Search

Odd-odd 174,176Re nuclei were studied via in-beam γ-ray spectroscopy with a variety of HI-induced reactions at both Michigan State University NSCL and SUNY Stony Brook. One of the most prominent features of each is the existence and very strong population of a doublydecoupled hand. These K = 1 bands result from the coupling of the h 9/2 1/2-[541] proton and an i 13/2 1/2- neutron state. Such doubly-decoupled bands exist in many nuclei in this region. The minimal variations in these structures from nucleus to nucleus implies a relatively weak coupling of the odd particles to the core. This offers hope of a more detailed understanding of p-n residual interactions in relatively high-mass systems. Other information about the character of the doubly-decoupled structures, backbending, and reaction mechanisms can also be learned from these nuclei. Our studies also yielded information on two rotational bands in 175Re, which had been entirely uncharacterized prior to our investigations. The bands are built on the decoupled h 9/2 1/2-[541] proton and a Δ I = 1 band based on the h 9/29/2-[514] proton.

Odd-odd nuclei have been calculated before in the framework of the IBA model. However, in order to keep the calculations tractable, they were done by using supersymmetries or were limited only to unique-parity orbits. We used computer codes for the interacting-bosonfermion-fermion approximation (IBFFA) model, which adopted a very efficient model-space trunction scheme, so no restriction needed to be made and complete calculations of the excitation energy spectra were obtained. We calculated a series of odd-odd isotopes, 176–184Re. The calculations started from even-even Os cores, where a simplified hamiltonian for the SU(3) limit in the IBA-1 model was used. Both negative-and positive-parity calculations for nearby odd-mass Re and Os isotopes have also been carried out. The detailed results of excitation energy spectra of all three types of calculations are presented, also some selected quadrupole and magnetic moments, and B(E2) and B(M1) values. All calculations are compared with experimental data. One of the successes of the IBFFA model is the prediction of the doubly-decoupled bands, which have been verified from experiments.