Ground-state and decay properties of neutron-rich 106Nb

TL;DR

This study precisely measured the ground-state mass, decay half-life, and level scheme of neutron-rich 106Nb, providing new insights into its nuclear structure and decay properties, and challenging previous spin-parity assignments.

Contribution

The paper presents the most precise mass excess measurement of 106Nb and expands the decay scheme of 106Mo, also revising the ground-state spin-parity of 106Nb based on new decay data.

Findings

Mass excess of 106Nb measured as -66202.0(13) keV with improved precision.

Decay half-life of 106Nb found to be 1.097(21) seconds, slightly longer than previous values.

Expanded level scheme of 106Mo up to 4 MeV, suggesting a revision of 106Nb's ground-state spin-parity.

Abstract

The ground-state properties of neutron-rich 106Nb and its beta 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 beta-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, beta-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 approximately 4 MeV. The distribution of decay strength and considerable population of excited states in 106Mo of J >= 3 emphasises the need to revise the adopted Jpi = 1- ground-state spin-parity assignment of 106Nb; it is more likely to be J => 3.