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Title: Observation of excited states in 20Mg sheds light on nuclear forces and shell evolution

Journal Article · · Physical Review C
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  1. Saint Mary’s Univ., Halifax, Nova Scotia (Canada). Astronomy and Physics Dept.; TRIUMF, Vancouver, BC (Canada)
  2. TRIUMF, Vancouver, BC (Canada)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Physics Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Physics Division, and National Center for Computational Sciences
  5. Simon Fraser Univ., Burnaby, British Columbia (Canada). Dept. of Chemistry
  6. Saint Mary’s Univ., Halifax, Nova Scotia (Canada). Astronomy and Physics Dept.
  7. Univ. of Guelph, Guelph, Ontario (Canada). Dept. of Physics
  8. McMaster Univ., Hamilton, ON (Canada). Dept. of Physics and Astronomy
  9. TRIUMF, Vancouver, BC (Canada); Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Physics
  10. High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)
  11. Saint Mary’s Univ., Halifax, Nova Scotia (Canada). Astronomy and Physics Dept.; Dalhousie Univ., Halifax, Nova Scotia (Canada). Dept. of Physics and Atmospheric Science
  12. TRIUMF, Vancouver, BC (Canada); Univ. of British Columbia, Vancouver, BC (Canada). Dept. of Physics and Astronomy
  13. National Autonomous Univ. of Mexico, Mexico City (Mexico). Inst. of Nuclear Sciences
  14. Univ. of Edinburgh, Scotland (United Kingdom)
  15. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  16. TRIUMF, Vancouver, BC (Canada); Univ. of York (United Kingdom). Dept. of Physics
+ Show Author Affiliations

The exotic Borromean nucleus 20Mg with N = 8, located at the proton drip line provides a unique testing ground for nuclear forces and the evolution of shell structure in the neutron-deficient region. We report on the first observation of proton unbound resonances together with bound states in 20 Mg from the 20Mg (d, d ') reaction performed at TRIUMF. Phenomenological shell-model calculations offer a reasonable description. However, our experimental results present a challenge for current first-principles nuclear structure approaches and point to the need for improved chiral forces and ab initio calculations. Furthermore, the differential cross section of the first excited state is compared with distorted-wave Born approximation calculations to deduce a neutron quadrupole deformation parameter of β$$_n$$ = 0.46 ± 0.21 . Lastly, this provides the first indication of a possible weakening of the N = 8 shell closure at the proton drip line.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Organization:
DOE Office of Science; USDOE; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Grant/Contract Number:
AC05-00OR22725; AC52-07NA27344; SC0018223
OSTI ID:
1502031
Report Number(s):
LLNL-JRNL--754342; 940603
Journal Information:
Physical Review C, Journal Name: Physical Review C Journal Issue: 2 Vol. 99; ISSN PRVCAN; ISSN 2469-9985
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (1)

Description of proton-rich nuclei in the A ≈ 20 region within the Gamow shell model journal December 2019

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS