Reconciling differential radii in the silver chain through improved measurement and { ab initio} calculations

Nuclear charge radius differences in the silver isotopic chain have been reported through different combinations of experiment and theory, and clear disagreement is observed beyond the assigned uncertainties. This study investigates this issue by combining high-accuracy calculations for six low-lying states of atomic silver with an improved measurement of the 5s ²S1/2 - 5p ²P3/2 transition optical isotope shift. Our calculations predict measured electronic transition energies in Ag I at the 0.3% level, the highest accuracy achieved in this system so far. We calculate electronic isotope shift factors by employing analytical response relativistic coupled-cluster theory, and find that a consistent charge radius difference between 107,109Ag is returned when combining our calculations with the available optical isotope shift measurements. We therefore recommend an improved value for the mean-squared charge radius difference between ¹⁰⁷Ag and ¹⁰⁹Ag as $0.207(3)[4]$ fm², in marginal agreement with the value derived from muonic Ag experiments, and an updated set of charge radii differences across the isotopic chain.