β decay of the $T_z=-1/2$ nuclide ${}^{71}\mathrm{Kr}$ has been studied at the ISOLDE PSB Facility at CERN. ${}^{71}\mathrm{Kr}$ ions were produced in spallation reactions in a Nb foil using the 1 GeV proton beam and studied by means of β-delayed proton, β- and γ-ray spectroscopy. The half-life and the β-decay energy of ${}^{71}\mathrm{Kr}$ were determined using the decay of protons and positrons. These results: $T_{1/2}=100\mathrm{}\pm 3\mathrm{ms}$ and $Q_{\mathrm{EC}}=10.14\mathrm{}\pm 0.32\mathrm{}\mathrm{MeV}$ and the first observation of the β branch to the 207 keV level in ${}^{71}\mathrm{Br}$ makes the extension of the systematics of Gamow-Teller matrix elements of mirror nuclei up to $A=71\mathrm{}$ possible. The Gamow-Teller strength of the same magnitude as that of the $\mathrm{fp}$-shell mirror nuclei is observed for the ground-state transition.

• Received 25 October 1996

DOI:https://doi.org/10.1103/PhysRevC.56.745