Theoretical hyperfine splittings of Be2+7,9 ions for future studies of nuclear properties

The authors demonstrate that higher-order quantum-electrodynamic calculations improve the accuracy of theoretical hyperfine splittings for heliumlike beryllium by two orders of magnitude. The consequent sensitivity to the nuclear Zemach radius and electric quadrupole moment opens the way to measurements of these nuclear properties to an accuracy of 5% or better; thus providing a critical test of nuclear structure models, especially for the isotope ${}^{7}$Be.