Half-Life Measurements of Bare, Mass-Resolved Isomers in a Storage-Cooler Ring

Secondary beams from fragmentation of $^{58}\mathrm{Ni}$ have been produced with energies of $(200\ensuremath{-}220)A$ MeV, separated with a fragment separator and injected into a storage-cooler ring for half-life measurements. The relative momentum spread $\frac{\ensuremath{\Delta}p}{p}\ensuremath{\approx}1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ (FWHM) which we achieved allowed us to resolve the ground and isomeric states of cooled $^{52}\mathrm{Mn}$ and $^{53}\mathrm{Fe}$ nuclei in the measured mass spectra. The circulating beams were fully ionized, which rendered it possible to measure pure ${\ensuremath{\beta}}^{+}$ branches for $^{52g}\mathrm{Fe}$ and $^{53g}\mathrm{Fe}$ and the sum of pure ${\ensuremath{\beta}}^{+}$ and $\ensuremath{\gamma}$ branches in the decay of the isomers $^{52m}\mathrm{Mn}$ and $^{53m}\mathrm{Fe}$.