Zhuang Ge [1,2], Mikael Reponen [1], Tommi Eronen [1], Baishan Hu [3,4,5], Markus Kortelainen [1], Anu Kankainen [1], Iain Moore [1], Dmitrii Nesterenko [1], Cenxi Yuan [6], Olga Beliuskina [1], Laetitia Cañete, Ruben de Groote [1,7], Celement Delafosse [1,8], Pierre Delahaye [9], Timo Dickel [2,10], Antoine de Roubin [1], Sarina Geldhof [1,9], Wouter Gins [1], Jason Holt [3,11], Marjut Hukkanen [1,12], Arthur Jaries [1], Ari Jokinen [1,7,13,14,10], Ã\udc81gota Koszorús, Gabriella Kripkó-Koncz, Sonja Kujanpää, Yihua Lam [15,16], Stylianos Nikas [1], Alejandro Ortiz-Cortes [1,9], Heikki Penttilä, Daniel Pitman-Weymouth [1,2,10], Wolfgang Plaß, Ilkka Pohjalainen [1], Andrea Raggio [1], Sami Rinta-Antila [1], Jorge Romero [1,13], Marek Stryjczyk [1], Markus Vilen [1,14], Ville Virtanen [1], Alexandra Zadvornaya [1]
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 $β$-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. Empirical shell-gap and pairing energies determined with the new ground-state mass data are compared with the state-of-the-art \textit{ab initio} calculations with various chiral effective field theory Hamiltonians. The precise determination of the excitation energy of the $^{96m}$Ag isomer in particular 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. 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.