Decays of New Nuclides and Isomers Beyond the Proton Drip Line--The Influence of Neutron Configurations
- Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE (United Kingdom)
- STFC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD (United Kingdom)
- Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom)
- Department of Physics, University of Jyvaeskylae, FIN-40014, Jyvaeskylae (Finland)
The energy of the vh{sub 9/2} orbital in nuclei above N = 82 drops rapidly in energy relative to the vf{sub 7/2} orbital as the occupancy of the {pi}h{sub 11/2} orbital increases. These two neutron orbitals become nearly degenerate as the proton drip line is approached. In this work, we have discovered the new nuclides {sup 161}Os and {sup 157}W, and studied the decays of the proton emitter {sup 160}Re in detail. The {sup 161}Os and {sup 160}Re nuclei were produced in reactions of 290, 300 and 310 MeV {sup 58}Ni ions with an isotopically enriched {sup 106}Cd target, separated in-flight using the RITU separator and implanted into the GREAT spectrometer. The {sup 161}Os{alpha} a decays populated the new nuclide {sup 157}W, which decayed by {beta}-particle emission. The {beta} decay fed the known {alpha}-decaying 1/2{sup +} and 11/2{sup -} states in {sup 157}Ta, which is consistent with a vf{sub 7/2} ground state in {sup 157}W. The measured {alpha}-decay energy and half-life for {sup 161}Os correspond to a reduced {alpha}-decay width that is compatible with s-wave {alpha}-particle emission, implying that its ground state is also a vf{sub 7/2} state. Over 7000 {sup 160}Re nuclei were produced and the {gamma} decays of a new isomeric state feeding the {pi}d{sub 3/2} level in {sup 160}Re were discovered, but no evidence for the proton or a decay of the expected {pi}h{sub 11/2} state could be found. The isomer decays offer a natural explanation for this non-observation and provides a striking example of the influence of the near degeneracy of the vh{sub 9/2} and vf{sub 7/2} orbitals on the properties of nuclei in this region.
- OSTI ID:
- 21254799
- Journal Information:
- AIP Conference Proceedings, Vol. 1072, Issue 1; Conference: International conference on nuclear physics and astrophysics: From stable beams to exotic nuclei, Cappadocia (Turkey), 25-30 Jun 2008; Other Information: DOI: 10.1063/1.3039824; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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