Abstract
Background: Nuclear structure plays a significant role on the rapid neutron capture process ( process) since shapes evolve with the emergence of shells and subshells. There was some indication in neighboring nuclei that we might find examples of a new subshell, which may give rise to a doubly magic Se nucleus.
Purpose: -decay half-lives of nuclei around Se have been measured to determine if this nucleus has in fact a doubly magic character.
Method: The fragmentation of a Xe beam at the National Superconducting Cyclotron Laboratory at Michigan State University was used to create a cocktail of nuclei in the region.
Results: We have measured the half-lives of 22 nuclei near the -process path in the region. The half-lives of As and Se have been measured for the first time. The values were compared with theoretical predictions in the search for nuclear-deformation signatures of a subshell, and its possible role in the emergence of a potential doubly magic Se. The impact of such hypothesis on the synthesis of heavy nuclei, particularly in the production of Sr, Y, and Zr elements was investigated with a weak -process network.
Conclusions: The new half-lives agree with results obtained from a standard global QRPA model used in -process calculations, indicating that Se has a quadrupole shape incompatible with a closed subshell in this region. The impact of the measured Se half-life in comparison with a former theoretical predication associated with a spherical half-life on the weak process is shown to be strong.
- Received 22 December 2011
DOI:https://doi.org/10.1103/PhysRevC.85.035807
©2012 American Physical Society