Direct measurement of beta-delayed neutron emission for Cobalt Isotopes using VANDLE

Cobalt (Z=27) decays to Nickel (Z=28). Z=28 is a proton magic number. Beta-delayed neutron emission requires decay to above the neutron separation energy of the Nickel beta-daughter. In Cobalt decays, this is achieved through "proton core breaking." Where instead of populating the proton f7/2 orbital from the neutron transition to a proton, the excited proton p3/2 is populated instead. The strength above the neutron separation energy is dependent on the proton shellgap above f7/2 and the neutron shellgap above p1/2, as neutron-rich Cobalt isotopes populate the neutron g9/2 orbital. This is compared to observations of Co-70gs,70m,71,72,73,74,75 from experiments at NSCL and RIKEN, both utilizing VANDLE arrays. The distribution of states above the neutron separation energy of the beta-daughter that undergo neutron emission is modeled by a combination of shell model and statistical model calculations.