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Simple, empirical approach to predict neutron capture cross sections from nuclear masses

A. Couture, R. F. Casten, and R. B. Cakirli
Phys. Rev. C 96, 061601(R) – Published 20 December 2017

Abstract

Background: Neutron capture cross sections are essential to understanding the astrophysical s and r processes, the modeling of nuclear reactor design and performance, and for a wide variety of nuclear forensics applications. Often, cross sections are needed for nuclei where experimental measurements are difficult. Enormous effort, over many decades, has gone into attempting to develop sophisticated statistical reaction models to predict these cross sections. Such work has met with some success but is often unable to reproduce measured cross sections to better than 40%, and has limited predictive power, with predictions from different models rapidly differing by an order of magnitude a few nucleons from the last measurement.

Purpose: To develop a new approach to predicting neutron capture cross sections over broad ranges of nuclei that accounts for their values where known and which has reliable predictive power with small uncertainties for many nuclei where they are unknown.

Methods: Experimental neutron capture cross sections were compared to empirical mass observables in regions of similar structure.

Results: We present an extremely simple method, based solely on empirical mass observables, that correlates neutron capture cross sections in the critical energy range from a few keV to a couple hundred keV. We show that regional cross sections are compactly correlated in medium and heavy mass nuclei with the two-neutron separation energy. These correlations are easily amenable to predict unknown cross sections, often converting the usual extrapolations to more reliable interpolations. It almost always reproduces existing data to within 25% and estimated uncertainties are below about 40% up to 10 nucleons beyond known data.

Conclusions: Neutron capture cross sections display a surprisingly strong connection to the two-neutron separation energy, a nuclear structure property. The simple, empirical correlations uncovered provide model-independent predictions of neutron capture cross sections, extending far from stability, including for nuclei of the highest sensitivity to r-process nucleosynthesis.

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  • Received 30 June 2017

DOI:https://doi.org/10.1103/PhysRevC.96.061601

©2017 American Physical Society

Physics Subject Headings (PhySH)

Nuclear Physics

Authors & Affiliations

A. Couture*

  • Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

R. F. Casten

  • Wright Laboratory, Yale University, New Haven, Connecticut 06520, USA and Michigan State University–Facility for Rare Isotope Beams (MSU-FRIB), East Lansing, Michigan 48823, USA

R. B. Cakirli

  • Department of Physics, University of Istanbul, Istanbul, Turkey

  • *Corresponding author: acouture@lanl.gov

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Issue

Vol. 96, Iss. 6 — December 2017

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