Identification and investigation of possible ultra-low Q value β decay candidates

Among the wide energy range of β decays, there can exist decays with Q values as low as a few hundred eV. These decays can occur when the parent decays to a excited state in the daughter nucleus. Such decays have been called “ultra-low” Q value β decays. Their application is mainly twofold: (1) they are of interest as potential candidates for neutrino mass determination experiments, and (2) they provide a testing ground for theoretical studies of atomic interference effects in the nuclear decay process. In this work we have identified a number of such potential candidates by analyzing the most recent atomic mass and nuclear energy level data. To determine if an ultra-low Q value β decay branch is energetically allowed for these candidates, more precise and accurate data for the Q value of the ultra-low decay branch is needed. In most cases, this requires more precise atomic mass measurements for the parent and/or daughter atoms. These requirements can be met using Penning trap mass spectrometry.