β decay of 66Co, 68Co, and 70Co -: art. no. 054308

The neutron-rich nuclei, Co-66, Co-68, and Co-70 were produced using a laser-ionization isotope-separation on-line method. The resulting beta-delayed gamma decay was studied. The half-life of Co-66 is measured to be 0.18(1) s. Two beta-decaying states are identified in Co-68 With half-lives of 0.23(3) and 1.6(3) s. In addition, two beta-decaying states are observed in Co-70 With half-lives of 0.12(3) and 0.50(18) s. From the beta decay of these states in Co-66,Co-68,Co-70, many new excited levels are established in Ni-66, Ni-68, and Ni-70. These results are compared to the valence mirror nuclei in the N=50 region as well as with shell-model calculations. It can be concluded that collective excitations appear to play an increasingly important role with increasing occupation of the nu g(9/2), orbital.