Spectroscopy of odd-odd nuclei within the interacting boson-fermion-fermion model based on the Gogny energy-density functional

We present a method to calculate spectroscopic properties of odd-odd nuclei within the framework of the interacting boson-fermion-fermion model (IBFFM) based on the Gogny energy-density functional. The $(\beta ,\gamma )$-deformation energy surface of the even-even (boson-)core nucleus, spherical single-particle energies, and occupation probabilities of the odd neutron and odd proton are provided by the constrained self-consistent mean-field calculation within the Hartree-Fock-Bogoliubov method with the Gogny-D1M functional. These quantities are used as a microscopic input to fix most of the parameters of the IBFFM Hamiltonian. Only a few coupling constants for the boson-fermion Hamiltonian and the residual neutron-proton interaction are specifically adjusted to reproduce experimental low-energy spectra in odd-mass and odd-odd nuclei, respectively. In this way, the number of free parameters involved in the IBFFM framework is reduced significantly. The method is successfully applied to the description of the low-energy spectra and electromagnetic transition rates in the odd-odd ${}^{194,196,198}\mathrm{Au}$ nuclei.

Figure 1

The Gogny-D1M HFB and mapped IBM-2 energy surfaces in the $(\beta ,\gamma )$-deformation space for the ${}^{196–200}\mathrm{Hg}$ nuclei are plotted up to 5 MeV from the global minimum. The energy difference between the neighboring contours is 250 keV. The global minimum is indicated by a filled square.

Figure 2

Theoretical and experimental low-energy excitation spectra for the even-even nuclei ${}^{196,198,200}\mathrm{Hg}$. The experimental values are taken from the NNDC compilation [53].

Figure 3

Same as Fig. 2, but for the odd-$N$ nuclei ${}^{195,197,199}\mathrm{Hg}$.

Figure 4

Same as Fig. 2, but for the odd-$Z$ nuclei ${}^{195,197,199}\mathrm{Au}$.

Figure 5

Same as Fig. 2, but for the odd-odd nuclei ${}^{194,196,198}\mathrm{Au}$. The experimental values are taken from Refs. [53, 54] (for ${}^{194}\mathrm{Au}$), [53, 55] (for ${}^{196}\mathrm{Au}$), and [53] (for ${}^{198}\mathrm{Au}$).