Single-particle structures, high-spin isomers, and a strongly coupled band in odd-odd ${}^{120}\mathrm{Sb}$

Excited states in ${}^{120}\mathrm{Sb}$ have been investigated using the ${}^{116}\mathrm{Cd}({}^7\mathrm{Li},3n){}^{120}\mathrm{Sb}$ reaction at a beam energy of 34 MeV. A total of 15 new $\gamma$ rays were added into the level scheme of ${}^{120}\mathrm{Sb}$. Most of the observed single-particle states can be interpreted in terms of weak coupling of the odd proton and odd neutron to an excited ${}^{118}\mathrm{Sn}$ core involving either vibrational states or broken neutron pairs. The previously known strongly coupled rotational band based on the $\pi g_{9/2}^{-1}\otimes \nu h_{11/2}$ configuration has been extended up to the ${(15}^{-})$ state. The configuration-fixed constrained triaxial relativistic mean-field approaches and the particle rotor model are employed to discuss the high-spin isomers and strongly coupled rotational band, respectively.

Figure 1

Level scheme of ${}^{120}\mathrm{Sb}$ deduced from the present work. Transition energies are given in keV, and the widths of the arrows represent the relative intensities of the $\gamma$ transitions. The level energy of the 8${}^{-}$ isomeric state is set as 0. Newly observed transitions are indicated by asterisks and red lines.

Figure 2

Representative coincidence spectra gated by the (a) 230.4-keV transition, (b) 1242.5-keV transition, and (c) 178.9-keV transition.

Figure 3

Systematics of single-particle states in ${}^{118}\mathrm{Sn}$ [17] and ${}^{119}\mathrm{Sb}$ [12] compared to the corresponding states in ${}^{120}\mathrm{Sb}$.

Figure 4

Comparison of the single-particle levels in ${}^{120}\mathrm{Sb}$ with the corresponding levels in the ${}^{118}\mathrm{Sn}$ core nucleus. Levels connected by dashed lines are interpreted as the core states and the corresponding coupled states in terms of weak coupling. Experimental data and configuration assignments for ${}^{118}\mathrm{Sn}$ are taken from Refs. [17, 18, 19, 20].

Figure 5

Experimental $B\left(M1\right)/B\left(E2\right)$ ratios for the $\pi g_{9/2}^{-1}\otimes \nu h_{11/2}$ bands in the odd-odd isotopes ${}^{112}\mathrm{Sb}$ [8], ${}^{114}\mathrm{Sb}$ [11], ${}^{116}\mathrm{Sb}$ [4], ${}^{118}\mathrm{Sb}$ [2], and ${}^{120}\mathrm{Sb}$ (present work).

Figure 6

Calculated $B\left(M1\right)/B\left(E2\right)$ ratios for the $\pi g_{9/2}^{-1}\otimes \nu h_{11/2}$ configuration for different neutron Fermi levels in the $\nu h_{11/2}$ subshell. In the calculations, the odd proton is fixed to be a pure $g_{9/2}$ hole, whereas the odd neutron is treated as a BCS quasiparticle with ${\lambda }_n={\lambda }_1,{\lambda }_2,\cdots ,{\lambda }_6$, respectively.