Masses of transuranium nuclides measured with the PI-ICR technique at TRIGA-Trap

Abstract

We have revisited the region of the actinides in the vicinity of the neutron number N=152 and conducted high-precision mass measurements using the newly implemented Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique. The masses of \(^{244}\)Pu and \(^{249}\)Cf were found to deviate by 5.4 and 2.9 combined sigmas, respectively, from our previous results published in 2014. This indicates the presence of systematic errors in the earlier measurements. Consequently, we decided to remeasure all the nuclides from our 2014 study, along with \(^{248}\)Cm, to ensure accuracy and reliability. With our greatly improved apparatus, we have measured the masses of \(^{244}\)Pu, \(^{241}\)Am, \(^{243}\)Am, \(^{248}\)Cm, and \(^{249}\)Cf, using \(^{208}\)Pb and \(^{238}\)U as mass references. The masses of these reference ions were recently determined with ultra-high precision at Pentatrap. Our results were implemented in the latest Atomic Mass Evaluation (AME), showing good consistency. The region related to the masses measured in this study, especially for isotopes near the N=152 deformed shell gap, is discussed in terms of two-neutron separation energies, first excited 2\(^+\) energy levels and their differentials, as well as \(\delta V_{pn}\) values, the average proton-neutron interaction of the most loosely bound two nucleons.