Total absorption spectroscopy of two isomers in $^{70}Cu influencing nucleosynthesis signatures

E. K. Ronning, K. Childers, G. Owens-Fryar, A. Richard, S. Liddick, A. Spyrou, I. Yandow, R. Ringle, A. Gross, G. W. Misch, S. Cupp, M. Mumpower, B. A. Brown, A. Chester, P. DeYoung

Published PRC 113 055802 (2026)

Isomers have long been known to be important for astrophysical nucleosynthesis processes, yet they are often neglected in network calculations due to computational limitations or lack of data. "Astromers" are astrophysically metastable nuclear states that can greatly impact nucleosynthesis pathways. In this work we show that astromers further impact the time-dependent electromagnetic signal during heavy element nucleosynthesis. In an experiment performed at the National Superconducting Cyclotron Laboratory, three $\beta$-decaying states of $^{70}Cu (6− ground state, and two isomeric states: 3− and 1+) were produced. $\beta$-feeding values were extracted from experimental spectra and compared to shell-model and QRPA+PVC calculations. Average $\gamma$-ray energies from the $\beta$-decay events were incorporated into simulations of heavy element nucleosynthesis and were found to exhibit different energy release profiles over time, which may impact, in aggregate, time-dependent observable signals.