Proton spectroscopy of 48Ni, 46Fe, and 44Cr

Results of decay spectroscopy on nuclei in the vicinity of the doubly magic Ni-48 are presented. The measurements were performed with a time projection chamber with optical readout which records tracks of ions and protons in the gaseous volume. Six decays of Ni-48, including four events of two-proton ground-state radioactivity, were recorded. An advanced reconstruction procedure yielded the 2p decay energy for Ni-48 of Q(2p) = 1.29(4) MeV. In addition, the energy spectra of beta-delayed protons emitted in the decays of Cr-44 and Fe-46, as well as half-lives and branching ratios, were determined. The results were found to be consistent with the previous measurements made with Si detectors. A new proton line in the decay of Cr-44 corresponding to the decay energy of 760 keV is reported. The first evidence for the beta 2p decay of Fe-46, based on one clear event, is shown.