Parity Measurements in $^{80}$Sr

Until recently, $^{80}$Sr was thought to possess only positive-parity states, in contrast to many other neighboring nuclei which are known to have negative-parity states. Now there is indirect experimental evidence for negative-parity states, but the parities have not been measured directly. The goal of this study was to finally resolve this long-standing mystery by measuring conclusively the parities of as many excited states in $^{80}$Sr as possible. $^{80}$Sr nuclei were produced at Florida State University following the $^{54}$Fe($^{28}$Si, 2$p$) and the $^{54}$Fe($^{28}$Si, $\alpha$2$p$) reactions at 90 and 110 MeV, respectively. Following the reactions, high-spin states in $^{80}$Sr were populated and data were collected on the resulting cascades of emitted $\gamma$ rays using an array of 10 Ge detectors. The linear polarizations of 31 $\gamma$ rays were measured and many times allowed for the determination of the parity of the parent state that released the $\gamma$ ray. The results have conclusively verified negative parity for one sequence of states, and positive parity for the yrast states.