Publication: Lifetimes and shape-coexisting states of( 99)Zr
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2019-07-16
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American Physical Society
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Abstract
Lifetimes of intermediate-spin states in two rotational bands of Zr-99 have been measured. These states were populated following the neutron-induced fission of U-235 at the PF1B beamline of the Institut Laue-Langevin, Grenoble, during the EXILL-FATIMA campaign. The nucleus Zr-99(59) exhibits shape coexistence and lies precisely on the border of an abrupt change in ground-state deformation when going from N = 58 to N = 60, making its study interesting for understanding the mechanisms involved in the rapid onset of deformation here. The B(E2) values extracted for decays in the nu 3/2[541] band allow quadrupole deformations of beta(2) = 0.34(1) and 0.26(3) to be determined for the 821.6- and 1236.6-keV members, whereas beta(2) = 0.32(3) was found for the 850.5-keV member of the nu 3/2[411] band. Some of the excited states known in Zr-99 have been reasonably described with interacting boson-fermion model (IBFM) calculations. Type-II shell evolution is proposed to play a major role in modifying single-particle energies in Zr-99.
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Artículo firmado por 41 autores. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. This work was supported by NuPNET and the German BMBF by Grants No. 05P12PKNUF, No. 05P15RDFN1 and No. 05P12DRNUP, the German Research Council (DFG) under Grant No. SFB 1245, the Spanish MINECO via Project No. FPA2015-65035-P, the UK STFC by Contract No. DNC7RP01/4, the US DOE under Grant No. DE-FG02-91ER40609, and the UK National Measurement Office. The EXILL-FATIMA campaign would not have been possible without the support of several services at the ILL and the LPSC. We are grateful to the EXOGAM Collaboration for the loan of the detectors, to GANIL for assistance during installation and dismantling, and to the FATIMA Collaboration for the provision of LaBr3(Ce) detectors and analog electronics.