Mass Measurements beyond the Major r-Process Waiting Point 80Zn

High-precision mass measurements on neutron-rich zinc isotopes Zn-71m,Zn-72-81 have been performed with the Penning trap mass spectrometer ISOLTRAP. For the first time, the mass of Zn-81 has been experimentally determined. This makes Zn-80 the first of the few major waiting points along the path of the astrophysical rapid neutron-capture process where neutron-separation energy and neutron-capture Q-value are determined experimentally. The astrophysical conditions required for this waiting point and its associated abundance signatures to occur in r-process models can now be mapped precisely. The measurements also confirm the robustness of the N=50 shell closure for Z=30.