Precise Mass Measurement of the 149La-149Ce-149Pr isobaric chain
Abstract
Penning trap mass measurements of 149La, 149Ce, and 149Pr were performed with the Canadian Penning Trap (CPT) at the CARIBU facility of Argonne National Laboratory using the phase-imaging ion-cyclotron-resonance technique. The resulting mass excess of 149La differs by 221 keV from a recent JYFLTRAP measurement, resulting in a significant change in the profile of the two-neutron separation energy for that isotopic chain. The mass excesses of 149Ce and 149Pr are determined with an eight-fold improvement in precision compared to previous time-of-flight ion-cyclotron-resonance measurements; the 149Ce value is consistent with AME2020, while the 149Pr mass excess is lower by 17.5 keV. The mass excesses of 149La and 149Pr reported in this work have been confirmed recently by a measurement with a multi-reflection time-of-flight mass spectrometer coupled to a β-time of flight detector at RIKEN, providing further validation of the present results.
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