Capture Reactions on Unstable Isotopes: Determining Unknown Cross Sections with Indirect Data and Theory

Abstract:  Cross sections for compound-nuclear reactions involving unstable targets are important for many applications, but can often not be measured directly. Several indirect methods have recently been proposed to determine neutron capture cross sections for unstable isotopes. These methods aim at constraining statistical calculations of capture cross sections with data obtained from the decay of the compound nucleus relevant to the desired reaction. Each method produces this compound nucleus in a dierent manner (via a light-ion reaction, a photon-induced reaction, or decay) and requires additional ingredients to yield the sought-after cross-section. This talk focuses on the process of determining capture cross sections from inelastic scattering and transfer experiments. Specifically, theoretical descriptions of the (p,d) and (d,p) transfer reaction have been developed to complement recent measurements in the Zr-Y-Mo region. The procedure for obtaining constraints for unknown capture cross sections is illustrated. Indirectly extracted cross sections for both known (benchmark) and unknown capture reactions are presented. The main advantages and challenges of this approach are compared to those of the proposed alternatives. * This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Partial support from the Laboratory Directed Research and Development Program at LLNL,Project No. 16-ERD-022 is acknowledged.