β-decay half-lives of very neutron-rich isotopes of elements from Ti to Ni

Abstract:

The unknown β-decay half-lives of 22 isotopes far off stability (5 < T _Z < 10) in the region from Ti to Ni were measured at GSI, Darmstadt. The nuclei were produced in a fragmentation reaction of 500 A.MeV ⁸⁶Kr-projectile impinging on a thick Be target. The isotopes of interest were separated and identified with the fragment separator, FRS, by a combination of Bρ,Z, and ToF techniques. An additional range separation was performed by a selective implantation into granular detectors. The spatial and time correlations of the implant with the consecutively detected β-particles were used to determine the unknown half-lives. For nuclei far off stability, β-decay chains were measured and analyzed as well, leading to an even more reliable evaluation of the lifetimes. The large discrepancies found between the measured and the theoretical values emphasize that most recent theoretical work is not an improvement over calculations made almost a decade ago.