  We report on our calculations of differential hyperfine anomalies in the
nuclear single-particle model for a number of atoms and ions of interest for
studies of fundamental symmetries violations. Comparison with available
experimental data allows one to discriminate between different nuclear
magnetization models, and this data supports the use of the nuclear
single-particle model over the commonly-used uniform ball model. Accurate
modelling of the nuclear magnetization distribution is important for testing
atomic theory through hyperfine comparisons. The magnetization distribution
must be adequately understood and modelled, with uncertainties well under the
atomic theory uncertainty, for hyperfine comparisons to be meaningful. This has
not been the case for a number of atoms of particular interest for precision
studies, including Cs. Our work demonstrates the validity of the nuclear
single-particle model for Cs, and this has implications for the theory analysis
of atomic parity violation in this atom.

Atomic Physics