Microsecond and nanosecond isomers populated in fission reactions
- Dept. of Physics, School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7HX (United Kingdom)
- Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)
- Dept. of Physics and Astronomy, Youngstown State University, Youngstown, Ohio 44555 (United States)
- TRIUMF, 4004 Westbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada)
- University of Massachusetts Lowell, Lowell, MA 01854 (United States)
- Dept. of Nuclear Physics, RSPhysSE, Australian National University, Canberra 0200 (Australia)
Fusion-fission reactions were induced by bombarding a thick 27Al target with 178Hf projectiles at a laboratory energy of 1150 MeV using the ATLAS accelerator at Argonne National Laboratory. The subsequent {gamma}-ray decays were measured using the GAMMASPHERE germanium detector array. The beam was pulsed at two different ON/OFF cycles of 82.5/825 ns and 25/75 {mu}s in order to observe the {gamma} rays from the decay of isomeric states. In 121Sb 2721+{delta} keV, I{pi}=(25/2+) and 2434 keV, I{pi}=19/2- states have measured half-lives of T1/2=200(30) {mu}s and 8.2(2) ns respectively. The 2614+{delta} keV, I{pi}=(27/2+) and 2486 keV, I{pi}=19/2+ states in 123Sb have measured half-lives of T1/2=52(3) {mu}s and 7.9(4) ns respectively. The positive parity isomers in these nuclei correspond to a {pi}d5/2 or {pi}g7/2 configuration, in 121Sb and 123Sb respectively, coupled to aligned (h11/2)2 neutrons. The I{pi}=19/2- isomeric state in 121Sb is proposed to have a {nu}h11/2 x {nu}d3/2 x {pi}d5/2 configuration. A previously unobserved isomer has been identified in 99Mo at an energy of 3010 keV, decaying with T1/2=18(5) ns. This state is interpreted as an energetically favoured 3 quasi-particle alignment of {nu} ({sub d{sub 5/2}} {sup g{sub 7/2}}) x {pi}(g{sub 9/2}){sup 2} configuration which is observed systematically in the even-Z N=57 isotones.
- OSTI ID:
- 20888159
- Journal Information:
- AIP Conference Proceedings, Vol. 853, Issue 1; Conference: FUSION06: International conference on reaction mechanisms and nuclear structure at the Coulomb barrier, Venice (Italy), 19-23 Mar 2006; Other Information: DOI: 10.1063/1.2338400; (c) 2006 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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