Probing the Limits of Statistical Neutron Capture for the r Process: Experimental Constraints on 141Cs Nuclear Level Densities

Authors

• B. Greaves, University of Guelph
• D. Mücher, University of Guelph
• A. Spyrou, Facility for Rare Isotope Beams
• S. Goriely, Université Libre de Bruxelles
• D. Rochman, Paul Scherrer Institut
• H. C. Berg, Facility for Rare Isotope Beams
• D. L. Bleuel, Lawrence Livermore National Laboratory
• J. A. Clark, Argonne National Laboratory
• C. Dembski, University of Notre Dame
• Paul A. DeYoung, Hope CollegeFollow
• E. Good, Facility for Rare Isotope Beams
• C. M. Harris, Facility for Rare Isotope Beams
• A. J. Koning, International Atomic Energy Agency, Vienna
• A. C. Larsen, Universitetet i Oslo
• S. N. Liddick, Facility for Rare Isotope Beams
• S. M. Lyons, Pacific Northwest National Laboratory
• M. Markova, Universitetet i Oslo
• M. J. Mogannam, Facility for Rare Isotope Beams
• G. Owens-Fryar, Facility for Rare Isotope Beams
• A. Palmisano-Kyle, Tickle College of Engineering

Document Type

Article

Publication Date

12-1-2025

Publication Source

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

Volume Number

871

ISSN

03702693

Article Number

139992

Abstract

The r -process abundance peaks, particularly near mass number A ∼ 130, reflect underlying nuclear structure effects such as closed neutron shells, yet modeling the nucleosynthesis in this region remains hindered by uncertain neutron-capture rates. These rates are especially sensitive to nuclear level densities (NLDs) and γ -ray strength functions of neutron-rich nuclei, where experimental data are scarce. We present the first experimental constraint on the NLD of ¹⁴¹Cs using the β -Oslo method, extending sensitivity to the neutron-rich regime near the N=82 closed shell. Our data allow for critical calibration of microscopic NLD models and reveal that ¹⁴¹Cs lies near the limit of statistical model applicability. Using this experimental input, we evaluate radiative neutron-capture rates across neighboring isotones using both Hauser–Feshbach (HF) and High Fidelity Resonance (HFR) models. Our results show order-of-magnitude rate increases for nuclei along the N=86 line, signaling a transition to resonance-dominated capture in this region. These findings underscore the importance of constraining NLDs to improve r -process reaction network predictions, particularly in environments where the validity of statistical models breaks down.

Keywords

Nuclear level density, R process, Statistical capture, β-Oslo method

Recommended Citation

Published in: Physics Letters Section B Nuclear Elementary Particle and High Energy Physics, Volume 871, December 1, 2025.