Monday, Dec 12, 2016, 2:00 PM, 385E
Miguel Madurga, (Joint Institute for Nuclear Physics and Applications / University of Tennessee)
The role of beta-decay in the synthesis of elements in dying stars

About half of all atomic elements heavier than iron are produced in the particular conditions occurring during stellar death. In the rapid neutron capture process, or r-process, neutrons from the stellar environment are quickly absorbed by stable nuclei. The isotopes produced in these conditions have neutron-proton imbalances much larger than stable matter, with properties that can be difficult to predict. In particular, systematic deviations from theoretical models have been observed in their beta-decay half-lives. In this colloquium I will review my recent experimental and theoretical efforts to develop a new model of beta-decay for key r-process nuclei, called waiting points. It will be shown that, unexpectedly, the nuclear orbital structure favors neutron over gamma emission in 83,84Ga, resulting in shorter half-lives when compared to calculations using a global model of the nucleus. This effect is found to explain the beta-decay half-life discrepancies with global models for all r-process waiting points beyond neutron magic numbers.