Ground-state and decay properties of neutron-rich Nb106

Abstract

The ground-state properties of neutron-rich 106Nb and its β decay into 106Mo have been studied using the CARIBU radioactive-ion-beam facility at Argonne National Laboratory. Niobium-106 ions were extracted from a 252Cf fission source and mass separated before being delivered as low-energy beams to the Canadian Penning Trap, as well as the X-Array and SATURN β-decay-spectroscopy station. The measured 106Nb ground-state mass excess of −66202.0(13) keV is consistent with a recent measurement but has three times better precision; this work also rules out the existence of a second long-lived, β-decaying state in 106Nb above 5 keV in excitation energy. The decay half-life of 106Nb was measured to be 1.097(21) s, which is 8% longer than the adopted value. The level scheme of the decay progeny, 106Mo, has been expanded up to ≈4MeV. The distribution of decay strength and considerable population of excited states in 106Mo of J≥3 emphasizes the need to revise the adopted Jπ=1− ground-state spin-parity assignment of 106Nb; it is more likely to be J≥3.