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

Author:

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

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex), Nuclear Theory (nucl-th)

journal:

date:

2024-01-15 00:00:00

Abstract

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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