β decay of 72Co and microsecond isomers in even-mass neutron-rich nickel isotopes

A new excited state at 2164 keV has been identified in Ni-72 with tentative spin and parity of 4(+) based on comparison to shell model calculations. This level is suggested to be populated via the beta-decay of an isomeric state in Co-72, and is postulated to be one of the key states that play a role in the disappearance of isomers in Ni-72,Ni-74. The known low-energy levels in Ni-72 are compared with results of shell model calculations using the NR78 interaction to follow the seniority of the observed states. In addition, the half-life of the 8(+) isomer in Ni-76 has been measured as 630(90) ns and the full cascade of transitions from this isomer has been verified experimentally in this work.