Large β-Delayed Neutron Emission Probabilities in the 78Ni Region...

The β-delayed neutron branching ratios (Pβn) for nuclei near doubly magic 78Ni have
been directly measured using a new method combining high-resolution mass
separation, reacceleration, and digital β-γ spectroscopy of 238U fission products. The Pβn
values for the very neutron-rich isotopes 76–78Cu and 83Ga were found to be much
higher than previously reported and predicted. Revised calculations of the βn process,
accounting for new mass measurements and an inversion of the π2p3/2 and π1f5/2
orbitals, are in better agreement with these new experimental results.