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Multistep Coulomb excitation of Ni 64 : Shape coexistence and nature of low-spin excitations

Journal Article · · Physical Review. C
 [1];  [2];  [2];  [3];  [4];  [5];  [6];  [7];  [6];  [8];  [7];  [7];  [7];  [7];  [7];  [9];  [9];  [10];  [10];  [11] more »;  [12] « less
  1. Univ. of North Carolina, Chapel Hill, NC (United States); Duke Univ., Durham, NC (United States); Michigan State University
  2. Univ. of North Carolina, Chapel Hill, NC (United States); Duke Univ., Durham, NC (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Univ. of Tsukuba, Ibaraki (Japan); Univ. of Tokyo (Japan)
  5. Univ. of Tokyo (Japan); RIKEN Nishina Center, Saitama (Japan); KU Leuven (Belgium)
  6. Michigan State Univ., East Lansing, MI (United States)
  7. Argonne National Lab. (ANL), Argonne, IL (United States)
  8. Michigan State Univ., East Lansing, MI (United States); TRIUMF, Vancouver, BC (Canada)
  9. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  10. Univ. of Massachusetts, Lowell, MA (United States)
  11. Univ. of Maryland, College Park, MD (United States); Georgia Tech Research Inst., Atlanta, GA (United States)
  12. Univ. of Maryland, College Park, MD (United States)
+ Show Author Affiliations
Here, the structure of 64Ni, the heaviest stable Ni isotope, has been investigated via high-statistics, multistep safe Coulomb excitation to search for shape coexistence, a phenomenon recently observed in neutron-rich 66Ni and 70Ni as well as in doubly magic, N = 40, 68Ni. The study was motivated by recent, state-of-the-art Monte Carlo shell-model calculations (MCSM), where a Hamiltonian with effective interactions incorporating the monopole tensor force predicts the existence of shape coexistence, also in the lower-mass 62,64Ni isotopes. A set of transition and static E2 matrix elements for both yrast and near-yrast structures was extracted from the differential Coulomb excitation cross sections. From comparisons between the new results and MCSM as well as other shell-model calculations, a clearer picture of the structure of 64Ni emerges. Specifically, the low-spin states are shown to be dominated by proton and neutron excitations mainly within the fp shell, with minimal contribution from the g9/2 shape-driving neutron orbital. The agreement between experimental data and MCSM results indicates a small oblate deformation for the $$0$$$^{+}_{2}$$ level and a spherical shape for the $$0$$$^{+}_{3}$$ state. In addition, the small upper limit determined for the B(E2) probability of a transition associated with the decay of the recently observed 3463-keV, $$0$$$^{+}_{4}$$ state agrees with its proposed assignment to a prolate shape, herewith providing first evidence for triple shape coexistence in a stable Ni isotope.
Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Michigan State Univ., East Lansing, MI (United States); Univ. of North Carolina, Chapel Hill, NC (United States)
Sponsoring Organization:
Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan; National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
AC02-05CH11231; AC02-06CH11357; AC52-07NA27344; FG02-08ER41556; FG02-94ER40848; FG02-97ER41033; FG02-97ER41041; SC0020451
OSTI ID:
1892378
Alternate ID(s):
OSTI ID: 1893589
OSTI ID: 1895050
OSTI ID: 1908106
Report Number(s):
LLNL-JRNL-835854
Journal Information:
Physical Review. C, Journal Name: Physical Review. C Journal Issue: 4 Vol. 106; ISSN 2469-9985
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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