Speaker
Description
The existence of the weak intermediate neutron-capture process (i-process) explains the observed astrophysical abundances of elements around the $Z<50$ region. Neutron capture reactions in the $A=70$ mass region for Ni, Cu, and Zn isotopes are known to produce large variations in predicted i-process abundances. Predicted stellar abundances of Ga are particularly affected by the $^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ reaction. The $\beta$-decay of ${}^{70}\mathrm{Cu}$ offers an unique opportunity to utilize the $\beta$-Oslo method to experimentally determine the $\gamma$-ray strength function and nuclear level density and constrain the ${}^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ reaction rate for i-process nucleosynthesis. ${}^{70}\mathrm{Cu}$ has three different $\beta$-decaying spin-parity states that populate different spin ranges at similar excitation energies in the daughter nucleus: the $6^-$ ground state, the $101\,\mathrm{keV}$ $3^-$ isomeric state, and the $242\,\mathrm{keV}$ $1^+$ isomeric state. In experiments performed at the NSCL and FRIB, the isomers and ground state of $^{70}\mathrm{Cu}$ were produced and delivered to the Low Energy Beam and Ion Trap (LEBIT) and then to Summing NaI (SuN) Total Absorption Spectrometer. Preliminary results from $\beta$-Oslo analysis will be presented along with the preliminary constrained ${}^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ cross-section. Initial results from the commissioning of the SuN upgrade (to SuN++) will also be presented.
