Localizing the Shape Transition in Neutron-Deficient Selenium

Journal Article · 21 August 2018 · Physical Review Letters

DOI: https://doi.org/10.1103/PhysRevLett.121.082502 · OSTI ID:1466655

Henderson, J. ^[1]; Wu, C. Y. ^[2]; Ash, J. ^[3]; Bender, P. C. ^[4]; Elman, B. ^[3]; Gade, A. ^[3]; Grinder, M. ^[3]; Iwasaki, H. ^[3]; Kwan, E. ^[5]; Longfellow, B. ^[3]; Mijatović, T. ^[5]; Rhodes, D. ^[3]; Spieker, M. ^[5]; Weisshaar, D. ^[5]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); NSCL at Michigan State University
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
3. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab. and Dept. of Physics and Astronomy
4. Univ. of Massachusetts, Lowell, MA (United States). Dept. of Physics and Applied Physics
5. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.

Neutron-deficient selenium isotopes are thought to undergo a rapid shape change from a prolate deformation near the line of beta stability towards oblate deformation around the line of $N=Z$. The point at which this shape change occurs is unknown, with inconsistent predictions from available theoretical models. A common feature in the models is the delicate nature of the point of transition, with the introduction of even a modest spin to the system sufficient to change the ordering of the prolate and oblate configurations. In this paper, we present a measurement of the quadrupole moment of the first-excited state in radioactive $$^{72}\mathrm{Se}$$—a potential point of transition—by safe Coulomb excitation. This is the first low-energy Coulomb excitation to be performed with a rare-isotope beam at the reaccelerated beam facility at the National Superconducting Cyclotron Laboratory. Finally, by demonstrating a negative spectroscopic quadrupole moment for the first-excited $${2}^{+}$$ state, it is found that any low-spin shape change in neutron-deficient selenium does not occur until $$^{70}\mathrm{Se}$$.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Michigan State Univ., East Lansing, MI (United States)
• Sponsoring Organization: National Science Foundation (NSF) (United States); USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation (NA-20); USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• Grant/Contract Number: AC52-07NA27344; FG02-08ER41556; NA0003180
• OSTI ID: 1466655
• Report Number(s): LLNL-JRNL--750400
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 8 Vol. 121; ISSN 0031-9007
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English