Charge radii in francium isotopes

Nuclear distributions affect many aspects of atomic spectra, making atomic physics a useful tool to study also nuclear properties. Relativistic couple d-cluster calculations for the 7s and 7p states in Fr are presented and app lied to binding energies, and to electronic factors for the field isotope s hift. The result, Fk = 21.0 GHz fm(2) for the 7s-7p(3/2) transition, leads to revised values for the changes in charge radius for the francium isotope s.