$\beta$-Delayed Proton Emission of $^{71}$Kr

Mirror nuclei and their decay properties are key in understanding the role of isospin in nuclear structure. The character of ground state and low-lying states in the Kr/Br mirror pair has been under debate. Properties of this mirror system were investigated in an implant-decay experiment at the NSCL using a beam containing $^{71}$Kr, produced by projectile fragmentation of a $^{92}$Mo beam on a Be target and purified with the RF Fragment Separator. The purified beam was implanted into the Beta-Counting Station surrounded by SeGA. A previously unobserved $\beta$-decay branch to the 407-keV state of $^{71}$Br, delayed proton decay to the 944-keV state of $^{70}$Se, as well as a precise measurement of the $^{71}$Kr half-life, will be presented. The intensity of observed 944-keV $\gamma$-ray transitions provides evidence that the spin of $^{71}$Kr must be greater than $J^{\pi}$ = 3/2-