  High-precision mass measurements on neutron-rich zinc isotopes 71m,72-81Zn
have been performed with the Penning trap mass spectrometer ISOLTRAP. For the
first time the mass of 81Zn has been experimentally determined. This makes 80Zn
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. As a consequence, 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 farther from stability.
