Isospin structure of Jπ=1+ states in Ni58 and Cu58 studied by Ni58(p,p') and Ni58(He3,t)Cu58 measurements

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 Tz of the isospin T, where Tz=(N-Z)/2. The analogous structure has been studied for the isobaric nuclei Ni58 and Cu58 by comparing the transitions from the Ni58 ground state (initial isospin Ti=1 and Jπ=0+) to the M1 and the Gamow-Teller (GT) states (Jπ=1+) in Ni58 and Cu58, respectively. For this purpose, proton inelastic scattering (p,p') at Ep=160 MeV and the charge-exchange (He3,t) reaction at 140 MeV/nucleon were both measured at 0°, exciting final states with isospin Tf=1 and 2 and Tf=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 Tf=1 and 2 of analog GT and M1 states were identified. The distribution of Tf=2 states was also compared with results of Ni58(d,He2), Ni58(t,He3), and Ni58(n,p) experiments, in which only Tf=2 states are excited. The obtained GT strength distribution is compared with the results of shell-model calculations.