Speaker
Description
We propose the $\gamma\gamma$ spectroscopy of $^{77,79}$Cu, which is of paramount interest for tracing the evolution of proton single-particle levels near $^{78}$Ni. Despite the limited resolution of the Dali-2 scintillators during the Seastar campaign, a level scheme could be constructed for $^{79}$Cu. The $\pi f_{7/2}$ strength turned out to be fairly fragmented, resulting in a level population and a decay pattern that was richer than anticipated. Spin assignments were suggested only from comparison with MCSM calculations. A more precise determination of the level feedings would enable for exclusive cross sections to be obtained, with together with a refined level scheme would constrain the possible spin values. To this purpose the improved resolution of a germanium array of 1%, against 9% for Dali-2, is particularly significant.
Since Seastar the intensity of the primary $^{238}$U beam has increased from 12 to 40 pnA, which compensates the lower $\gamma$ efficiency of 9% instead of 27% (after addback). We would retain the Minos liquid hydrogen target with its TPC for identifying proton knock-out on an incoming zinc beam. We expect we would need the same amount of beam time as was used for Seastar, that is 5.5 days.
The study of particle-hole states in $^{80}$Zn, such as the $g_{9/2}^{-1} d_{5/2}$ neutron multiplet that breaks the $N=50$ core, would inform us on the size of the eponymous shell gap. They would be accessed through neutron knock-out from a $^{81}$Zn beam, for which a different but nearby setting of the spectrometer should be chosen. The beam-time estimate for this measurement equals 3 days.
