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Publication

Masses and beta-Decay Spectroscopy of Neutron-Rich Odd-Odd Eu-160,Eu- 162 Nuclei: Evidence for a Subshell Gap with Large Deformation at N=98

Authors

Hartley, D. J.; Kondev, F. G.; Orford, R.; Clark, J. A.; Savard, G.; Ayangeakaa, A. D.; Bottoni, S.; Buchinger, F.; Burkey, M.; Carpenter, M. P.; Copp, P.; Hoffman, C. R.; Janssens, R. V. F. ; Klimes, J.; Lauritsen, T.; Seweryniak, D.; Zhu, S.

Abstract

The structure of deformed neutron-rich nuclei in the rare-earth region is of significant interest for both the astrophysics and nuclear structure fields. At present, a complete explanation for the observed peak in the elemental abundances at A similar to 160 eludes astrophysicists, and models depend on accurate quantities, such as masses, lifetimes, and branching ratios of deformed neutron-rich nuclei in this region. Unusual nuclear structure effects are also observed, such as the unexpectedly low energies of the first 2(+) levels in some even-even nuclei at N = 98. In order to address these issues, mass and beta-decay spectroscopy measurements of the Eu-160(97) and Eu-162(99) nuclei were performed at the Californium Rare Isotope Breeder Upgrade radioactive beam facility at Argonne National Laboratory. Evidence for a gap in the single-particle neutron energies at N = 98 and for large deformation (beta(2) similar to 0.3) is discussed in relation to the unusual phenomena observed at this neutron number.