Isobarically purified beams of ${}^{77}\mathrm{Cu}$ with energies of $225$ and $0.2$ MeV were used at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory to study $\beta$ decay into states in ${}^{77}\mathrm{Zn}$. Data taken at $225$ MeV allowed the determination of absolute branching ratios relative to the decay of ${}^{77}\mathrm{Cu}$ for this $\beta$ decay as well as its daughters. From these we obtained a refined $\beta$-delayed neutron emission probability of $30.3(22)\%$ and a probability that the decay proceeds through ${}^{77}\mathrm{Zn}$${}^g$ of $49.1(26)\%$. A total of $64\hspace{0.5em}\gamma$ rays were placed in a level scheme for ${}^{77}\mathrm{Zn}$ containing $35$ excited states including one state above the neutron separation energy, whereas two $\gamma$ rays were observed for the $\beta$$n$ branch to states in ${}^{76}\mathrm{Zn}$. The growth and decay curves of some prominent $\gamma$ rays indicate a single $\beta$-decaying state with a half-life of $480(9)\hspace{0.5em}$ms. The decay pattern for ${}^{77}\mathrm{Cu}$, with observed feeding of $8(3)\%$ to $7/2^{+}\hspace{0.5em}$${}^{77}\mathrm{Zn}$${}^g$ and $6(3)\%$ to $1/2^{-}\hspace{0.5em}$${}^{77}\mathrm{Zn}$${}^m$, in contrast to the large feeding observed for decay of $\pi p_{3/2}$ ${}^{73}\mathrm{Cu}$${}^g$ to $1/2^{-}\hspace{0.5em}$${}^{73}\mathrm{Zn}$${}^g$, strongly suggests a $\pi f_{5/2}$ ground state for the studied ${}^{77}\mathrm{Cu}$ activity.

• Received 12 August 2009

DOI:https://doi.org/10.1103/PhysRevC.80.054304