Total Absorption Spectroscopy of Ground and Isomeric States in ⁷⁰Cu

One of the underlying assumptions in astrophysical reaction rate calculations is the generalized Brink-Axel (gBA) hypothesis, which states that the γ-ray strength function (γSF) is independent of the initial excitation energy and spin of nuclear states in the compound nucleus. While the initial excitation energy independence of the gBA has been previously studied, the spin-independence remains untested. Here, we test the spin-independence of the gBA by investigating the β-decay of ⁷⁰Cu, which offers a unique opportunity to study the γSF over different spin ranges at similar excitation energies in the daughter nucleus. ⁷⁰Cu has three β-decaying spin-parity states (6⁻ ground state, and two isomeric states: 3⁻, and 1⁺). In an experiment performed at the National Superconducting Cyclotron Laboratory ⁷⁰Cu was produced, isolated by the Low-Energy Beam and Ion Trap (LEBIT), and then delivered to the Summing NaI (SuN) Total Absorption Spectrometer. Preliminary results from total absorption spectroscopy following the β-decay of each of the three β-decaying spin-parity states will be presented. The data will be used in future β-Oslo analysis to obtain γSF and nuclear level densities and test the spin-independence of the gBA hypothesis.