High-Precision Mass Measurements of Neutron Deficient Silver Isotopes Probe the Robustness of the N=50 Shell Closure

High-precision mass measurements of exotic Ag95-97 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 Ag95 was directly determined for the first time. In addition, the atomic masses of β-decaying 2+ and 8+ states in Ag96 have been identified and measured for the first time, and the precision of the Ag97 mass has been improved. The newly measured masses, with a precision of ≈1 keV/c2, 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 ab initio calculations with various chiral effective field theory Hamiltonians. The precise determination of the excitation energy of the Ag96m isomer in particular serves as a benchmark for ab initio predictions of nuclear properties beyond the ground state, specifically for odd-odd nuclei situated in proximity to the proton dripline below Sn100. In addition, density functional theory calculations and configuration-interaction shell-model 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 dripline.