Precise Mass Measurement of the ${}^{149}$La-${}^{149}$Ce-${}^{149}$Pr isobaric chain

Abstract

Penning trap mass measurements of ${}^{149}$La, ${}^{149}$Ce, and ${}^{149}$Pr 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 ${}^{149}$La 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 ${}^{149}$Ce and ${}^{149}$Pr are determined with an eight-fold improvement in precision compared to previous time-of-flight ion-cyclotron-resonance measurements; the ${}^{149}$Ce value is consistent with AME2020, while the ${}^{149}$Pr mass excess is lower by 17.5 keV. The mass excesses of ${}^{149}$La and ${}^{149}$Pr reported in this work have been confirmed recently by a measurement with a multi-reflection time-of-flight mass spectrometer coupled to a ${\hat{I}}^2$-time of flight detector at RIKEN, providing further validation of the present results.

6 pages, 4 figures