Monopole migration in 69,71,73Cu observed from β decay of laser-ionized 68-74Ni -: art. no. 054308

The neutron-rich isotopes Ni68-74 have been produced at the LISOL facility in the fission of U-238 induced by a 30-MeV proton beam. They have been extracted selectively through resonant laser ionization and electromagnetic mass separation. Production rates have been deduced and deviate from theoretical predictions. The beta decay of the isotopes has been investigated by means of beta-gamma and gamma-gamma spectroscopy. Half-lives have been determined for Ni68-74, and the level scheme has been extended for Cu-69 and newly established for Cu-71.73. The constructed schemes show an unexpected and sharp lowering of the pif(5/2) orbital with respect to the pip(3/2) ground state. This feature is ascribed to the monopole term of the residual proton-neutron interaction and is well reproduced by realistic shell-model calculations.