First observation of the T-z=-7/2 nuclei Fe-45 and Ni-49

A primary beam of Ni-58 at 600 MeV/nucleon from the SIS synchrotron at GSI was used to produce proton-rich isotopes in the titanium-to-nickel region by projectile fragmention on a beryllium target. The fragments were separated by a projectile-fragement separator and unambiguously identified. We report here the first observation of the T-z = -7/2 nuclei Fe-45 and Ni-49, the most proton-rich nuclei ever synthesized with an excess of seven protons. Tn addition, the new isotope Cr-42 (T-z = -3) was identified. According to commonly used mass predictions, these isotopes are all unbound with respect to two-proton emission from their ground states. From the nonobservation of Ti-38 (T-z = -3) in this experiment, an upper limit of 120 ns is deduced for the half-life of this isotope.