculated. A satisfactory agreement has been obtained, with the exception of the odd–even staggering in the quasi-γ bands of 110,112Ru. The observed pattern is rather similar to the one for a rigid triaxial rotor. A calculation based on a Hamiltonian with three-body terms was able to remove this discrepancy. The relation between the IBM and the triaxial rotor model was also examined.