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Title: First Application of Mass Measurements with the Rare-RI Ring Reveals the Solar r -Process Abundance Trend at A = 122 and A = 123

Journal Article · · Physical Review Letters
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  1. Chinese Academy of Sciences (CAS) (China); Lanzhou Univ. (China); RIKEN Nishina Center for Accelerator-Based Science (Japan); University of Chinese Academy of Sciences, Beijing (China)
  2. RIKEN Nishina Center for Accelerator-Based Science (Japan)
  3. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
  4. RIKEN Nishina Center for Accelerator-Based Science (Japan); Kyushu Univ., Fukuoka (Japan)
  5. RIKEN Nishina Center for Accelerator-Based Science (Japan); Japan Atomic Energy Agency (JAEA) (Japan)
  6. Saitama Univ. (Japan)
  7. Univ. of Tsukuba (Japan)
  8. Univ. of Tsukuba (Japan); RIKEN Nishina Center for Accelerator-Based Science (Japan)
  9. Univ. of Tokyo (Japan); Osaka Univ. (Japan)
  10. Univ. of Tokyo (Japan)
  11. RIKEN Nishina Center for Accelerator-Based Science (Japan); Institute for Basic Science (IBS), Daejeon (Korea, Republic of)
  12. Chinese Academy of Sciences (CAS) (China)
  13. Chinese Academy of Sciences (CAS) (China); GSI-Helmholtzzentrum fur Schwerionenforschung, Darmstadt (Germany)
  14. GSI-Helmholtzzentrum fur Schwerionenforschung, Darmstadt (Germany)
  15. National Physical Lab., Teddington (United Kingdom); Univ. of Surrey, Guildford (United Kingdom)
  16. Univ. of Surrey, Guildford (United Kingdom)
+ Show Author Affiliations

The Rare-RI Ring (R3) is a recently commissioned cyclotronlike storage ring mass spectrometer dedicated to mass measurements of exotic nuclei far from stability at Radioactive Isotope Beam Factory (RIBF) in RIKEN. The first application of mass measurement using the R3 mass spectrometer at RIBF is reported. Rare isotopes produced at RIBF—127Sn, 126In, 125Cd, 124Ag, 123Pd—were injected in R3. Masses of 126In, 125Cd, and 123Pd were measured whereby the mass uncertainty of 123Pd was improved. This is the first reported measurement with a new storage ring mass spectrometry technique realized at a heavy-ion cyclotron and employing individual injection of the preidentified rare nuclei. The latter is essential for the future mass measurements of the rarest isotopes produced at RIBF. The impact of the new 123Pd result on the solar r-process abundances in a neutron star merger event is investigated by performing reaction network calculations of 20 trajectories with varying electron fraction Ye. It is found that the neutron capture cross section on 123Pd increases by a factor of 2.2 and β-delayed neutron emission probability, P1n, of 123Rh increases by 14%. The neutron capture cross section on 122Pd decreases by a factor of 2.6 leading to pileup of material at A = 122, thus reproducing the trend of the solar r-process abundances. The trend of the two-neutron separation energies (S2n) was investigated for the Pd isotopic chain. The new mass measurement with improved uncertainty excludes large changes of the S2n value at N = 77. Finally, such large increase of the S2n values before N = 82 was proposed as an alternative to the quenching of the N = 82 shell gap to reproduce r-process abundances in the mass region of A = 112 – 124.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP); USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
89233218CNA000001
OSTI ID:
2305308
Alternate ID(s):
OSTI ID: 1863843
Report Number(s):
LA-UR-21-30298
Journal Information:
Physical Review Letters, Vol. 128, Issue 15; ISSN 0031-9007
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
binding energy & masses
r-process
storage rings