  The {\beta} decays of very neutron-rich nuclides in the Co-Zn region were
studied experimentally at the National Superconducting Cyclotron Laboratory
using the NSCL {\beta}-counting station in conjunction with the neutron
detector NERO. We measured the branchings for {\beta}-delayed neutron emission
(Pn values) for 74Co (18 +/- 15%) and 75-77Ni (10 +/- 2.8%, 14 +/- 3.6%, and 30
+/- 24%, respectively) for the first time, and remeasured the Pn values of
77-79Cu, 79,81Zn, and 82Ga. For 77-79Cu and for 81Zn we obtain significantly
larger Pn values compared to previous work. While the new half-lives for the Ni
isotopes from this experiment had been reported before, we present here in
addition the first half-life measurements of 75Co (30 +/- 11 ms) and 80Cu
(170+110 -50 ms). Our results are compared with theoretical predictions, and
their impact on various types of models for the astrophysical rapid
neutron-capture process (r-process) is explored. We find that with our new
data, the classical r-process model is better able to reproduce the A = 78-80
abundance pattern inferred from the solar abundances. The new data also
influence r-process models based on the neutrino-driven high-entropy winds in
core collapse supernovae.
