Abstract
Background: The evolution of nuclear shell structure far from stability can be explored by identifying and measuring the properties of isomers. Neutron-rich nuclei between the and the closed shells have been the subject of recent studies which have identified a number of isomers and measured detailed spectroscopic properties.
Purpose: The purpose of this analysis was to identify and measure the properties of short-lived isomeric states populated following decay in nuclei near the doubly magic nucleus .
Methods: Radioactive ions produced by beam fragmentation at the National Superconducting Cyclotron Laboratory were implanted into a scintillator coupled to a pixelated photomultiplier tube. Ancillary arrays of HPGe clover and detectors were positioned around the implantation detector to measure -delayed rays.
Results: The previously observed 2634-keV level in , populated following the decay of , was identified as isomeric with a half-life of 25.4(4) ns. A combination of timing and -ray spectroscopy was used to confirm this assignment. Shell-model calculations were performed and indicate that this state may be a negative-parity state formed by the occupation of the orbital.
Conclusions: A new isomeric state in has been identified, and its half-life was measured. Ambiguity about the structure of this state could be resolved with further experiments.
5 More- Received 19 July 2021
- Accepted 7 October 2021
DOI:https://doi.org/10.1103/PhysRevC.104.054314
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