Accepted Wednesday Oct 21, 2009
Isobarically purified beams of 77Cu with energies of 225 MeV and 0.2 MeV have been used at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory to study b decay into states in 77Zn. Data taken at 225 MeV allowed the determination of absolute branching ratios relative to the decay of 77Cu for this decay as well as its daughters. From these we obtained a refined b-delayed neutron emission probability of 30.3(22)% and a probability that the decay proceeds through the 77Zng of 49.1(26)%. A total of 64 g rays were placed in a level scheme for 77Zn containing 35 excited states including one state above the neutron separation energy, while two g rays are observed for the b-n branch to states in 76Zn. The growth and decay curves of some prominent g rays indicate a single b decaying state with a half-life of 480(9) ms. The decay pattern for 77Cu, with observed feeding of 8(3)% to the 7/2+ 77Zng and 6(3)% to the 1/2- 77Znm in contrast to the large feeding observed for decay of the pp3/2 73Cug to the 1/2- 73Zng, strongly suggests a pf5/2 ground state for the studied 77Cu activity.