Gamow-Teller transitions from high-spin isomers in $\mathit{N}=\mathit{Z}$ nuclei

Gamow-Teller (GT) transitions from high-spin isomers are studied using the sum-rule approach and the shell model. The GT transition strengths from the high-spin isomeric states show a stronger collectivity than those from the ground states in two $N=Z$ nuclei ${}^{52}\mathrm{Fe}$ and ${}^{94}\mathrm{Ag}$. It is argued that the spin-up and spin-down Fermi spheres involved in the GT transitions from the high-spin isomeric states play important roles. These Fermi spheres are analogous to the isospin-up and isospin-down Fermi spheres for the GT transitions from the ground states in $N>Z$ nuclei and create a strong collectivity.

Figure 1

(Upper) GT transition strength distributions from the high-spin isomeric state $I^{\pi }={12}^{+}$ in ${}^{52}\mathrm{Fe}$ calculated by the shell model in the full $pf$-shell-model space with the GXPF1J [17] effective interaction. Transition strengths are averaged by a Lorentzian weighting function with a width of 0.5 MeV. Excitation energy is defined from the ground state of the daughter nucleus ${}^{52}\mathrm{Co}$. No quenching factor is adopted here. (Lower) The same as the upper panel but for the GT transition strength distributions from the ground-state $I^{\pi }=0^{+}$ in ${}^{52}\mathrm{Fe}$.

Figure 2

(Upper) GT transition strength distributions from the high-spin isomeric state $I^{\pi }={21}^{+}$ in ${}^{94}\mathrm{Ag}$ calculated by the shell model in the $(2p_{1/2},1g_{9/2},1g_{7/2},2d_{5/2})$-shell-model space with a modified P1GD5G3 [18] effective interaction. Transition strengths are averaged by a Lorentzian weighting function with a width of 0.5 MeV. Excitation energy is defined from the ground state of the daughter nucleus ${}^{94}\mathrm{Cd}$. No quenching factor is adopted here. (Lower) The same as the top panel but for the GT transition strength distributions from the ground-state $I^{\pi }=0^{+}$ in ${}^{94}\mathrm{Ag}$.