The ${\beta }^{+}$ decay of ${}_{}{}^{47}{}_{}{}^{}\mathrm{Cr}$ ($J^{\pi }$,T${=(3/2)\mathrm{}}^{\mathrm{-}}$,(1/2)) has been studied following its production by the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$${(}^{40}$Ca, 2n${)}^{47}$Cr reaction at E${(\mathrm{}}^{40}$Ca)≊90 MeV. In addition to the previously reported superallowed decay to the mirror state (i.e., the ${}_{}{}^{47}{}_{}{}^{}\mathrm{V}$ ground state), we observe a (3.7±1.2)% allowed ${\beta }^{+}$ branch to the ${\mathrm{}(5/2)\mathrm{}}^{\mathrm{-}}$ state at 87 keV in ${}_{}{}^{47}{}_{}{}^{}\mathrm{V}$. These two branches appear to dominate the decay of ${}_{}{}^{47}{}_{}{}^{}\mathrm{Cr}$; an upper limit of less than 0.5% is set on possible γ rays, other than the 87-keV γ ray, in the range of 15 to 2800 keV. Measurement of the time decay of the 87-keV γ ray establishes a value of $T_{1/2}$=508±10 ms for the ${}_{}{}^{47}{}_{}{}^{}\mathrm{Cr}$ half-life which is in significant disagreement with two previously reported values. The present work utilized Ge spectroscopy and a He-jet system for transport of the beam-induced radioactivity, as opposed to previous measurements which used a plastic scintillator to detect positrons and either a He-jet chopper or a slow beam-pulsing system. A summary of decay data for the complete $f_{7/2}$ shell series of mirror nuclei is also presented.

• Received 7 January 1985

DOI:https://doi.org/10.1103/PhysRevC.31.1490