Probing the limits of statistical neutron capture for the r process: Experimental constraints on 141Cs nuclear level densities

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 <sup>141</sup>Cs 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 <sup>141</sup>Cs 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.

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Publication Details

Journal
Physics Letters B
Published
2025-11-05
DOI
https://doi.org/10.1016/j.physletb.2025.139992
Primary Topic
Nuclear physics research studies
Type
article
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article

Probing the limits of statistical neutron capture for the r process: Experimental constraints on 141Cs nuclear level densities

A. Tsantiri, G. Savard, G. Owens-Fryar, M. Markova et al.
Physics Letters B
Nuclear physics research studies
article

Probing the limits of statistical neutron capture for the r process: Experimental constraints on 141Cs nuclear level densities

A. Tsantiri, G. Savard, G. Owens-Fryar, M. Markova, A. C. Larsen, J. A. Clark, D. Mücher, B. Greaves, C. Dembski, Howard C. Berg, M.K. Smith, E. Good, Chris Harris, A. Richard, M. J. Mogannam, S. Goriely, D. L. Bleuel, A. Spyrou, S. Lyons, A. Palmisano-Kyle, S. N. Liddick, A. J. Koning, D. Santiago-Gonzalez, E. K. Ronning, A. Sweet, D. Rochman, P.A. DeYoung
article en

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 <sup>141</sup>Cs 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 <sup>141</sup>Cs 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.

Physics Letters BVol. 871
Openalex Percentile: Top 85%
Nuclear physics research studies
DOIOpen Access PDFOpenAlex
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