Level Densities and Gamma-Ray Strengths Inferred from Ground and Isomeric States in ⁷⁰Cu

One of the fundamental assumptions involved in calculations of astrophysical rates and neutron-capture cross sections is the generalized Brink-Axel hypothesis. This states that the gamma-ray strength function (γSF) is independent of how the initial compound nucleus is formed with respect to the initial excitation energy, spin, or parity. Here we test this hypothesis on the basis of the spin-independence of the γSF using ⁷⁰Cu, which has three β-decaying isomeric states with spins of 6^-, 3^-, and 1⁺ for the ground state, 101 keV-state, and 242-keV state, respectively. ⁷⁰Cu ions were produced at the National Superconducting Cyclotron Laboratory and thermalized in the gas stopper before being transmitted to the Low-Energy Beam Ion Trap Facility (LEBIT), where the isomers were separated based on mass through the LEBIT ion trap. Specific isomers were then delivered from the trap into the Summing NaI (SuN) total absorption spectrometer, where the γSF and nuclear level density (NLD) can be obtained using the β-Oslo method, an indirect technique for constraining neutron-capture cross sections. Preliminary results on the experimental isomer ratios, γSF, and NLD will be presented.