Isospin structure of ${J}^{\ensuremath{\pi}}={1}^{+}$ states in $^{58}\mathrm{Ni}$ and $^{58}\mathrm{Cu}$ studied by $^{58}\mathrm{Ni}$($p,{p}^{'}$) and $^{58}\mathrm{Ni}$($^{3}\mathrm{He}$,$t$)$^{58}\mathrm{Cu}$ measurements

Isospin structure of $J^{π} = 1^{+}$ states in ${}^{58}{Ni}$ and ${}^{58}{Cu}$ studied by ${}^{58}{Ni}$ ( $p, p^{'}$ ) and ${}^{58}{Ni}$ ( ${}^{3}{He}$ , $t$ ) ${}^{58}{Cu}$ measurements

H. Fujita et al.

Phys. Rev. C 75, 034310 – Published 21 March 2007

Abstract

Isospin is a good quantum number under the assumption that the nuclear interaction is charge independent. An analogous structure of excited states is expected for nuclei with the same mass number $A$ but with different $z$ components $T_{z}$ of the isospin $T$ , where $T_{z} = (N - Z) / 2$ . The analogous structure has been studied for the isobaric nuclei ${}^{58}{Ni}$ and ${}^{58}{Cu}$ by comparing the transitions from the ${}^{58}{Ni}$ ground state (initial isospin $T_{i} = 1$ and $J^{π} = 0^{+}$ ) to the $M 1$ and the Gamow-Teller (GT) states ( $J^{π} = 1^{+}$ ) in ${}^{58}{Ni}$ and ${}^{58}{Cu}$ , respectively. For this purpose, proton inelastic scattering ( $p, p^{'}$ ) at $E_{p} = 160$ MeV and the charge-exchange ( ${}^{3}{He}$ , $t$ ) reaction at 140 MeV/nucleon were both measured at $0^{°}$ , exciting final states with isospin $T_{f} = 1$ and 2 and $T_{f} = 0$ , 1, and 2, respectively. High energy and scattering-angle resolutions were achieved by applying complete beam matching techniques. On the basis of the correspondence between excitation energies and transition strengths, isospin values $T_{f} = 1$ and 2 of analog GT and $M 1$ states were identified. The distribution of $T_{f} = 2$ states was also compared with results of ${}^{58}{Ni}$ ( $d,$ ${}^{2}{He}$ ), ${}^{58}{Ni}$ ( $t,$ ${}^{3}{He}$ ), and ${}^{58}{Ni}$ ( $n, p$ ) experiments, in which only $T_{f} = 2$ states are excited. The obtained GT strength distribution is compared with the results of shell-model calculations.