Relativistic many-body calculations of the hyperfine-structure intervals in caesium and francium atoms

The hyperfine structure of caesium and francium levels has been calculated using the relativistic Hartree-Fock (RHF) method and with the correlations being taken into account by means of the many-body perturbation theory. The hyperfine interaction has been included in the Hartree-Fock equations. The effect of the finite size of the nucleus has been considered. For the s and p 1/2 states, the agreement of the authors' calculations with experiment is not worse than 3%. Using the experimental data on hyperfine structure the magnetic moments of isotopes 208-213 Fr are obtained.