Abstract
Isobarically purified beams of 77Cu with energies of 225 and 0.2 MeV were used at the
Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory to study β
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 β decay as well as its daughters.
From these we obtained a refined β-delayed neutron emission probability of 30.3(22)%
and a probability that the decay proceeds through 77Zng of 49.1(26)%. A total of 64 γ
rays were placed in a level scheme for 77Zn containing 35 excited states including one
state above the neutron separation energy, whereas two γ rays were observed for the
βn branch to states in 76Zn. The growth and decay curves of some prominent γ rays
indicate a single β-decaying state with a half-life of 480(9) ms. The decay pattern for
77Cu, with observed feeding of 8(3)% to 7/2+ 77Zng and 6(3)% to 1/2- 77Znm, in contrast to the large feeding observed for decay of πp3/2 73Cug to 1/2- 73Zng, strongly suggests a
πf5/2 ground state for the studied 77Cu activity.
