Strength of nuclear shell effects at N=126 in the r-process region

Journal Article · Sat Apr 15 00:00:00 EDT 2006 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PhysRevC.73.045803· OSTI ID:20771497

Farhan, A R; Sharma, M M ^[1]

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1. Physics Department, Kuwait University, 13060 (Kuwait)

We have investigated nuclear-shell effects across the magic number N=126 in the region of the r-process path. Microscopic calculations have been performed using the relativistic Hartree-Bogoliubov approach within the framework of the relativistic mean-field (RMF) theory for isotopic chains of rare-earth nuclei in the r-process region. The Lagrangian model NL-SV1 with the inclusion of the vector self-coupling of {omega} meson has been employed. The RMF results show that the shell effects at N=126 remain strong and exhibit only a slight reduction in the strength in going from the r-process path to the neutron drip line. This is in striking contrast to a systematic weakening of the shell effects at N=82 in the r-process region predicted earlier in the similar approach. In comparison the shell effects with microscopic-macroscopic mass formulas show a near constancy of shell gaps leading to strong shell effects in the region of r-process path to the drip line. A recent analysis of solar-system r-process abundances in a prompt supernova explosion model using various mass formulas, including the recently introduced mass tables based on Hartree-Fock-Bogoliubov method shows that although mass formulas with weak shell effects at N=126 give rise to a spread and an overproduction of nuclides near the third abundance peak at A{approx}190, mass tables with droplet models showing stronger shell effects are able to reproduce the abundance features near the third peak appropriately. In comparison, several analyses of the second r-process peak at A{approx}130 have required weakened (quenched) shell effects at N=82. Our predictions in the RMF theory with NL-SV1, which exhibit weaker shell effects at N=82 and correspondingly stronger shell effects at N=126 in the r-process region, support the conjecture that a different nature of the shell effects at the magic numbers may be at play in r-process nucleosynthesis of heavy nuclei.

• OSTI ID: 20771497
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 73, Issue 4; Other Information: DOI: 10.1103/PhysRevC.73.045803; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
COMPARATIVE EVALUATIONS
COUPLING
DROPLET MODEL
ELEMENT ABUNDANCE
HARTREE-FOCK-BOGOLYUBOV THEORY
HEAVY NUCLEI
LAGRANGIAN FUNCTION
MAGIC NUCLEI
MASS FORMULAE
MEAN-FIELD THEORY
NEUTRONS
NUCLEOSYNTHESIS
OMEGA-782 MESONS
R PROCESS
RARE EARTH NUCLEI
RELATIVISTIC RANGE
SOLAR SYSTEM