Unambiguous Identification of Three $\beta$-Decaying Isomers in $^{70}$Cu
Résumé
Using resonant laser ionization, $\beta$-decay studies, and for the first time mass measurements, three $\beta$-decaying states have been unambiguously identified in $^{70}$Cu. A mass excess of –62 976.1(1.6) keV and a half-life of 44.5(2) s for the (6$^–$) ground state have been determined. The level energies of the (3$^–$) isomer at 101.1(3) keV with $T_{1/2}$ = 33(2) s and the 1$^+$ isomer at 242.4(3) keV with $T_{1/2}$ = 6.6(2) s are confirmed by high-precision mass measurements. The low-lying levels of $^{70}$Cu populated in the decay of $^{70}$Ni and in transfer reactions compare well with large-scale shell-model calculations, and the wave functions appear to be dominated by one proton–one neutron configurations outside the closed Z = 28 shell and N = 40 subshell. This does not apply to the 1$^+$ state at 1980 keV which exhibits a particular feeding and deexcitation pattern not reproduced by the shell-model calculations.