High-precision mass measurements of neutron deficient silver isotopes probe the robustness of the $N$ = 50 shell closure

Z. Ge, M. Reponen, T. Eronen, B. S. Hu, M. Kortelainen, A. Kankainen, I. D. Moore, D. A. Nesterenko, C. X. Yuan, O. Beliuskina, L. Cañete, R. de Groote, C. Delafosse, P. Delahaye, T. Dickel, A. de Roubin, S. Geldhof, W. Gins, J. D. Holt, M. Hukkanen, A. Jaries, A. Jokinen, Á. Koszorús, G. Kripko-Koncz, S. Kujanpää, Y. H. Lam, S. Nikas, A. Ortiz-Cortes, H. Penttilä, D. Pitman-Weymouth, W. Plaß, A. Raggio, S. Rinta-Antila, J. Romero, M. Stryjczyk, M. Vilen, V. Virtanen, A. Zadvornaya
Nuclear Experiment, Nuclear Experiment (nucl-ex), Nuclear Theory (nucl-th)
2024-01-15 00:00:00
High-precision mass measurements of exotic $^{95-97}$Ag isotopes close to the $N = Z$ line have been conducted with the JYFLTRAP double Penning trap mass spectrometer, with the silver ions produced using the recently commissioned inductively-heated hot cavity catcher laser ion source at the Ion Guide Isotope Separator On-Line facility. The atomic mass of $^{95}$Ag was directly determined for the first time. In addition, the atomic masses of $\beta$-decaying 2$^+$ and 8$^+$ states in $^{96}$Ag have been identified and measured for the first time, and the precision of the $^{97}$Ag mass has been improved. The newly measured masses, with a precision of $\approx$ 1 keV/c$^2$, have been used to investigate the $N =$ 50 neutron shell closure confirming it to be robust. Precise empirical shell-gap and pairing energies determined with the new ground-state mass data are used to benchmark state-of-the-art \textit{ab initio} calculations with various chiral effective field theory Hamiltonians. In addition, density functional theory (DFT) calculations and configuration-interaction shell-model (CISM) calculations are compared with the experimental results. All theoretical approaches face challenges to reproduce the trend of nuclear ground-state properties in the silver isotopic chain across the $N =$50 neutron shell and toward the proton drip-line. Furthermore, the precise determination of the isomeric excitation energy of $^{96m}$Ag serves as a benchmark for \textit{ab initio} predictions of nuclear properties beyond the ground state, specifically for odd-odd nuclei situated in proximity to the proton dripline below $^{100}$Sn.
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