Influence of triaxiality on the signature inversion in odd-odd nuclei

Complete text of publication follows. Signature inversion in the A ∼ 100 region has been reported earlier only in the case of the odd-odd 98Rh nucleus. Our studies on the 100-103Rh isotopes and a close inspection of the known πg9/2νh11/2 bands of the Rh (Z = 45) and Ag (Z = 47) isotopes revealed that the signature splitting effects, earlier considered as quenchings of signature splitting, are not only quenchings but signature inversions. Indeed, the energetically favored signature at low spins in these πg9/2νh11/2 bands is the α = 1 branch (odd spins) instead of the expected α = 0 branch (even spins). The systematic occurrence of signature inversion in this mass region is discussed in Refs. together with attempts to understand its behavior qualitatively. Among many attempts for interpreting the mechanism of signature inversion in odd-odd nuclei, a model using an axially symmetric rotor plus two quasi-particles has already been successfully applied to describe the observed signature inversions in the A ∼ 80 and A ∼ 160 mass regions. According to this model the signature inversion is caused by the competition between the Coriolis and the proton-neutron residual interactions in low K space. Such calculations have been also successfully applied to the πg9/2νh11/2 bands in the odd-odd 98Rh and 102Rh nuclei. Recent observations of chiral band structures in the nearby Rh nuclei suggest a possibility of triaxiality in these nuclei, too. In the present work we examined the possible influence of triaxiality on the signature inversion using a triaxial rotor plus two-quasiparticle model and compared the results with the experimental data of 98Rh and 102Rh. The calculations provided a better agreement with the experiment than the axially symmetric calculations. Compared to the axially symmetric case, the triaxiality applied in the Hamiltonian enlarges the amplitudes of high-spin signature zigzags at small triaxial deformation and might push the signature inversion point to higher spin at large triaxial deformation. The results are published in Ref. (author)