Abstract
Background: Neutron capture cross sections are essential to understanding the astrophysical and 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 , 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 and estimated uncertainties are below about 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 -process nucleosynthesis.
- Received 30 June 2017
DOI:https://doi.org/10.1103/PhysRevC.96.061601
©2017 American Physical Society