Precise Mass Measurements of $A=133$ Isobars with the Canadian Penning Trap: Resolving the $Q_{β^-}$ anomaly at ${}^{133}$Te

Abstract

We report precision mass measurements of ${}^{133}$Sb, ${}^{133g,m}$Te, and ${}^{133g,m}$I, produced at CARIBU at Argonne National Laboratory's ATLAS facility and measured using the Canadian Penning Trap mass spectrometer. These masses clarify an anomaly in the ${}^{133}$Te ${\hat{I}}^2$-decay. The masses reported in the 2020 Atomic Mass Evaluation (M. Wang et al., 2021) produce $Q_{β^-}(^{133}$Te)=2920(6) keV; however, the highest-lying ${}^{133}$I level populated in this decay is observed at $E_i=2935.83(15)$ keV, resulting in an anomalous $Q_{β^{-}}^{i}=-16(6)$~keV. Our new measurements give $Q_{β^-}(^{133}\text{Te})=2934.8(11)$ keV, a factor of five more precise, yielding $Q{_β^i}=-1.0(12)$~keV, a 3$\ddot{I}ƒ$ shift from the previous results. This resolves this anomaly, but indicates further anomalies in our understanding of the structure of this isotope.

5 pages, 3 figures