New Half-lives of r-process Zn and Ga Isotopes Measured with Electromagnetic Separation

The beta decays of neutron-rich nuclei near the doubly magic Ni-78 were studied at the Holifield Radioactive Ion Beam Facility using an electromagnetic isobar separator. The half-lives of Zn-82 (228 +/- 10 ms), Zn-83 (117 +/- 20 ms), and Ga-85 (93 +/- 7 ms) were determined for the first time. These half-lives were found to be very different from the predictions of the global model used in astrophysical simulations. A new calculation was developed using the density functional model, which properly reproduced the new experimental values. The robustness of the new model in the Ni-78 region allowed us to extrapolate data for more neutron-rich isotopes. The revised analysis of the rapid neutron capture process in low entropy environments with our new set of measured and calculated half-lives shows a significant redistribution of predicted isobaric abundances strengthening the yield of A > 140 nuclei.