Prompt and delayed γ spectroscopy of neutron-rich Kr-94 and observation of a new isomer

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Amer Physical Soc
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Prompt and delayed gamma-ray spectroscopy of the neutron-rich Kr-94 was performed, as part of the fission campaign at the ALTO facility of the IPN Orsay, using the fast-neutron-induced fission reaction U-238(n, f) in combination with the nu-Ball array, a novel hybrid gamma spectrometer for energy and lifetime measurements. Several new yrast and nonyrast transitions were observed for the first time, extending the previously known level scheme. Additionally, we report on the observation of a new short-lived isomer at 3444 keV with a half-life of 32(3) ns. The analysis of the Nilsson orbitals obtained from Gogny cranked Hartree-Fock-Bogoliubov calculations suggests a (9(-)) spin and an oblate deformation for this isomer corresponding to a two-quasineutron state, indicating an isomeric structure very similar to that of the neighboring isotones Sr-96 and Se-92.
©2020 American Physical Society. Artículo firmado por 75 autores. We thank the accelerator staff of the ALTO facility at the IPN Orsay for providing a stable beam and continuous support. This work is supported by the Deutsche Forschungsgemeinschaft (DFG) under Grant No. BL 1513/1-1 and by the BMBF under Grants No. 05P15RDFN1 and No. 05P19RDFN1. This work was partially funded by the Spanish government via Projects FPA2015-65035-P and RTI2018-09886 8-B-I00. This work was partially supported by the STFC UK Nuclear Data Network, the STFC (Grants No. ST/L005743/1 and No. ST/P005314), the University of Surrey Marion Redfearn Trust. A.B., M.B., P.I., S.J., and P.H.R. acknowledge support from the UK Department of Business, Energy and Industrial Strategy (BEIS) via the National Measurement System. This work was supported by EC funding for External Research Teams within the HORIZON2020 Program of the European Commission TransNational Access to ALTO under the Integrated Infrastructure Initiative European Nuclear Science and Applications Research 2 (ENSAR2) Grant Agreement No. 654002. The use of germanium detectors from the GAMMAPOOL is acknowledged.
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