Theoretical Analysis of the Hyperfine Structure of Alkali Atoms

The hyperfine interaction in the alkali-atom series has been investigated quantitatively. In particular, both core-polarization and relativistic effects have been taken into consideration explicitly. The former effect was studied using the moment-perturbation procedure while relativistic Hartree-Fock theory was used for the latter. The core polarization contribution was found to be nearly constant for all the alkali atoms at about 23% of the nonrelativistic restricted Hartree-Fock value. Relativistic corrections were found to be 0.25, 0.68, 2.18, 15.6, and 20.5%, respectively, for lithium, sodium, potassium, rubidium, and cesium. The theoretical results are compared with experimental hyperfine constants to obtain an assessment of the importance of many-body effects in these atoms.